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Total and sectional gas-phase holdups are measured in a wide (0.305 m internal diameter) and long (3.7 m) glass bubble column al ambient conditions as a function of superficial gas velocity. Sectional gas holdup values vary along the length of the column and decrease as the height above the gas distributor plate increases in the transitional and turbulent flow regimes.
L. Z. PINO; R. B. SOLARI; S. SIQUIER; L. ANTONIO ESTèVEZ; M. M. YèPEZ; A. E. SêEZ
This work presents experimental data on gas holdup in slurry bubble columns with a foaming liquid. The effects of solids concentration, solid particle size, superficial phase velocities and column dimensions on the gas holdup are analyzed. At low superficial gas velocities (less than 4cm\\/s), for which the liquid does not foam, the presence of solids with small particle size does
Gamma densitometry tomography of gas holdup spatial distribution in industrial scale bubble columns
Shollenberger, K.A.; Torczynski, J.R.; Adkins, D.R.; O`Hern, T.J.; Jackson, N.B.
Gamma-densitometry tomography (GDT) experiments have been performed to measure gas holdup spatial variations in two bubble columns: a 0.19 m inside diameter Lucite column and a 0.48 m inside diameter stainless steel vessel. Air and water were used for the measurements. Horizontal scans at one vertical position in each column were made for several air flow rates. An axi-symmetric tomographic reconstruction algorithm based on the Abel transform has been used to calculate the time averaged gas holdup radial variation. Integration of these profiles over the column cross section has yielded area-averaged gas holdup results, which have been compared with volume-averaged gas holdups determined from differential pressure measurements and from the rise in the air/water interface during gas flow. The results agree reasonably well.
Novel correlations for gas holdup in large-scale slurry bubble column reactors operating under elevated pressures and temperatures
Arsam Behkish; Romain Lemoine; Rachid Oukaci; Badie I. Morsi
A comprehensive literature search was conducted to obtain the holdup data for different gases in various liquids and slurries using bubble and slurry bubble column reactors operating under wide ranges of conditions in different size reactors provided with a variety of gas spargers. The data were used to develop two novel correlations, one for the total gas holdup and the
Gas holdup and solids dispersion in a three-phase slurry bubble column
Dragomir B. Bukur; Shehal A. Patel; James G. Daly
Studies with three-phase systems in bubble columns have shown that the effect of solids on gas holdup depends on a variety of factors. Important among these are: liquid properties and particle properties such as density, size and concentration in the slurry, and wettability. Most of these studies have been made with cold flow systems; and the data at high temperatures
Gas holdup in slurry bubble columns: Effect of column diameter and slurry concentrations
Krishna, R.; Swart, J.W.A. de; Ellenberger, J.; Martina, G.B.; Maretto, C. [Univ. of Amsterdam (Netherlands). Dept. of Chemical Engineering] [Univ. of Amsterdam (Netherlands). Dept. of Chemical Engineering
In processes for converting natural gas to liquid fuels, bubble-column reactors are finding increasing application. To study the influence of particle concentration on the hydrodynamics of bubble-column slurry reactors operating in the heterogeneous flow regime, experiments were carried out in 0.10, 0.19, and 0.38-m-dia. columns using paraffinic oil as the liquid phase and slurry concentrations of up to 36 vol. %. To interpret experimental results a generalization of the two-phase model for gas-solid fluid beds was used to describe bubble hydrodynamics. The two phases identified are: a dilute phase consisting of fast-rising large bubbles that traverse the column virtually in plug flow and a dense phase that is identified with the liquid phase along with solid particles and entrained small bubbles. The dense phase suffers backmixing considerably. Dynamic gas disengagement was experimented in the heterogeneous flow regime to determine the gas voidage in dilute and dense phases. Experimental data show that increasing the solid concentration decreases the total gas holdup significantly, but the influence on the dilute-phase gas holdup is small. The dense-phase gas voidage significantly decreases gas holdup due to enhanced coalescence of small bubbles resulting from introduction of particles. The dense-phase gas voidage is practically independent of the column diameter. The dilute-phase gas holdup, on the other hand, decreases with increasing column diameter, and this dependence could be described adequately with a slight modification of the correlation of Krishna and Ellenberger developed for gas-liquid systems.
Phenomenological model for bubble column reactors: prediction of gas hold-ups and volumetric mass transfer coefficients
K. Shimizu; S. Takada; K. Minekawa; Y. Kawase
Based on a phenomenological model for bubble break-up and coalescence, a new simulation model for gas hold-up and gas-liquid mass transfer in bubble column reactors is proposed. In order to describe bubble movements in a bubble column reactor, a compartment concept is combined with the phenomenological model for bubble break-up and coalescence. It is assumed that the bubble column reactor
Influences of suspended fine particles on gas holdup and mass transfer characteristics in a slurry bubble column
Eizo Sada; Hidehiro Kumazawa; C. H. Lee
In this work, slurries with suspended fine particles (whose size is smaller than 10 ..mu..m) of lower than 1 wt. % were used to provide an insight into the solid-bubble interaction in a bubble column. The liquid property and the gas sparging system as well as the particle size were varied; the effects of these variables on the gas holdup
Cross-sectional distributions of gas and solid holdups in slurry bubble column investigated by ultrasonic computed tomography
M Warsito; M. Ohkawa; N. Kawata; S. Uchida
A brief review on recently developed non-invasive techniques for gasliquid and gasliquidsolid systems is presented first. The ultrasonic computed tomography (UCT) developed for measuring the time-averaged cross-sectional distributions of gas and solid holdups in a slurry bubble column is then described. The ultrasonic tomography is a coupling of the earlier developed transmission-mode ultrasonic technique with two-parameter sensing (the energy attenuation
Gas holdup and bubble size behavior in a large-scale slurry bubble column reactor operating with an organic liquid under elevated pressures and temperatures
Arsam Behkish; Romain Lemoine; Laurent Sehabiague; Rachid Oukaci; Badie I. Morsi
The holdups of small and large gas bubbles, bubble size distribution and the Sauter-mean bubble diameter were measured for N2 and He in isoparaffinic organic liquid mixture (Isopar-M) in the absence and presence of Alumina powder under various pressures (0.673MPa), temperatures (300473K), superficial gas velocities (0.070.39m\\/s), and solid concentrations (020vol.%) in a large-scale bubble column and slurry bubble column reactor
Local gas hold-up measurements in fluidized bed and slurry bubble column
J-M Schweitzer; J Bayle; T Gauthier
Fiber optic probes can be used to evaluate flow properties in gassolid and gasliquidsolid systems. In this study, the local flow structure of bubbling flow was investigated in a slurry bubble column and in a fluidized bed. The bubble flow characteristics could, therefore, be determined along the bed cross section in various operating conditions. In both systems, the results were
Gas holdup in slurry bubble columns: Effect of column diameter and slurry concentrations
Rajamani Krishna; Jeroen W. A. De Swart; J■rg Ellenberger; Gilbert B. Martina; Cristina Maretto
In processes for converting natural gas to liquid fuels, bubble-column reactors are finding increasing application. To study the influence of particle concentration on the hydrodynamics of bubble-column slurry reactors operating in the heterogeneous flow regime, experiments were carried out in 0.10, 0.19, and 0.38-m-dia. columns using paraffinic oil as the liquid phase and slurry concentrations of up to 36 vol.
Gas holdup in slurry bubble column reactors of a 150 t\\/d coal liquefaction pilot plant process
H. Ishibashi; M. Onozaki; M. Kobayashi; J.-i. Hayashi; H. Itoh; T. Chiba
Gas holdup data were obtained for three different kinds of coals in three coal liquefaction pilot plant reactors connected in series of the 150ton-coal\\/day NEDOL process. The gas holdup measured was correlated with the superficial gas velocity calculated by taking into account the vaporliquid equilibrium in the liquid or slurry phase at operating temperatures and pressures. The results showed that
Effect of operating variables on the gas holdup in a large-scale slurry bubble column reactor operating with an organic liquid mixture
Juan R. Inga; Badie I. Morsi
The effects of gas velocity, system pressure, and catalyst loading on gas holdup of Hã, Nã, CO, and CHã in an organic mixture of hexanes were investigated in a 0.316 m diameter, 2.8 m height slurry bubble column reactor operating with a commercial Fischer-Tropsch iron-based catalyst. The data were obtained in the churn-turbulent flow regime with catalyst loading up to
Holdup predictions for wet-gas pipelines compared
R. H. Shea; J. Rasmussen; P. Hedne; D. Malnes
In several predictive methods commonly used for wet-gas pipeline holdup, the magnitude of errors varies greatly. Comparison of these methods and their errors, given in this article, indicate that correlation-based methods should not be used for holdup prediction. Mechanistic models, on the other hand, yield better predictions of liquid holdup for hilly terrain pipelines. Test data from the Sintef Multiphase
Gas density effect on mass transfer in the slurry bubble column
I. Dewes; A. Schumpe
Gas holdups and volumetric mass transfer coefficients were studied in a bubble column varying the gas density by a factor of up to 300. The gas density effect increased with the gas velocity. A maximum effect was reached where the gas holdup (in water and in 0.8 M sodium sulfate solution) varied with the gas density to the power of
NASA Technical Reports Server (NTRS)
Mount, Bruce E. (Inventor); Burchfield, David E. (Inventor); Hagey, John M. (Inventor)
A gas bubble detector having a modulated IR source focused through a bandpass filter onto a venturi, formed in a sample tube, to illuminate the venturi with modulated filtered IR to detect the presence of gas bubbles as small as 0.01 cm or about 0.004 in diameter in liquid flowing through the venturi. Means are provided to determine the size of any detected bubble and to provide an alarm in the absence of liquid in the sample tube.
Experimental investigation of bubbling in particle beds with high solid holdup
Cheng, Songbai; Hirahara, Daisuke; Tanaka, Youhei; Gondai, Yoji; Zhang, Bin; Matsumoto, Tatsuya; Morita, Koji; Fukuda, Kenji [Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Yamano, Hidemasa; Suzuki, Tohru; Tobita, Yoshiharu [Advanced Nuclear System R and D Directorate, Japan Atomic Energy Agency, 4002 Narita, O-arai, Ibaraki 311-1393 (Japan)
A series of experiments on bubbling behavior in particle beds was performed to clarify three-phase flow dynamics in debris beds formed after core-disruptive accident (CDA) in sodium-cooled fast breeder reactors (FBRs). Although in the past, several experiments have been performed in packed beds to investigate flow patterns, most of these were under comparatively higher gas flow rate, which may be not expected during an early sodium boiling period in debris beds. The current experiments were conducted under two dimensional (2D) and three dimensional (3D) conditions separately, in which water was used as liquid phase, and bubbles were generated by injecting nitrogen gas from the bottom of the viewing tank. Various particle-bed parameters were varied, including particle-bed height (from 30 mm to 200 mm), particle diameter (from 0.4 mm to 6 mm) and particle type (beads made of acrylic, glass, alumina and zirconia). Under these experimental conditions, three kinds of bubbling behavior were observed for the first time using digital image analysis methods that were further verified by quantitative detailed analysis of bubbling properties including surface bubbling frequency and surface bubble size under both 2D and 3D conditions. This investigation, which hopefully provides fundamental data for a better understanding and an improved estimation of CDAs in FBRs, is expected to benefit future analysis and verification of computer models developed in advanced fast reactor safety analysis codes. (author)
Guerrero, H; Charles Crawford, C; Mark Fowley, M
Gas holdup tests were performed in bench-scale and small-scale mechanically-agitated mixing systems at the Savannah River National Laboratory (SRNL) for a simulant of waste from the Hanford Tank 241-AZ-101. These featured additions of DOW Corning Q2-3183A anti-foam agent. Results indicated that this anti-foam agent (AFA) increased gas holdup in the waste simulant by about a factor of four and, counter-intuitively, that the holdup increased as the non-newtonian simulant shear strength decreased (apparent viscosity decreased). Such results raised the potential of increased flammable gas retention in Hanford Waste Treatment and Immobilization Plant (WTP) vessels mixed by air sparging and pulse-jet mixers (PJMs) during a Design Basis Event (DBE). Additional testing was performed to determine the effects of simulant properties, composition of alternate AFAs, and presence of trace noble metals. Key results are that: (1) Increased gas holdup resulting from addition of Q2-3183A is due to a decrease in surface tension that supports small bubbles which have low rise velocities. (2) Dow Corning 1520-US AFA shows it to be a viable replacement to Dow Corning Q2-3183A AFA. This alternative AFA, however, requires significantly higher dosage for the same anti-foam function. (3) Addition of noble metals to the AZ-101 waste simulant does not produce a catalytic gas retention effect with the AFA.
Gas-liquid interfacial area and liquid-side mass-transfer coefficient in a slurry bubble column
Eizo Sada; Hidehiro Kumazawa; Choul Ho Lee; Hiroaki Narukawa
Influences of suspended particles upon such parameters as gas holdup, volumetric liquid-state mass-transfer coefficient, and gas-liquid interfacial area in a bubble column were investigated in sodium sulfite\\/sulfate solutions in which various loadings of coarse nylon particles and fine alumina particles were suspended. The volumetric mass-transfer coefficients and gas holdups were a bit increased by suspending a small amount of fine
S. SIQUIER; A. RONCHETTI; M. CALDERÆN; P. LLAGUNO; A. E. SêEZ
In this work we perform an experimental study of the spatial distribution of phases in slurry bubble columns with conical distributors that have a volume comparable to that of the cylindrical section. Three different distributors were used whose apex angles were 13¯, 22¯ and 34¯. In gas-liquid operation, the gas holdups are axially uniform in the cylindrical section and decrease
Large-Scale Testing of Effects of Anti-Foam Agent on Gas Holdup in Process Vessels in the Hanford Waste Treatment Plant
Mahoney, L.A.; Alzheimer, J.M.; Arm, S.T.; Guzman-Leong, C.E.; Jagoda, L.K.; Stewart, C.W.; Wells, B.E.; Yokuda, S.T. [Pacific Northwest National Laboratory, Richland, WA (United States)
The Hanford Waste Treatment and Immobilization Plant (WTP) will vitrify the radioactive wastes stored in underground tanks. These wastes generate and retain hydrogen and other flammable gases that create safety concerns for the vitrification process tanks in the WTP. An anti-foam agent (AFA) will be added to the WTP process streams. Previous testing in a bubble column and a small-scale impeller-mixed vessel indicated that gas holdup in a high-level waste chemical simulant with AFA was as much as 10 times higher than in clay simulant without AFA. This raised a concern that major modifications to the WTP design or qualification of an alternative AFA might be required to satisfy plant safety criteria. However, because the mixing and gas generation mechanisms in the small-scale tests differed from those expected in WTP process vessels, additional tests were performed in a large-scale prototypic mixing system with in situ gas generation. This paper presents the results of this test program. The tests were conducted at Pacific Northwest National Laboratory in a 1/4-scale model of the lag storage process vessel using pulse jet mixers and air spargers. Holdup and release of gas bubbles generated by hydrogen peroxide decomposition were evaluated in waste simulants containing an AFA over a range of Bingham yield stresses and gas generation rates. Results from the 1/4-scale test stand showed that, contrary to the small-scale impeller-mixed tests, holdup in the chemical waste simulant with AFA was not so greatly increased compared to gas holdup in clay without AFA. The test stand, simulants, scaling and data-analysis methods, and results are described in relation to previous tests and anticipated WTP operating conditions. (authors)
Large-Scale Testing of Effects of Anti-Foam Agent on Gas Holdup in Process Vessels in the Hanford Waste Treatment Plant - 8280
Mahoney, Lenna A.; Alzheimer, James M.; Arm, Stuart T.; Guzman-Leong, Consuelo E.; Jagoda, Lynette K.; Stewart, Charles W.; Wells, Beric E.; Yokuda, Satoru T.
The Hanford Waste Treatment Plant (WTP) will vitrify the radioactive wastes stored in underground tanks. These wastes generate and retain hydrogen and other flammable gases that create safety concerns for the vitrification process tanks in the WTP. An anti-foam agent (AFA) will be added to the WTP process streams. Prior testing in a bubble column and a small-scale impeller-mixed vessel indicated that gas holdup in a high-level waste chemical simulant with AFA was up to 10 times that in clay simulant without AFA. This raised a concern that major modifications to the WTP design or qualification of an alternative AFA might be required to satisfy plant safety criteria. However, because the mixing and gas generation mechanisms in the small-scale tests differed from those expected in WTP process vessels, additional tests were performed in a large-scale prototypic mixing system with in situ gas generation. This paper presents the results of this test program. The tests were conducted at Pacific Northwest National Laboratory in a ¥-scale model of the lag storage process vessel using pulse jet mixers and air spargers. Holdup and release of gas bubbles generated by hydrogen peroxide decomposition were evaluated in waste simulants containing an AFA over a range of Bingham yield stresses and gas gen geration rates. Results from the ¥-scale test stand showed that, contrary to the small-scale impeller-mixed tests, gas holdup in clay without AFA is comparable to that in the chemical waste simulant with AFA. The test stand, simulants, scaling and data-analysis methods, and results are described in relation to previous tests and anticipated WTP operating conditions.
Smith, D.N.; Ruether, J.A.; Stiegel, G.J.
A novel approach utilizing an electrical conductivity twin-probe technique is described for obtaining important gas-phase characteristics such as: bubble size, velocity ad holdup fraction. A 10 cm internal diameter by 310 cm height glass column is employed to investigate the bubble dynamics measured with this probe. The liquid phase is composed of a mixture of ethanol and water that may have substantial ''surface activity'' which results in a dynamic surface tension effect on the rate of bubble coalescence. Measurements of gas holdup, bubble size,and velocity indicate the influence of surface activity onthe gas phase characteristics. Possible implications of these results on the hydrodynamics of Fischer-Tropsch reactors are given. An experimental technique and subsequent analysis have been developed to determine the bubble size and velocity distributions in a slurry bubble column cold model. Dynamic surface tension effects have been observed for a two component liquid mixture. The maximum frothing ability of a ''surface-active'' species qualitatively agrees with a dynamic surface tension model. Increased gas holdup and interfacial area are observed with the addition of a ''surface-active'' component. In addition, increased gas holdup and interfacial area are observed with a sintered plate distributor compared to a perforated plate. The presence of solids reduces the gas holdup and increases the bubble size. 11 refs., 11 figs.
On sonoluminescence of an oscillating gas bubble
Harvey P. Greenspan; Ali Nadim
It is proposed that shock dynamics within the gas of a small bubble explains sonoluminescencethe emission of visible radiation in response to spherically symmetric, ultrasonic excitation of a gas bubble in a liquid. As the bubble radius oscillates, shock waves develop from spherical sound waves created inside the gas bubble. As any such shock propagates toward the center, it strengthens
Mixing and Eddie Currents in a Modified Bubble Column Reactor
Anil Kommareddy; Gary Anderson
A modified bubble column reactor is introduced and compared with existing photobioreactors. The modified bubble column reactor uses a porous membrane as the interface between the air and the liquid. The characteristics of the porous membrane are investigated. Gas transfer characteristics of carbon dioxide and oxygen where investigated for the modified bubble column reactor. Bubble size and gas holdup relationships
Slurry bubble column hydrodynamics
NASA Astrophysics Data System (ADS)
Rados, Novica
Slurry bubble column reactors are presently used for a wide range of reactions in both chemical and biochemical industry. The successful design and scale up of slurry bubble column reactors require a complete understanding of multiphase fluid dynamics, i.e. phase mixing, heat and mass transport characteristics. The primary objective of this thesis is to improve presently limited understanding of the gas-liquid-solid slurry bubble column hydrodynamics. The effect of superficial gas velocity (8 to 45 cm/s), pressure (0.1 to 1.0 MPa) and solids loading (20 and 35 wt.%) on the time-averaged solids velocity and turbulent parameter profiles has been studied using Computer Automated Radioactive Particle Tracking (CARPT). To accomplish this, CARPT technique has been significantly improved for the measurements in highly attenuating systems, such as high pressure, high solids loading stainless steel slurry bubble column. At a similar set of operational conditions time-averaged gas and solids holdup profiles have been evaluated using the developed Computed Tomography (CT)/Overall gas holdup procedure. This procedure is based on the combination of the CT scans and the overall gas holdup measurements. The procedure assumes constant solids loading in the radial direction and axially invariant cross-sectionally averaged gas holdup. The obtained experimental holdup, velocity and turbulent parameters data are correlated and compared with the existing low superficial gas velocities and atmospheric pressure CARPT/CT gas-liquid and gas-liquid-solid slurry data. The obtained solids axial velocity radial profiles are compared with the predictions of the one dimensional (1-D) liquid/slurry recirculation phenomenological model. The obtained solids loading axial profiles are compared with the predictions of the Sedimentation and Dispersion Model (SDM). The overall gas holdup values, gas holdup radial profiles, solids loading axial profiles, solids axial velocity radial profiles and solids shear stress radial profiles are correlated using several widely used empirical correlations that are modified and improved to better represent present data.
Influence of slurry concentrations on bubble population and their rise velocities in a three-phase slurry bubble column
H Li; A Prakash
Experiments were performed in airwater and airwaterglass particles systems to study variations in gas holdups, bubble population and their rise velocities. Slurry concentrations up to 40% (v\\/v) and superficial gas velocities up to 0.30 m\\/s were investigated. The measurements were made using fast response pressure transducers and the dynamic gas disengagement (DGD) technique. The gas holdup due to small bubbles
Etiology of gas bubble disease
Bouck, G.R.
Gas bubble disease is a noninfectious, physically induced process caused by uncompensated hyperbaric pressure of total dissolved gases. When pressure compensation is inadequate, dissolved gases may form emboli (in blood) and emphysema (in tissues). The resulting abnormal physical presence of gases can block blood vessels (hemostasis) or tear tissues, and may result in death. Population mortality is generally skewed, in that the median time to death occurs well before the average time to death. Judged from mortality curves, three stages occur in gas bubble disease: (1) a period of gas pressure equilibrium, nonlethal cavitation, and increasing morbidity; (2) a period of rapid and heavy mortality; and (3) a period of protracted survival, despite lesions, and dysfunction that eventually terminates in total mortality. Safe limits for gas supersaturation depend on species tolerance and on factors that differ among hatcheries and rivers, between continuous and intermittent exposures, and across ranges of temperature and salinity.
Simple Microwave Method for Detecting Water Holdup
Iqbal, Sheikh Sharif
Simple Microwave Method for Detecting Water Holdup Sheikh S. I., Alqurashi K. Y., Ragheb H for detecting very small water holdup () transmission measurements are also used to detect sand, water and gas levels within multiphase flow
Hydrodynamic Solutions for a Sonoluminescing Gas Bubble
Ho-Young Kwak; Jung Hee Na
Analytic solutions for a sonoluminescing gas bubble have been obtained, which provide density, pressure, and temperature distributions for the gas inside a bubble oscillating under an ultrasonic field. The solutions show that sonoluminescence occurs due to the increase and subsequent decrease in bubble wall acceleration which induces a thermal spike. It also turns out that the number of electrons ionized,
Shock Pulse from a Sonoluminescing Gas Bubble
NASA Astrophysics Data System (ADS)
Lee, Yoon-Pyo; Karng, Sarng; Jeon, Jin-Seok; Kwak, Ho-Young
The shock pulse emanating from a sonoluminescing gas bubble was calculated by using the analytical solutions of the conservation equations for the gas inside the bubble and the Kirkwood-Bethe hypothesis for the outgoing wave. The rise time and the magnitude of the pulse signal are in good agreement with the observed values, which may provide the approximate value of the gas pressure at near the collapse of the sonoluminescing gas bubble.
Analysis of distributions of gas and TiO 2 particles in slurry bubble column using ultrasonic computed tomography
M. B. Utomo; W. Warsito; T. Sakai; S. Uchida
The ultrasonic computed tomography (UCT) as a coupling of the ultrasonic transmission method and the image reconstruction technique based on the iterative filtered back-projection was applied to investigate the cross-sectional distributions of gas and particle holdups in a slurry bubble column. The dispersion system of airwaterTiO2 was used in this study. The loading of the titanium dioxide particle has affected
King Fahd
Summary This review deals with the discussion of various hy drodynamic and heat-transfer characteristics of bubble and slurry bubble columns both for baffled and unbaffled configurations.The hydrodynamic properties include consideration of initial-bubble diameter, bubble growth, bubble size and size distr ibution, bubble velocity, gas-phase holdup, specific gas-liquid interfacial area, mass- transfer coefficients, different fluid- flow regimes, and effects of operating
Effect of particle lyophobicity in slurry bubble columns at elevated pressures
J. van der Schaaf; V. P. Chilekar; J. R. van Ommen; B. F. M. Kuster; J. T. Tinge; J. C. Schouten
The influence of particle lyophobicity on gas hold-up, homogeneous to churn-turbulent regime transition, and gasliquid mass transfer is investigated in a 0.15m diameter slurry bubble column at pressures from 0.1 to 1.3MPa. An air\\/nitrogen mixture is bubbled through 03vol% slurries of activated carbon particles or silica particles suspended in demineralized water or organic oil Isopar M. The gas hold-up and
Hydrodynamics of semibatch slurry bubble columns with polymer solutions
M. G. Gµmez; Z. Alarcµn; E. Parra; S. Siquier; F. Pironti; A. E. SÃez
In this work we perform an experimental study of the hydrodynamics of semibatch slurry bubble columns in which the liquid phase is a solution of a high molecular weight hydrolyzed polyacrylamide. Experiments were conducted in bubble columns with two different diameters (10 and 29 cm.) In gas-liquid operation, the gas holdup decreases as the polymer concentration increases due to the
Gas bubble dynamics in soft materials
J. M. Solano-Altamirano; John D. Malcolm; Saul Goldman
Epstein and Plesset's seminal work on the rate of gas bubble dissolution and growth in a simple liquid is generalized to render it applicable to a gas bubble embedded in a soft elastic medium. Both the underlying diffusion equation and the expression for the gas bubble pressure were modified to allow for the non-zero shear modulus of the elastic medium. The extension of the diffusion equation results in a trivial shift (by an additive constant) in the value of the diffusion coefficient, and does not change the form of the rate equations. But the use of a Generalized Young-Laplace equation for the bubble pressure resulted in significant differences on the dynamics of bubble dissolution and growth, relative to a simple liquid medium. Depending on whether the salient parameters (solute concentration, initial bubble radius, surface tension, and shear modulus) lead to bubble growth or dissolution, the effect of allowing for a non-zero shear modulus in the Generalized Young-Laplace equation is to speed up the rate of bubble growth, or to reduce the rate of bubble dissolution, respectively. The relation to previous work on visco-elastic materials is discussed, as is the connection of this work to the problem of Decompression Sickness (specifically, "the bends"). Examples of tissues to which our expressions can be applied are provided. Also, a new phenomenon is predicted whereby, for some parameter values, a bubble can be metastable and persist for long times, or it may grow, when embedded in a homogeneous under-saturated soft elastic medium.
Gas bubble dynamics in soft materials.
Solano-Altamirano, J M; Malcolm, John D; Goldman, Saul
Epstein and Plesset's seminal work on the rate of gas bubble dissolution and growth in a simple liquid is generalized to render it applicable to a gas bubble embedded in a soft elastic solid. Both the underlying diffusion equation and the expression for the gas bubble pressure were modified to allow for the non-zero shear modulus of the medium. The extension of the diffusion equation results in a trivial shift (by an additive constant) in the value of the diffusion coefficient, and does not change the form of the rate equations. But the use of a generalized Young-Laplace equation for the bubble pressure resulted in significant differences on the dynamics of bubble dissolution and growth, relative to an inviscid liquid medium. Depending on whether the salient parameters (solute concentration, initial bubble radius, surface tension, and shear modulus) lead to bubble growth or dissolution, the effect of allowing for a non-zero shear modulus in the generalized Young-Laplace equation is to speed up the rate of bubble growth, or to reduce the rate of bubble dissolution, respectively. The relation to previous work on visco-elastic materials is discussed, as is the connection of this work to the problem of Decompression Sickness (specifically, "the bends"). Examples of tissues to which our expressions can be applied are provided. Also, a new phenomenon is predicted whereby, for some parameter values, a bubble can be metastable and persist for long times, or it may grow, when embedded in a homogeneous under-saturated soft elastic medium. PMID:25382720
Dynamics of gas bubbles in monolayers
NASA Astrophysics Data System (ADS)
Berge, Bruno; Simon, Adam J.; Libchaber, Albert
We present a study of the temporal evolution of a two-dimensional bubble pattern in the liquid-gas coexistence region of monolayers. Using fluorescence microscopy of pentadecanoic acid or dipalmitoyl phosphotidylcholine on the surface of water, we study the coarsening of the pattern for several days. Two different regimes appear, depending on the percentage of gas phase observed on the surface. At high gas coverage (~75%), we observe ``polygonal'' gas bubbles separated by thin liquid lines like a two-dimensional soap froth. We confirm the results of Glazier and co-workers [J. A. Glazier, S. P. Gross, and J. Stavans, Phys. Rev. A 36, 306 (1987); J. Stavans and J. A. Glazier, Phys. Rev. Lett. 62, 1318 (1989)] on the nature of the asymptotic scaling states, but find a growth exponent ?~=1.0 for the time evolution of the mean area. At intermediate gas coverage (~50%), we observe weakly interacting ``circular'' gas bubbles, which grow at a slower rate with an exponent ?~=0.6. This state does not reach a scaling regime: The probability distribution for bubble areas broadens continuously and develops a power law at late-stage. The pattern itself evolves toward a critical object. Also, secondary nucleation of tiny liquid droplets in the gas bubbles is observed. The relevance of long-range dipolar interactions is discussed.
Liquid jet pumped by rising gas bubbles
NASA Technical Reports Server (NTRS)
Hussain, N. A.; Siegel, R.
From observations of a stream of gas bubbles rising through a liquid, a two-phase mathematical model is proposed for calculating the induced turbulent vertical liquid flow. The bubbles provide a large buoyancy force and the associated drag on the liquid moves the liquid upward. The liquid pumped upward consists of the bubble wakes and the liquid brought into the jet region by turbulent entrainment. The expansion of the gas bubbles as they arise through the liquid is taken into account. The continuity and momentum equations are solved numerically for an axisymmetric air jet submerged in water. Water pumping rates are obtained as a function of air flow rate and depth of submergence. Comparisons are made with limited experimental information in the literature.
Fluid inclusions with gas bubbles as geothermometers
C. W. Correns; Geol Rundsch
Two types of fluid inclusions can be distinguished. The first is based on the assumption of Sorby (1858) that a homogeneous phase, such as water, salt solution, or CO2, is entrapped, meaning that the bubbles result from the gas of the enclosed fluid. The second type includes foreign gas entrapped with the fluid. \\
Hydrodynamics and local heat transfer measurements in a bubble column with suspension of yeast
A Prakash; A Margaritis; H Li; M. A Bergougnou
Hydrodynamics and heat transfer were investigated in a 0.28m diameter slurry bubble column for airwateryeast cells system. Yeast cells of about 8?m diameter were used and the effects of gas velocity and yeast concentrations were studied. Gas holdups exhibited a maximum value around a gas superficial velocity of 0.10m\\/s when foam height was included. Without the foam layer, gas holdups
Heat transfer and bubble dynamics in bubble and slurry bubble columns with internals for Fischer-Tropsch synthesis of clean alternative fuels and chemicals
NASA Astrophysics Data System (ADS)
Kagumba, Moses Odongo O.
Synthesis gas, a mixture of CO and H2 obtained from coal, natural gas and biomass are increasingly becoming reliable sources of clean synthetic fuels and chemicals and via Fischer-Tropsch (F-T) synthesis process. Slurry bubble column reactor is the reactor of choice for the commercialization of the F-T synthesis. Even though the slurry bubble column reactors and contactors are simple in structures, their design, scale-up, operation, and performance prediction are still challenging and not well understood due to complex interaction of phases. All the studies of heat transfer have been performed without simultaneously investigating the bubble dynamics adjacent to the heat transfer surfaces, particularly in slurry with dense internals. This dissertation focuses on enhancing the understanding of the role of local and overall gas holdup, bubble passage frequency, bubble sizes and bubble velocity on the heat transfer characteristics by means of a hybrid measurement technique comprising an advanced four-point optical probe and a fast response heat transfer probe used simultaneously, in the presence and absence of dense internals. It also seeks to advance a mechanistic approach for estimating the needed parameters for predicting the heat transfer rate in two phase and three phase systems. The results obtained suggest that the smaller diameter internals gives higher heat transfer coefficient, higher local and overall gas holdup, bubble passage frequency and specific interfacial area but smaller bubble sizes and lower axial bubble velocities. The presence of dense internals enhances the heat transfer coefficient in both the large and smaller columns, while increased column diameter increases the heat transfer coefficient, axial bubble velocity, local and overall gas holdup, bubble chord lengths and specific interfacial area. Addition of solids (glass beads) leads to increased bubble chord lengths and increase in axial bubble velocity, but a decrease in local and overall gas holdup, a decrease in bubble passage frequency and decrease in the heat transfer coefficient. Further, a mechanistic assessment of the dependence of the heat transfer coefficient on the bubble dynamics shows that the contact time needed in the heat transfer coefficient estimation is indeed a function of the bubble passage frequency and local gas holdup. Hence the variation of the heat transfer coefficient with contact time is via bubble passage frequency and local gas phase holdup, which are related with sizes and velocity.
Hydrodynamic study in a slurry-bubble-column reactor
Y. Soong; F. W. Harke; I. K. Gamwo; R. R. Schehl; M. F. Zarochak
Local gas holdup, bubble diameter and bubble rise velocity in the nitrogen\\/Drakeol-10 oil system were measured at both laboratory (ambient temperature and pressure) and industrially relevant (high temperature and pressure) conditions using a dual conductivity probe in a slurry-bubble-column reactor. It was found that a constant superficial velocity, the Sauter mean bubble diameter decreases with increasing pressure and temperature. The
Inert gas accumulation in sonoluminescing bubbles
Detlef Lohse; Sascha Hilgenfeldt
In this paper we elaborate on the idea [Lohse et al., Phys. Rev. Lett. 78, 1359-1362 (1997)] that (single) sonoluminescing air bubbles rectify argon. The reason for the rectification is that nitrogen and oxygen dissociate and their reaction products dissolve in water. We give further experimental and theoretical evidence and extend the theory to other gas mixtures. We show that
Experimental setup for the investigation of bubble mediated gas exchange
Jaehne, Bernd
Experimental setup for the investigation of bubble mediated gas exchange Wolfgang firstname.lastname@example.com Abstract. An experimental setup for the measurement of the contribution of air bubbles to gas exchange spectroscopy. The effect of the tracer solubility on the bubble- mediated gas exchange is demonstrated. Key
Gas disengagement technique in a slurry bubble column operated in the coalesced bubble regime
D. J. Lee; X. Luo; L.-S. Fan
The gas disengagement technique is discussed in detail and is applied in a two-dimensional bubble column and slurry bubble column to obtain the bubble size distribution. Flow characteristics including velocities of each phase and dispersed phase size distribution during the gas disengagement process are obtained by using an advanced image analysis tool including a particle image velocimetry technique. It is
A bubble-based microfluidic gas sensor for gas chromatographs.
Bulbul, Ashrafuzzaman; Kim, Hanseup
We report a new proof-of-concept bubble-based gas sensor for a gas chromatography system, which utilizes the unique relationship between the diameters of the produced bubbles with the gas types and mixture ratios as a sensing element. The bubble-based gas sensor consists of gas and liquid channels as well as a nozzle to produce gas bubbles through a micro-structure. It utilizes custom-developed software and an optical camera to statistically analyze the diameters of the produced bubbles in flow. The fabricated gas sensor showed that five types of gases (CO2, He, H2, N2, and CH4) produced (1) unique volumes of 0.44, 0.74, 1.03, 1.28, and 1.42 nL (0%, 68%, 134%, 191%, and 223% higher than that of CO2) and (2) characteristic linear expansion coefficients (slope) of 1.38, 2.93, 3.45, 5.06, and 5.44 nL/(kPa (?L s(-1))(-1)). The gas sensor also demonstrated that (3) different gas mixture ratios of CO2?:?N2 (100?:?0, 80?:?20, 50?:?50, 20?:?80 and 0?:?100) generated characteristic bubble diameters of 48.95, 77.99, 71.00, 78.53 and 99.50 ?m, resulting in a linear coefficient of 10.26 ?m (?L s(-1))(-1). It (4) successfully identified an injection (0.01 ?L) of pentane (C5) into a continuous carrier gas stream of helium (He) by monitoring bubble diameters and creating a chromatogram and demonstrated (5) the output stability within only 5.60% variation in 67 tests over a month. PMID:25350655
Enhancement of Oxygen Mass Transfer and Gas Holdup Using Palm Oil in Stirred Tank Bioreactors with Xanthan Solutions as Simulated Viscous Fermentation Broths
Mohd Sauid, Suhaila; Huey Ling, Tan; Veluri, Murthy V. P. S.
Volumetric mass transfer coefficient (kLa) is an important parameter in bioreactors handling viscous fermentations such as xanthan gum production, as it affects the reactor performance and productivity. Published literatures showed that adding an organic phase such as hydrocarbons or vegetable oil could increase the kLa. The present study opted for palm oil as the organic phase as it is plentiful in Malaysia. Experiments were carried out to study the effect of viscosity, gas holdup, and kLa on the xanthan solution with different palm oil fractions by varying the agitation rate and aeration rate in a 5?L bench-top bioreactor fitted with twin Rushton turbines. Results showed that 10% (v/v) of palm oil raised the kLa of xanthan solution by 1.5 to 3 folds with the highest kLa value of 84.44?h?1. It was also found that palm oil increased the gas holdup and viscosity of the xanthan solution. The kLa values obtained as a function of power input, superficial gas velocity, and palm oil fraction were validated by two different empirical equations. Similarly, the gas holdup obtained as a function of power input and superficial gas velocity was validated by another empirical equation. All correlations were found to fit well with higher determination coefficients. PMID:24350269
Suppression of cavitation inception by gas bubble injection: a numerical study focusing on bubble-bubble interaction.
Ida, Masato; Naoe, Takashi; Futakawa, Masatoshi
The dynamic behavior of cavitation and gas bubbles under negative pressure has been studied numerically to evaluate the effect of gas bubble injection into a liquid on the suppression of cavitation inception. In our previous studies, it was demonstrated by direct observation that cavitation occurs in liquid mercury when mechanical impacts are imposed, and this will cause cavitation damage in spallation neutron sources, in which liquid mercury is bombarded by a high-power proton beam. In the present paper, we describe numerical investigations of the dynamics of cavitation bubbles in liquid mercury using a multibubble model that takes into account the interaction of a cavitation bubble with preexisting gas bubbles through bubble-radiated pressure waves. The numerical results suggest that, if the mercury includes gas bubbles whose equilibrium radius is much larger than that of the cavitation bubble, the explosive expansion of the cavitation bubble (i.e., cavitation inception) is suppressed by the positive-pressure wave radiated by the injected bubbles, which decreases the magnitude of the negative pressure in the mercury. PMID:17995108
Rising and descending bubble size distributions in gasliquid and gasliquidsolid slurry bubble column reactor
Li-juan Zhang; Tao Li; Wei-yong Ying; Ding-ye Fang
Dual-tip conductivity probe is used to determine distributions of rising and descending bubble size in gasliquid and gasliquidsolid bubble column. The column is 100mm in internal diameter and 1500mm in height. The solid particles used are glass beads with average diameter of 17.82?m representing typical particle size for catalytic slurry reactors. Bubbles are categorized to two size classes, small bubbles
Hydrodynamic measurements in a slurry bubble column using ultrasonic techniques
V. Stolojanu; A. Prakash
Ultrasonic techniques were used to measure concentrations of solids and bubbles concentrations in two- and three-phase systems. The measurements have been made over a wide range of solid concentrations and gas holdups to characterize variations in ultrasonic signals in different regions. The solid phase used is 35 ?m glass particles while compressed air and tap water constitute the gas and
This procedure describes the elements of the Safeguards Measurements (SM) holdup program. This procedure supplies job aids for evaluating non-routine holdup measurement locations. This procedure is intended to allow operational freedom to evaluate and measure holdup based on the supplied information. This procedure describes suggested measurement techniques which can be employed independently or in combination. Safety requirements and prerequisites are expected to be followed completely.
Dissolved gas quantification and bubble formation in liquid chemical dispense
NASA Astrophysics Data System (ADS)
Tom, Glenn; Liu, Wei
Gas dissolved in liquids such as photoresist comes out of solution as bubbles after the liquid experiences a pressure drop in a dispense train and may cause on-wafer defects. Reservoirs in the dispense train can assist in removing bubbles but are incapable of effectively removing dissolved gas. This study demonstrates the importance of maintaining the amount of dissolved gas in a liquid below a critical value to reduce bubbles generated after a pressure drop in the dispense train occurs. The methodology used to quantify dissolved gas during liquid dispense cycle using gas chromatography is discussed. The amount of dissolved gas is correlated to the amount of bubbles downstream of a pressure drop. This study also analyzes sources of bubbles in the dispense train and techniques to mediate the sources.
Standards for holdup measurement
Zucker, M.S.
Holdup measurement, needed for material balance, depend intensively on standards and on interpretation of the calibration procedure. More than other measurements, the calibration procedure using the standard becomes part of the standard. Standards practical for field use and calibration techniques have been developed. While accuracy in holdup measurements is comparatively poor, avoidance of bias is a necessary goal.
Active microfluidic mixer and gas bubble filter driven by thermal bubble micropump
Jr-Hung Tsai; Liwei Lin
A microfluidic mixer with a gas bubble filter activated by a thermal bubble actuated nozzle-diffuser micropump is successfully demonstrated. The oscillatory flow generated by the micropump can induce wavy interface to increase the contact area of mixing fluids to accelerate the mixing process. The microfluidic mixing channels are 200?m wide, 50?m deep and the speed of the mixing liquids are
Gas Bubble Formation in Stagnant and Flowing Mercury
Wendel, Mark W [ORNL] [ORNL; Abdou, Ashraf A [ORNL] [ORNL; Riemer, Bernie [ORNL] [ORNL; Felde, David K [ORNL] [ORNL
Investigations in the area of two-phase flow at the Oak Ridge National Laboratory's (ORNL) Spallation Neutron Source (SNS) facility are progressing. It is expected that the target vessel lifetime could be extended by introducing gas into the liquid mercury target. As part of an effort to validate the two-phase computational fluid dynamics (CFD) model, simulations and experiments of gas injection in stagnant and flowing mercury have been completed. The volume of fluid (VOF) method as implemented in ANSYS-CFX, was used to simulate the unsteady two-phase flow of gas injection into stagnant mercury. Bubbles produced at the upwards-oriented vertical gas injector were measured with proton radiography at the Los Alamos Neutron Science Center. The comparison of the CFD results to the radiographic images shows good agreement for bubble sizes and shapes at various stages of the bubble growth, detachment, and gravitational rise. Although several gas flows were measured, this paper focuses on the case with a gas flow rate of 8 cc/min through the 100-micron-diameter injector needle. The acoustic waves emitted due to the detachment of the bubble and during subsequent bubble oscillations were recorded with a microphone, providing a precise measurement of the bubble sizes. As the mercury flow rate increases, the drag force causes earlier bubble detachment and therefore smaller bubbles.
Bubble formation at a gas-evolving microelectrode.
FernÃndez, Damaris; Maurer, Paco; Martine, Milena; Coey, J M D; M—bius, Matthias E
The electrolytic production of gas bubbles involves three steps--nucleation, growth, and detachment. Here the growth of hydrogen bubbles and their detachment from a platinum microelectrode of diameter 125 ?m are studied using high-speed photography and overpotential frequency spectrum (noise) analysis. The periodic release of large <800 ?m bubbles--gas oscillator behavior--was often observed, with a corresponding periodic oscillation of the overpotential which is reflected as a main peak and a series of harmonics in the power spectral density. The release frequency is inversely correlated with the bubble size and hydrogen production rate. When the coalescence of bubbles at the electrode surface is inhibited, either chemically with a surfactant or ethylene glycol or hydrodynamically by magnetically induced convection, swarms of small ?50 ?m bubbles are released in an aperiodic stream. The abrupt transition from periodic to aperiodic release occurs when the surface tension falls below 70 mN m(-1). Hydrogen bubble growth is also studied on a transparent platinum thin-film electrode, where the bubble coalescence can be observed directly. It leaves sessile droplets of electrolyte within the footprint of the growing bubble, showing that the growth involves scavenging smaller bubbles from solution due to hydrogen generated directly at the electrode. A possible role of nanobubbles in the lift-off process is discussed. PMID:24694174
Determination and evaluation of gas holdup time with the quadratic equation model and comparison with nonlinear equation models for isothermal gas chromatography
Wu, Liejun; Chen, Maoxue; Chen, Yongli; Li, Qing X.
Gas holdup time (tM) is a basic parameter in isothermal gas chromatography (GC). Determination and evaluation of tM and retention behaviors of n-alkanes under isothermal GC conditions have been extensively studied since the 1950s, but still remains unresolved. The difference equation (DE) model [J. Chromatogr. A 1260:215223] reveals retention behaviors of n-alkanes excluding tM, while the quadratic equation (QE) model [J. Chromatogr. A 1260:224231] including tM is suitable for applications. In the present study, tM values were calculated with the QE model, which is referred to as tMT, evaluated and compared with other three typical nonlinear models. The QE model gives an accurate estimation of tM in isothermal GC. The tMT values are highly accurate, stable, and easy to calculate and use. There is only one tMT value at each GC condition. The proper classification of tM values can clarify their disagreement and facilitate GC retention data standardization for which tMT values are promising reference tM values. PMID:23726077
On the motion of gas bubbles in homogeneous isotropic turbulence
P. D. M. Spelt; A. Biesheuvel
This paper is concerned with the motion of small gas bubbles, equivalent diameter about 1.0 mm, in isotropic turbulent flows. Data on the mean velocity of rise and the dispersion of the bubbles have been obtained numerically by simulating the turbulence as a sum of Fourier modes with random phases and amplitudes determined by the Kraichnan and the von KÃrmÃn
1. Introduction Slag foaming consists of introducing gas bubbles into
Pilon, Laurent
1. Introduction Slag foaming consists of introducing gas bubbles into molten metal and slag by either bubble injection or by chemical reaction. In the early days of steel manufacturing, slag foaming- dure. Therefore, studies were limited to ways of reducing or eliminating slag foaming during iron
Effect of noble gas doping in single-bubble sonoluminescence
Hiller, R.; Weninger, K.; Putterman, S.J.; Barber, B.P. [Univ. of California, Los Angeles, CA (United States)
The trillionfold concentration of sound energy by a trapped gas bubble, so as to emit picosecond flashes of ultraviolet light, is found to be extremely sensitive to doping with a noble gas. Increasing the noble gas content of a nitrogen bubble to about 1% dramatically stabilizes the bubble motion and increases the light emission by over an order of magnitude to a value that exceeds the sonoluminescence of either gas alone. The spectrum also strongly depends on the nature of the gas inside the bubble: Xenon yields a spectral peak at about 300 nanometers, whereas the helium spectrum is so strongly ultraviolet that its peak is obscured by the cutoff of water. 18 refs., 5 figs.
Heat transfer investigations in a slurry bubble column
S. C. Saxena; N. S. Rao; R. Vadivel; S. Shrivastav; A. C. Saxena; B. B. Patel; P. R. Thimmapuram; M. Y. Kagzi; I. A. Khan; A. K. Verma
Slurry bubble columns, for use in Fisher-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven- or thirty-seven tubes. The experiments were conducted
Heat transfer investigations in a slurry bubble column
S. C. Saxena; N. S. Rao; R. Vadivel; S. Shrivastav; A. C. Saxena; B. B. Patel; P. R. Thimmapuram; M. Y. Kagzi; I. A. Khan; A. K. Verma
Slurry bubble columns, for use in Fischer-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven-, or thirty-seven tubes. the experiments were conducted
Dysbaric gas bubble disease in dogs. IV. Acclimatization to diving
Kunkle, T.D.; Morita, A.; Beckman, E.L.
Acclimatization to diving was documented to occur in dogs. An increase in the number of repetitive dives which could be tolerated, as well as a decrease in the total number of pulmonary artery venous gas emboli resulting from individual dives were observed. The results from the experimental subject ''Jason'' indicate that acclimatization involves a reduction in the number of bubbles, and not an increase in the ability of the body to tolerate bubbles. Acclimatization is principally a physical rather than a physiological event. Bubbles forming in vivo must grow from nuclei of some sort. If these nuclei are stable, discrete structure that are destroyed when they grow into gross bubbles, then repetitive diving might markedly reduce by attrition the number of such bubble micronuclei. This would result in fewer bubbles being formed during subsequent dives, thus leading to the observed acclimatization effect. 7 refs., 3 figs., 4 tabs.
Dust and Gas Emission from MIR Bubble N56
NASA Astrophysics Data System (ADS)
Devine, Kathryn E.; Watson, Christer; Candelaria, Tierra; Rodriguez, Paula; Low, Cassiemarie; Pickett, Joseph
Mid-infrared (MIR) bubbles, identified in galactic surveys, have been extensively studied with the aim of understanding both their structure and influence on the surrounding interstellar medium. Studies of MIR bubbles aim to explore the relationship between bubble expansion and subsequent star formation. We present observations toward bubble N56 using the Herschel Space Telescope and Green Bank Telescope (GBT). The Herschel continuum observations indicate that N56 may be forming within a high mass-scale environment. The GBT NH3(1,1) and NH3(2,2) spectral line observations indicate evidence of line broadening and velocity changes coincident with the MIR-identified bubble rim. The temperature, density, and kinematics of the gas along the bubble rim are presented. We also discuss the relationship between the kinematics, physical properties, and star formation in N56.
Bubble coalescence dynamics and supersaturation in electrolytic gas evolution
Stover, R.L. [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering]|[Lawrence Berkeley National Lab., CA (United States). Energy and Environment Div.
The apparatus and procedures developed in this research permit the observation of electrolytic bubble coalescence, which heretofore has not been possible. The influence of bubble size, electrolyte viscosity, surface tension, gas type, and pH on bubble coalescence was examined. The Navier-Stokes equations with free surface boundary conditions were solved numerically for the full range of experimental variables that were examined. Based on this study, the following mechanism for bubble coalescence emerges: when two gas bubbles coalesce, the surface energy decreases as the curvature and surface area of the resultant bubble decrease, and the energy is imparted into the surrounding liquid. The initial motion is driven by the surface tension and slowed by the inertia and viscosity of the surrounding fluid. The initial velocity of the interface is approximately proportional to the square root of the surface tension and inversely proportional to the square root of the bubble radius. Fluid inertia sustains the oblate/prolate oscillations of the resultant bubble. The period of the oscillations varies with the bubble radius raised to the 3/2 power and inversely with the square root of the surface tension. Viscous resistance dampens the oscillations at a rate proportional to the viscosity and inversely proportional to the square of the bubble radius. The numerical simulations were consistent with most of the experimental results. The differences between the computed and measured saddle point decelerations and periods suggest that the surface tension in the experiments may have changed during each run. By adjusting the surface tension in the simulation, a good fit was obtained for the 150-{micro}m diameter bubbles. The simulations fit the experiments on larger bubbles with very little adjustment of surface tension. A more focused analysis should be done to elucidate the phenomena that occur in the receding liquid film immediately following rupture.
Modelling of gas evolving electrolysis cells. I. The gas voidage problem
G. Kreysa; M. Kuhn
A critical review of experimental gas voidage data for gasliquid mixtures available in the literature yields the result that these data cannot be explained by known theories of the gas hold-up. Based on the empirical experience that bubble coalescence is hindered in electrolyte solutions, new equations are derived for the calculation of the gas voidage as a function of the
Production of Gas Bubbles in Reduced Gravity Environments
NASA Technical Reports Server (NTRS)
Oguz, Hasan N.; Takagi, Shu; Misawa, Masaki
In a wide variety of applications such as waste water treatment, biological reactors, gas-liquid reactors, blood oxygenation, purification of liquids, etc., it is necessary to produce small bubbles in liquids. Since gravity plays an essential role in currently available techniques, the adaptation of these applications to space requires the development of new tools. Under normal gravity, bubbles are typically generated by forcing gas through an orifice in a liquid. When a growing bubble becomes large enough, the buoyancy dominates the surface tension force causing it to detach from the orifice. In space, the process is quite different and the bubble may remain attached to the orifice indefinitely. The most practical approach to simulating gravity seems to be imposing an ambient flow to force bubbles out of the orifice. In this paper, we are interested in the effect of an imposed flow in 0 and 1 g. Specifically, we investigate the process of bubble formation subject to a parallel and a cross flow. In the case of parallel flow, we have a hypodermic needle in a tube from which bubbles can be produced. On the other hand, the cross flow condition is established by forcing bubbles through an orifice on a wall in a shear flow. The first series of experiments have been performed under normal gravity conditions and the working fluid was water. A high quality microgravity facility has been used for the second type and silicone oil is used as the host liquid.
Proton Radiography Experiment to Visualize Gas Bubbles in Mercury
Riemer, Bernie [ORNL; Felde, David K [ORNL; Wendel, Mark W [ORNL; Mariam, Fesseha G [Los Alamos National Laboratory (LANL); Merrill, Frank E [ORNL
An experiment to visualize small gas bubbles injected into mercury flowing in a test loop using proton radiography was conducted at the Los Alamos Neutron Science Center (LANSCE) in December 2006. Radiograph images of bubbles were obtained through two mercury thicknesses: 22 mm and 6 mm. Two jet bubblers and two needle bubblers were operated individually over a range of mercury flow speeds (0 - 1 m/s) and gas injection rates (0.1 - 500 sccm). Helium was most commonly used but Argon and Xenon were injected for limited test conditions. The smallest discernable bubbles were about 0.24 mm in diameter. Resolution was limited by image contrast which was notably improved with 6 mm of mercury thickness. Analysis of the radiograph images from jet bubbler conditions provided data on bubble size distribution and total bubble void fraction. In a few cases radiographs captured a large fraction of the injected gas, but generally 20 to 90% of injected gas was not captured in the images. In all more than 400 radiographs were made during the experiment in addition to several movies. Sound recordings of needle bubbler operation were also made and used to quantify bubble formation rate and size; these results are compared to theoretical predictions. This paper describes the experiment goals, scope and equipment; key results are presented and discussed.
Hydrodynamics of the three-phase slurry Fischer-Tropsch bubble column reactors
Bukur, D.B.; Daly, J.G.; Patel, S.A.
This report describes results of a study on hydrodynamics of three-phase bubble columns for Fischer-Tropsch synthesis. Experiments were conducted in two stainless bubble columns of 0.05 m and 0.21 m in diameter and 3 m tall, at 265{degrees}C and atmospheric pressure using nitrogen gas and two types of liquid medium (hydrotreated reactor wax designated FT-300, and raw reactor wax from fixed bed rectors at SASOL). The effects of solids types (iron oxide and silica), concentration (0--30 wt %), size (0--5 {mu}m and 20--44 {mu}m), slurry (liquid) velocity (up to 0.02 m/s) on the gas holdup and axial solids concentration profiles, were investigated. Phase volume fractions were determined using conventional (differential pressure measurements together with determination of slurry concentration along the column) and novel (dual energy nuclear density gauge) experimental techniques. Bubble size distribution and the Sauter mean bubble diameter were obtained using the dynamic gas disengagement (DGD) method. Flow regime transitions in both columns were determined using statistical analysis of both pressure and density fluctuations. Correlations for prediction of gas holdups and axial solids dispersion coefficient have been developed from experimental data obtained in this study. Data needed for calculation of the gas-liquid interfacial area (average gas holdup and Sauter mean bubble diameter) have been presented and can be used to estimate the mass transfer rate in slurry bubble column reactors. 105 refs., 19 figs., 38 tabs.
Gas Bubble Reabsorption in Chinook Salmon: Pressurization Effects
Ralph Elston; John Colt; Scott Abernethy; William Maslen
Gas bubble disease (GBD) can cause substantial morbidity and mortality of salmonids and other fishes residing in gas supersaturated water. The monitoring program for examining the prevalence of GBD in the Columbia and Snake rivers is only based on fish collected in the smolt bypass systems; fish that pass through the turbines, nagivation locks, adult fish ladders, or spillways are
Progression and Severity of Gas Bubble Trauma in Juvenile Salmonids
Matthew G. Mesa; Lisa K. Weiland; Alec G. Maule
We conducted laboratory experiments to assess the progression and to quantify the severity of signs of gas bubble trauma (GBT) in juvenile chinook salmon Oncorhynchus tshawytscha and steelhead Oncorhynchus mykiss exposed to different levels of total dissolved gas (TDG), and we attempted to relate these signs to the likelihood of mortality. When fish were exposed to 110% TDG for up
Gas permeability in polymer- and surfactant-stabilized bubble films.
Andreatta, GaŠlle; Lee, Lay-Theng; Lee, Fuk Kay; Benattar, Jean-Jacques
The gas permeabilities of thin liquid films stabilized by poly(N-isopropylacrylamide) (PNIPAM) and PNIPAM-SDS (sodium dodecyl sulfate) mixtures are studied using the "diminishing bubble" method. The method consists of forming a microbubble on the surface of the polymer solution and measuring the shrinking rates of the bubble and the bubble film as the gas diffuses from the interior to the exterior of the bubble. PNIPAM-stabilized films exhibit variable thicknesses and homogeneities. Interestingly, despite these variable features, the gas permeability of the film is determined principally by the structure of the adsorbed polymer layer that provides an efficient gas barrier with a value of gas permeability coefficient that is comparable to that of an SDS Newton black film. In the presence of SDS, both the film homogeneity and the gas permeability coefficient increase. These changes are related to interactions of PNIPAM with SDS in the solution and at the interface, where coadsorption of the two species forms mixed layers that are stable but that are more porous to gas transfer. The mixed PNIPAM-SDS layers, studied previously for a single water-air interface by neutron reflectivity, are further characterized here in a vertical free-draining film using X-ray reflectivity. PMID:17004816
Effect of dense heat exchanging internals on the hydrodynamics of bubble column reactors using non-invasive measurement techniques
NASA Astrophysics Data System (ADS)
Al Mesfer, Mohammed Khloofh
Given their efficiency and capital cost reduction, bubble/slurry bubble column reactors are the reactors of choice for Fischer-Tropsch (FT) synthesis, offering clean alternative fuels and chemicals. FT synthesis is an exothermic process that requires many heat exchanging tubes in order to remove heat efficiently and maintain the desired temperature and isothermal operating condition. The impact of the heat exchanging tubes (internals) on the hydrodynamics is not fully understood. Reliably designing and scaling up bubble column reactors requires proper understanding of hydrodynamics, as well as heat and mass transfer parameters. The main objective of this work is to advance the understanding of the effect of internals (25% covered cross-sectional area to meet FT needs) on hydrodynamics (gas holdup distribution, 3D liquid velocity, Reynolds stresses, turbulent kinetic energy, eddy diffusivity, etc.) in bubble columns. Single-source gamma-ray Computed Tomography (CT) and Radioactive Particle Tracking (RPT) were used for the first time to study the effect of dense internals and gas velocity on the phase holdup distribution and radial profiles, liquid velocity field and turbulent parameter profiles. The main findings obtained for the first time in this study can be summarized as follows: The presence of internals at a given superficial gas velocity causes: An increase in gas holdup and the axial centerline liquid velocity. A sharp decrease in turbulence parmeters. The increase in superficial gas velocity in the presence of internals causes: An increase in gas holdup, axial centerline liquid velocity and turbulent parameters.
Transient Flow Dynamics in Optical Micro Well Involving Gas Bubbles
NASA Technical Reports Server (NTRS)
Johnson, B.; Chen, C. P.; Jenkins, A.; Spearing, S.; Monaco, L. A.; Steele, A.; Flores, G.
The Lab-On-a-Chip Application Development (LOCAD) team at NASA s Marshall Space Flight Center is utilizing Lab-On-a-Chip to support technology development specifically for Space Exploration. In this paper, we investigate the transient two-phase flow patterns in an optic well configuration with an entrapped bubble through numerical simulation. Specifically, the filling processes of a liquid inside an expanded chamber that has bubbles entrapped. Due to the back flow created by channel expansion, the entrapped bubbles tend to stay stationary at the immediate downstream of the expansion. Due to the huge difference between the gas and liquid densities, mass conservation issues associated with numerical diffusion need to be specially addressed. The results are presented in terms of the movement of the bubble through the optic well. Bubble removal strategies are developed that involve only pressure gradients across the optic well. Results show that for the bubble to be moved through the well, pressure pulsations must be utilized in order to create pressure gradients across the bubble itself.
Spectra of Stable Non-Noble Gas Single Bubble Sonoluminescence
Levinsen, M T; Levinsen, Mogens T.; Dam, Jeppe Seidelin
A commonly accepted view is that stable Single Bubble Sonoluminescence (SBSL) can only be achieved in the presence of a noble gas or hydrogen. In air-seeded bubbles, the content of diatomic gasses is burned off to leave the small amount of argon needed to sustain stable operation. Here we report that long term stable SBSL can be sustained with only nitrogen, oxygen, or nitrogen/oxygen mixtures being present. Compared to that of a stable argon bubble, the emission is much weaker and the spectrum looks much colder. Oscillating states as well as recycling states are also observed. An intriguing saturation effect seems connected with the presence of water vapor in the bubble.
Measurements of Gas Bubble Size Distributions in Flowing Liquid Mercury
Wendel, Mark W [ORNL; Riemer, Bernie [ORNL; Abdou, Ashraf A [ORNL
ABSTRACT Pressure waves created in liquid mercury pulsed spallation targets have been shown to induce cavitation damage on the target container. One way to mitigate such damage would be to absorb the pressure pulse energy into a dispersed population of small bubbles, however, measuring such a population in mercury is difficult since it is opaque and the mercury is involved in a turbulent flow. Ultrasonic measurements have been attempted on these types of flows, but the flow noise can interfere with the measurement, and the results are unverifiable and often unrealistic. Recently, a flow loop was built and operated at Oak Ridge National Labarotory to assess the capability of various bubbler designs to deliver an adequate population of bubbles to mitigate cavitation damage. The invented diagnostic technique involves flowing the mercury with entrained gas bubbles in a steady state through a horizontal piping section with a glass-window observation port located on the top. The mercury flow is then suddenly stopped and the bubbles are allowed to settle on the glass due to buoyancy. Using a bright-field illumination and a high-speed camera, the arriving bubbles are detected and counted, and then the images can be processed to determine the bubble populations. After using this technique to collect data on each bubbler, bubble size distributions were built for the purpose of quantifying bubbler performance, allowing the selection of the best bubbler options. This paper presents the novel procedure, photographic technique, sample visual results and some example bubble size distributions. The best bubbler options were subsequently used in proton beam irradiation tests performed at the Los Alamos National Laboratory. The cavitation damage results from the irradiated test plates in contact with the mercury are available for correlation with the bubble populations. The most effective mitigating population can now be designed into prototypical geometries for implementation into an actual SNS target.
Pillay, K.K.S.; Picard, R.R.
Holdup of special nuclear materials in processing facilities is recognized by facility operators and regulatory agencies as an insidious materials control and accounting problem. However, there have been few serious efforts to address holdup as a materials accounting problem and to accommodate the legitimate concerns of both groups. This paper reviews past efforts and identifies several key elements relevant to resolving the problem in a pragmatic fashion. These key elements relate to the recognition of holdup as a serious materials accounting problem, innovations in holdup monitoring and their limitations, the role of modeling and sampling in holdup estimation, and the potential value of plant-specific materials accountability requirements. Suggestions are offered for developing cost-effective procedures for holdup measurements/estimation, combining available technologies with properly designed sampling plans.
Radiation Characteristics of Glass Containing Gas Bubbles Laurent Pilon*
Pilon, Laurent
Lafayette, Indiana 47907 In many materials processing and manufacturing situations such as steel, aluminum of the continuous phase are small. I. Introduction IN MANY materials processing and manufacturing situations such as steel, aluminum, ceramics, and glass, gas bubbles can form in liquid and solid phases. The presence
Mass and momentum transfer enhancement due to electrogenerated gas bubbles
F. Giron; G. Valentin; M. Lebouche; A. Storck
The effect of electrogenerated gas bubbles with simultaneous bulk liquid flow on the mass and momentum transfer at a wall of an electrolytic cell is experimentally determined. The local mass transfer coefficient and electrolyte shear stress are obtained using two types of microelectrodes imbedded in the channel wall. The influence of the most important parameters (electrolyte velocity, position along the
Holdup measurements under realistic conditions
Sprinkel, J.K. Jr.; Marshall, R.; Russo, P.A.; Siebelist, R. [and others
This paper reviews the documentation of the precision and bias of holdup (residual nuclear material remaining in processing equipment) measurements and presents previously unreported results. Precision and bias results for holdup measurements are reported from training seminars with simulated holdup, which represent the best possible results, and compared to actual plutonium processing facility measurements. Holdup measurements for plutonium and uranium processing plants are also compared to reference values. Recommendations for measuring holdup are provided for highly enriched uranium facilities and for low enriched uranium facilities. The random error component of holdup measurements is less than the systematic error component. The most likely factor in measurement error is incorrect assumptions about the measurement, such as background, measurement geometry, or signal attenuation. Measurement precision on the order of 10% can be achieved with some difficulty. Bias of poor quality holdup measurement can also be improved. However, for most facilities, holdup measurement errors have no significant impact on inventory difference, sigma, or safety (criticality, radiation, or environmental); therefore, it is difficult to justify the allocation of more resources to improving holdup measurements. 25 refs., 10 tabs.
Easy and accurate calculation of programmed temperature gas chromatographic retention times by back-calculation of temperature and hold-up time profiles.
Boswell, Paul G; Carr, Peter W; Cohen, Jerry D; Hegeman, Adrian D
Linear retention indices are commonly used to identify compounds in programmed-temperature gas chromatography (GC), but they are unreliable unless the original experimental conditions used to measure them are stringently reproduced. However, differences in many experimental conditions may be properly taken into account by calculating programmed-temperature retention times of compounds from their measured isothermal retention vs. temperature relationships. We call this approach "retention projection". Until now, retention projection has been impractical because it required very precise, meticulous measurement of the temperature vs. time and hold-up time vs. temperature profiles actually produced by a specific GC instrument to be accurate. Here we present a new, easy-to-use methodology to precisely measure those profiles: we spike a sample with 25 n-alkanes and use their measured, programmed-temperature retention times to precisely back-calculate what the instrument profiles must have been. Then, when we use those back-calculated profiles to project retention times of 63 chemically diverse compounds, we found that the projections are extremely accurate (e.g. to Ý0.9 s in a 40 min ramp). They remained accurate with different temperature programs, GC instruments, inlet pressures, flow rates, and with columns taken from different batches of stationary phase while the accuracy of retention indices became worse the more the experimental conditions were changed from the original ones used to measure them. We also developed new, open-source software (http://www.retentionprediction.org/gc) to demonstrate the system. PMID:23040964
Hot Gas in the Circumstellar Bubble S308
NASA Astrophysics Data System (ADS)
Chu, You-Hua; Guerrero, MartÚn A.; Gruendl, Robert A.; GarcÚa-Segura, Guillermo; Wendker, Heinrich J.
S308 is a circumstellar bubble blown by the WN4 star HD 50896. It is one of the only two single-star bubbles that show detectable diffuse X-ray emission. We have obtained XMM-Newton EPIC observations of the northwest quadrant of S308. The diffuse X-ray emission shows a limb-brightened morphology, with a clear gap extending from the outer edge of the diffuse X-ray emission to the outer rim of the nebular shell. The X-ray spectrum of the diffuse emission is very soft and is well fitted by an optically thin plasma model for an N-enriched plasma at temperatures of ~1.1æ106 K. A hotter gas component may exist but its temperature is not well constrained since it contributes less than 6% of the observed X-ray flux. The total X-ray luminosity of S308, extrapolated from the bright northwest quadrant, is <=(1.2+/-0.5)æ1034 ergs s-1. We have used the observed bubble dynamics and the physical parameters of the hot interior gas of S308, in conjunction with the circumstellar bubble model of GarcÚa-Segura & Mac Low, to demonstrate that the X-ray-emitting gas must be dominated by mixed-in nebular material.
Heat transfer between immiscible liquids enhanced by gas bubbling
NASA Astrophysics Data System (ADS)
Greene, G. A.; Schwarz, C. E.; Klages, J.; Klein, J.
The phenomena of core-concrete interactions impact upon containment integrity of light water reactors (LWR) following postulated complete meltdown of the core by containment pressurization, production of combustible gases, and basemat penetration. Experiments were performed with nonreactor materials to investigate one aspect of this problem, heat transfer between overlying immiscible liquids whose interface is disturbed by a transverse non-condensable gas flux emanating from below. Hydrodynamic studies were performed to test a criterion for onset of entrainment due to bubbling through the interface and subsequent heat transfer studies were performed to assess the effect of bubbling on interfacial heat transfer rates, both with and without bubble induced entrainment. Non entraining interfacial heat transfer data with mercury-water/oil fluid pairs were observed to be bounded from below within a factor of two to three by the Szekeley surface renewal heat transfer model.
Porosity formation and gas bubble retention in laser metal deposition
NASA Astrophysics Data System (ADS)
Ng, G. K. L.; Jarfors, A. E. W.; Bi, G.; Zheng, H. Y.
One of the inherent problems associated with laser metal deposition using gas-assisted powder transfer is the formation of porosity, which can be detrimental to the mechanical properties of the bulk material. In this work, a comprehensive investigation of porosity is carried out using gas atomised Inconel 718 powder. In the analysis, a clear distinction is made between two types of porosity; namely lack of fusion and gas porosity. The results show that the two types of porosity are attributed by different factors. The gas porosity, which is more difficult to eliminate than the lack of fusion, can be as high as 0.7%. The study shows that the gas porosity is dependent on the process parameters and the melt pool dynamics. The flotation of entrapped gas bubbles was analysed, showing that in a stationary melt pool the gas would be retained by Marangoni-driven flow. The overall Marangoni-driven flow of the melt pool is in the order of five times higher than the flotation effect, and this is the reason why the melt pool geometry would tend to dominate the flow direction of the gas bubbles. Through optimisation, the gas porosity can be reduced to 0.037%.
Volumetric mass transfer coefficient in a slurry bubble column operating in the heterogeneous flow regime
C. O. Vandu; K. Koop; R. Krishna
We report the results of an experimental study of the gas holdup, ?G, and volumetric mass transfer coefficient, kLa, in a bubble column slurry reactor of 0.1m diameter operated at ambient temperature and pressure conditions. The superficial gas velocity U was varied in the range 00.4m\\/s, spanning both the homogeneous and churn-turbulent flow regimes. Air was used as the gas
Volumetric mass transfer coefficients in slurry bubble columns operating in the churn-turbulent flow regime
C. O. Vandu; R. Krishna
We report the results of an extensive experimental study of the gas hold-up, ?, and volumetric mass transfer coefficient, kLa, in bubble columns operated at ambient temperature and pressure conditions. The superficial gas velocity U was varied in the range 00.4m\\/s, spanning both the homogeneous and churn-turbulent flow regimes. Air was used as the gas phase in all cases. Three
Modelling of bubble-mediated gas transfer: Fundamental principles and a laboratory test
D. K. Woolf; I. S. Leifer; P. D. Nightingale; T. S. Rhee; P. Bowyer; G. Caulliez; G. de Leeuw; S. E. Larsen; M. Liddicoat; J. Baker; M. O. Andreae
The airwater exchange of gases can be substantially enhanced by wave breaking and specifically by bubble-mediated transfer. A feature of bubble-mediated transfer is the additional pressure on bubbles resulting from the hydrostatic forces on a submerged bubble and from surface tension and curvature. This peculiarity results in asymmetry of bubble-mediated gas transfer and equilibrium supersaturations of dissolved gases in a
Effects of micron-sized particles on hydrodynamics and local heat transfer in a slurry bubble column
H Li; A Prakash; A Margaritis; M. A Bergougnou
Hydrodynamics and heat transfer in an airwaterglass bead system are investigated to study the effects of particle size (1193 ?m) and slurry concentration (up to 40 vol.%). The effect of particle size on gas holdup is only slight over the range of particle size investigated. This can be attributed to differences in rise velocities of different bubble fractions. Small bubble
Modeling biogenic gas bubbles formation and migration in coarse sand
NASA Astrophysics Data System (ADS)
Ye, S.
Shujun Ye Department of Hydrosciences, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China; firstname.lastname@example.com Brent E. Sleep Department of Civil Engineering, University of Toronto, Toronto, ON, M5S 1A4 CANADA; email@example.com Methane gas generation in porous media was investigated in an anaerobic two-dimensional sand-filled cell. Inoculation of the lower portion of the cell with a methanogenic culture and addition of methanol to the bottom of the cell led to biomass growth and formation of a gas phase. The formation, migration, distribution and saturation of gases in the cell were visualized by the charge-coupled device (CCD) camera. Gas generated at the bottom of the cell in the biologically active zone moved upwards in discrete fingers, so that gas phase saturations (gas-filled fraction of void space) in the biologically active zone at the bottom of the cell did not exceed 40-50%, while gas accumulation at the top of the cell produced gas phase saturations as high as 80%. Macroscopic invasion percolation (MIP) at near pore scale[Glass, et al., 2001; Kueper and McWhorter, 1992]was used to model gas bubbles growth in porous media. The nonwetting phase migration pathway can be yielded directly by MIP. MIP was adopted to simulate the expansion, fragmentation, and mobilization of gas clusters in the cell. The production of gas, and gas phash saturations were simulated by a continuum model - compositional simulator (COMPSIM) [Sleep and Sykes, 1993]. So a combination of a continuum model and a MIP model was used to simulate the formation, fragmentation and migration of biogenic gas bubbles. Key words: biogenic gas; two dimensional; porous media; MIP; COMPSIM
CFD simulation of steady state heat transfer in bubble columns
Mahesh T. Dhotre; Vivek S. Vitankar; Jyeshtharaj B. Joshi
A low Reynolds number k? computational fluid dynamics (CFD) model has been used for the description of flow pattern near the wall. An excellent agreement has been shown between the predicted and experimental hold-up and velocity profiles. The CFD model has been extended for the prediction of heat transfer for two-phase gasliquid flows in bubble columns. A comparison has been
Numerical simulation of multiphase flow in bubble column reactors. Influence of bubble coalescence and break-up
E Olmos; C Gentric; Ch Vial; G Wild; N Midoux
Population balance equations have been combined to a classical hydrodynamic Euler\\/Euler simulation to investigate the operation of a cylindrical bubble column. The MUSIG (mutiple-size-group) model implemented in the CFX 4.3 commercial software has been used. Hydrodynamic experimental variables, i.e. local axial liquid velocity and local gas hold-up, have been compared to the corresponding calculated values, showing a quite good agreement,
Warm Pressurant Gas Effects on the Liquid Hydrogen Bubble Point
NASA Technical Reports Server (NTRS)
Hartwig, Jason W.; McQuillen, John B.; Chato, David J.
This paper presents experimental results for the liquid hydrogen bubble point tests using warm pressurant gases conducted at the Cryogenic Components Cell 7 facility at the NASA Glenn Research Center in Cleveland, Ohio. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device. Three fine mesh screen samples (325 x 2300, 450 x 2750, 510 x 3600) were tested in liquid hydrogen using cold and warm noncondensible (gaseous helium) and condensable (gaseous hydrogen) pressurization schemes. Gases were conditioned from 0 to 90 K above the liquid temperature. Results clearly indicate a degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over noncondensible pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.
Dynamic simulation of dispersed gas-liquid two-phase flow using a discrete bubble model
E. Delnoij; F. A. Lammers; J. A. M. Kuipers; W. P. M. van Swaaij
In this paper a detailed hydrodynamic model for gas-liquid two-phase flow will be presented. The model is based on a mixed Eulerian-Lagrangian approach and describes the time-dependent two-dimensional motion of small, spherical gas bubbles in a bubble column operating in the homogeneous regime. The motion of these bubbles is calculated from a force balance for each individual bubble, accounting for
Modelling of Spherical Gas Bubble Oscillations and Sonoluminescence
NASA Technical Reports Server (NTRS)
Prosperetti, A.; Hao, Y.
The discovery of single-bubble sonoluminescence has led to a renewed interest in the forced radial oscillations of gas bubbles. Many of the more recent studies devoted to this topic have used several simplifications in the modelling, and in particular in accounting for liquid compressibility and thermal processes in the bubble. In this paper the significance of these simplifications is explored by contrasting the results of Lohse and co-workers with those of a more detailed model. It is found that, even though there may be little apparent difference between the radius-versus time behaviour of the bubble as predicted by the two models, quantities such as the spherical stability boundary and the threshold for rectified diffusion are affected in a quantitatively significant way. These effects are a manifestation of the subtle dependence upon dissipative processes of the phase of radial motion with respect to the driving sound field. The parameter space region, where according to the theory of Lohse and co-workers, sonoluminescence should be observable, is recalculated with the new model and is found to be enlarged with respect to the earlier estimate. The dependence of this parameter region on sound frequency is also illustrated.
Hydrodynamics of Fischer-Tropsch synthesis in slurry bubble column reactors: Final report
Bukur, D.B.; Daly, J.G.; Patel, S.A.; Raphael, M.L.; Tatterson, G.B.
This report describes studies on hydrodynamics of bubble columns for Fischer-Tropsch synthesis. These studies were carried out in columns of 0.051 m and 0.229 m in diameter and 3 m tall to determine effects of operating conditions (temperature and gas flow rate), distributor type (sintered metal plate and single and multi-hole perforated plates) and liquid media (paraffin and reactor waxes) on gas hold-up and bubble size distribution. In experiments with the Fischer-Tropsch (F-T) derived paraffin wax (FT-300) for temperatures between 230 and 280/sup 0/C there is a range of gas velocities (transition region) where two values of gas hold-up (i.e., two flow regimes) are possible. Higher hold-ups were accompanied by the presence of foam (''foamy'' regime) whereas lower values were obtained in the absence of foam (''slug flow'' in the 0.051 m column, or ''churn-turbulent'' flow regime in the 0.229 m column). This type of behavior has been observed for the first time in a system with molten paraffin wax as the liquid medium. Several factors which have significant effect on foaming characteristics of this system were identified. Reactor waxes have much smaller tendency to foam and produce lower hold-ups due to the presence of larger bubbles. Finally, new correlations for prediction of the gas hold-up and the specific gas-liquid interfacial area were developed on the basis of results obtained in the present study. 49 refs., 99 figs., 19 tabs.
A computational model of gas bubble evolution in liquid filled straight tubes
NASA Astrophysics Data System (ADS)
Himm, Jeff; Halpern, David
Deep sea divers suffer from decompression sickness (DCS) when their rate of ascent to the surface is too quick. When the ambient pressure drops, inert gas bubbles are usually formed in blood vessels and tissues of divers. It is believed that the existence of gas bubbles is the cause of DCS that manifests itself as itching, joint pain, and neurological abnormalities. While models of gas bubbles in tissues are relatively well developed, the mechanism of bubble growth in the circulation is far less well understood. The existence of gas bubbles may affect gas exchange in small blood vessels by blocking the flow of blood. Gas bubble evolution in the circulation is investigated using an analytical method for small bubbles and the boundary element method for bubbles whose effective radius is close to the tube radius. The concentration field for the dissolved gas surrounding the bubble is solved numerically using finite differences. The bubble volume is adjusted over time according to the mass flux at the surface. It is shown that the effect of increasing the flow rate is to enhance bubble evolution, up to a factor of two compared with the evolution in tissue where there is no flow. This work was supported by the Naval Medical Research and Development Command work unit 62233N.MM33P30.0041509.
In-water gas combustion in linear and annular gas bubbles
NASA Astrophysics Data System (ADS)
Teslenko, V. S.; Drozhzhin, A. P.; Medvedev, R. N.; Batraev, I. S.
A new pulsed-cyclic method of in-water gas combustion was developed with separate feed of fuel gas and oxygen with the focus on development of new technologies for heat generators and submerged propellers. The results of calorimetric and hydrodynamic measurements are presented. In-water combustion of acetylene, hydrogen, and propane was tested with the operation frequency of 2-2.5 Hz and with a linear injector. The combustion dynamics of combustion of stoichiometric mixture with propane (C3H8+5O2) was studied for a bubble near a solid wall; the produced gas bubble continues expansion and oscillations (for the case of linear and annular bubbles). It was demonstrated that gas combustion in annular bubbles produces two same-magnitude pulses of force acting on the wall. The first pulse is produced due to expansion of combustion products, and the second pulse is produced due to axial cumulative processes after bubble collapse. This process shapes an annular vortex which facilitates high-speed convective processes between combustion products and liquid; and this convection produces small-size bubbles.
Heat transfer and hydrodynamics in a three-phase slurry bubble column
H. Li; A. Prakash
The instantaneous and time-averaged heat transfer coefficients in the regions near the wall and at the center and average gas holdups were measured in a 0.28 m diameter slurry bubble column for the air-water and air-water-glass beads (35 ö¥m) system. The effects of high gas velocities (up to 0.35 m\\/s) and high solids concentrations (up to 40 vol %) were
Measurements of heat transfer coefficient between an immersed surface and surrounding two- and three-phase dispersions have been conducted as a function of gas velocity in a cylindrical bubble column equipped with either a single axial tube or a seven-tube bundle at 309?K. Gas holdup is also measured under the same conditions. In particular, the systems that have been investigated are
Evolution of Bubbles through Gas Injection from a Micro-Tube into Liquid Cross-Flow
NASA Astrophysics Data System (ADS)
Ghaemi, Sina; Rahimi, Payam; Nobes, David
Generation of small-size bubbles is of importance in many processes such as chemical, medical and food industries. The most common method of bubble generation is injection of gas from an orifice into the liquid phase. In spite of simplicity of this method, appropriate conditions should exist to avoid bubble growth and obtain required small-size bubbles. Thorough understanding of the bubble formation and growth can reveal the required conditions and ensure detachment of the bubbles from the orifice with desired timing to control their size. In this work, evolution of bubbles from a micro-size gas injection tube into liquid cross-flow is investigated. Special attention has been devoted to optimize the conditions to generate micro-size bubbles. Specifically, the influence of gas injection tube size and location, gas and liquid Reynolds numbers and the geometry of the mixing chamber on the bubbles evolution is studied. High-speed shadowgraphy technique is applied to investigate bubbles size and shape. A Particle Tracking Velocimetry algorithm is also applied to calculate bubbles velocity. The velocity field of the liquid flow surrounding the bubbles is also characterized using a Mirco-Stereo-Particle Image Velocimetry technique.
Effect of gas expansion on the velocity of a Taylor bubble: PIV measurements
R. G. Sousa; A. M. F. R. Pinto; J. B. L. M. Campos
The effect of gas expansion on the velocity of a Taylor bubble was studied experimentally. The velocity field in the liquid ahead of a Taylor bubble was measured by particle image velocimetry (PIV), and the bubble velocity was measured with two pairs of laser diodes and photocells. The experiments were done in a 7.0m long vertical tube with a 32mm
Bubble formation at submerged nozzles for small gas flow rate under low gravity
Hideki Tsuge; Koichi Terasaka; Wataru Koshida; Hirokazu Matsue
To develop gas-liquid contacting processes in space stations, bubble formation at a nozzle submerged in liquid under low gravity was discussed. Effects of gas flow rate and surface tension on bubble formation were experimentally investigated over a 10 s period using the drop shaft of Japan Microgravity Center at Kamisunagawa in Japan. When the gas flow rate is comparatively small,
Rise velocity of a swarm of large gas bubbles in liquids
R. Krishna; M. I. Urseanu; J. M van Baten; J. Ellenberger
This paper develops a procedure for estimation of the rise velocity of a swarm of large gas bubbles in a bubble column operating in the churn-turbulent flow regime. The large bubble swarm velocity is estimated by introducing two correction factors into the classical DaviesTaylor (1950) relation for rise of a single spherical cap bubble in a liquidVb=0.71gdb(SF)(AF).The scale correction factor
Simulation of large bubble/molten steel interaction for gas-injected ladle
NASA Astrophysics Data System (ADS)
Pan, S.-M.; Chiang, J.-D.; Hwang, W.-S.
A mathematical model has been developed to simulate numerically the interactions between gas bubbles and molten steel during the gas-injection treatment in secondary refining of steel and to experimentally verify the reliability of the model. A marker-and-cell (MAC) technique is employed to simulate the motions of gas bubbles and molten steel. Photographic observation is used to evaluate the reliability of the mathematical model. A two-dimensional ladle with only one bubble was used to test the capability of the model to handle the interaction between the relatively large bubble and the molten steel. The shape of the bubble is initially round. Then it gradually becomes flattened and eventually evolves into a spherical-cap bubble. Molten steel is induced to flow and forms two circulations. The model was then tested on the same ladle with bubbles continuously released. The first bubble rises in a similar way as the previous case. The second bubble is affected by the first bubble and becomes slightly elongated in the vertical direction rather than in the horizontal direction. It also rises faster and later collides with the first bubble. The released bubbles can be grouped in clusters and are repeated cluster after cluster. Water-model experimental observations are consistent with the predicted results.
Gas accumulation in particle-rich suspensions and implications for bubble populations in crystal-rich magma
Rempel, Alan W.
in particle-aided bubble coalescence. However, these studies demon- strate that the effect of particles on gasGas accumulation in particle-rich suspensions and implications for bubble populations in crystal between rising bubbles and particles. We observe different interaction styles as the ratio of bubble
Gasliquid mass transfer in a slurry bubble column operated at gas hydrate forming conditions
Shahrzad Hashemi; Arturo Macchi; Phillip Servio
Gasliquid interphase mass transfer was investigated in a slurry bubble column under CO2 hydrate forming operating conditions. Modeling gas hydrate formation requires knowledge of mass transfer and the hydrodynamics of the system. The pressure was varied from 0.1 to 4MPa and the temperature from ambient to 277K while the superficial gas velocity reached 0.20m\\/s. Wettable ion-exchange resin particles were used
Shock-wave propagation in a sonoluminescing gas bubble
C. C. Wu; Paul H. Roberts
The motion of the bubble radius and of the air trapped inside the bubble during sonoluminescence are determined self-consistently by coupling the solution of the Rayleigh-Plesset equation governing the bubble radius to the solution of Euler's equations for the motion of air in the bubble. Results are presented for three slightly different conditions of excitation, in two of which shocks
The formation of gas bubbles at submerged orifices
Hayes, William Bell
into the bubble, evaluated at the downstream conditions, v = volume (spherical) of the bubble at time, t. Furthermore, In the following analysis, the actual bubble was ( 6) First consider the center of a spherical bubble dv dv dD = dD dt (8) and d...D _ TTD2 dr dt ? dt (9) dt = dD where D = diameter of the bubble r = radius of the bubble For convenience, let Vn = H dO)n ax TTD where, Vn = magnitude of the normal velocity of a point on the surface of a bubble whose center is fixed...
Micropumping of liquid by directional growth and selective venting of gas bubbles.
Meng, Dennis Desheng; Kim, Chang-Jin C J
We introduce a new mechanism to pump liquid in microchannels based on the directional growth and displacement of gas bubbles in conjunction with the non-directional and selective removal of the bubbles. A majority of the existing bubble-driven micropumps employs boiling despite the unfavorable scaling of energy consumption for miniaturization because the vapor bubbles can be easily removed by condensation. Other gas generation methods are rarely suitable for micropumping applications because it is difficult to remove the gas bubbles promptly from a pump loop. In order to eradicate this limitation, the rapid removal of insoluble gas bubbles without liquid leakage is achieved with hydrophobic nanopores, allowing the use of virtually any kind of bubbles. In this paper, electrolysis and gas injection are demonstrated as two distinctively different gas sources. The proposed mechanism is first proved by circulating water in a looped microchannel. Using H(2) and O(2) gas bubbles continuously generated by electrolysis, a prototype device with a looped channel shows a volumetric flow rate of 4.5-13.5 nL s(-1) with a direct current (DC) power input of 2-85 mW. A similar device with an open-ended microchannel gives a maximum flow rate of approximately 65 nL s(-1) and a maximum pressure head of approximately 195 Pa with 14 mW input. The electrolytic-bubble-driven micropump operates with a 10-100 times higher power efficiency than its thermal-bubble-driven counterparts and exhibits better controllability. The pumping mechanism is then implemented by injecting nitrogen gas bubbles to demonstrate the flexibility of bubble sources, which would allow one to choose them for specific needs (e.g., energy efficiency, thermal sensitivity, biocompatibility, and adjustable flow rate), making the proposed mechanism attractive for many applications including micro total analysis systems (microTAS) and micro fuel cells. PMID:18497918
Quantification of gas saturations during bubbly gas flow using a novel calibration technique
NASA Astrophysics Data System (ADS)
Hegele, P. R.; Mumford, K. G.
An understanding of gas dynamics is important during the remediation of contaminated soil and groundwater by techniques such as in situ air sparging (IAS) and in situ thermal treatment (ISTT). For example, mass transfer rates between dissolved contaminants and gases are governed by gas-liquid interfacial area, relative permeability effects reduce aqueous flow through a gas-occupied treatment zone, bubble flow allows gas phase transport at lower gas saturations in coarse material, and the onset of gas connection allows increased capture and recovery of gas-phase mass during vapor extraction. Visualization using light transmission methods (i.e., transmitting light through thin experimental cells and capturing digital images of the media and fluids in the cell over time) can be used to investigate gas dynamics in laboratory experiments. These light transmission methods often require calibration to representative wet and dry or residual transmitted light intensities in order to quantify gas saturations. In this work, a new calibration procedure was developed and used to quantify gas saturations during bubbly gas flow in coarse sand, which only used data from the water-saturated image. A known gas volume was injected at slow flow rates into the bottom of a thin cell (100 mm æ 80 mm æ 8 mm) containing water and sand, such that bubbly gas flow occurred. Pixel-wise gas saturation values at multiple points in time during the gas injection were integrated over the volume of the cell and calibrated to the total volume of gas injected. This method was able to overcome experimental difficulties associated with obtaining representative dry or residual images for use in calibration, and was able to calibrate directly to the distribution of discontinuous gas, which resulted in low errors in local gas saturation (i.e., standard deviations of 0.5%-2% with a median filter applied). Calibrated images were used to validate results from a numerical model used to simulate bubbly gas flow in two and three dimensions for use in air sparging applications. In addition, the light transmission method was applied to laboratory experiments of ISTT using electrical resistance heating (ERH) to investigate the development of a gas phase during boiling.
Can Propagation of Gas Bubbles Lead to Detached Solidification? Experiments on Freezing of Water
Regel, Liya L.
Yazhen Wang, Liya L. Regel,* and William R. Wilcox* International Center for Gravity Materials Science the freezing interface influenced gas bubble formation, and was outward for a concave freezing interface an organic compound, naphthalene.20 The formation and behavior of gas bubbles at a freezing interface can
Technology Transfer Automated Retrieval System (TEKTRAN)
Recent studies have shown the production of significant amounts of benign nitrogen gas (N2) in anaerobic swine lagoons. The gas is found in bubbles collected below the lagoon surface. Contamination of these bubbles by N2 from the atmosphere cannot be excluded. Therefore, a model was developed with t...
Gas embolotherapy: Bubble evolution in acoustic droplet vaporization and design of a benchtop microvascular model
Zheng Zheng Wong
This work was motivated by an ongoing development of a potential embolotherapy technique to occlude blood flow to tumors using gas bubbles selectively formed by in vivo acoustic droplet vaporization (ADV) of liquid perfluorocarbon droplets. Mechanisms behind the ADV, transport and lodging of emboli need to be understood before gas embolotherapy can translate to the clinic. Evolution of a bubble
Venous gas embolism: time course of residual pulmonary intravascular bubbles.
Butler, B D; Luehr, S; Katz, J
The time course of pulmonary intravascular air emboli was studied in anesthetized dogs. In one series of experiments air was infused into the right atrium at 0.10 ml.kg-1.min-1 or 0.25 ml.kg-1.min-1 for 15 min or given as a bolus injection of 2 ml/kg at 2 ml/sec. In a second series of series of experiments venous air was infused into dogs (0.25 ml.kg-1.min-1, 15 min) ventilated with 100% oxygen for 0, 30, or 210 min before the embolization. After the air infusions the animals were allowed to recover, breathing 70% nitrogen:30% oxygen. At 10-min intervals during recovery, the nitrogen was replaced with nitrous oxide (N2O) for 5 min to expand any residual pulmonary vascular bubbles. Subsequent changes in pulmonary artery pressure (Ppa) and end-tidal carbon dioxide (PETCO2) concentrations, pulmonary vascular resistance (PVR) and carbon dioxide tensions (PaCO2) as a result of the N2O challenges indicated the presence of residual gas bubbles in the pulmonary arterial system. Residual times of the pulmonary bubbles were 24.5 +/- 12.3 min (0.10 ml.kg-1.min-1 air dose), 43 +/- 10.8 min (0.25 ml.kg-1.min-1 air dose), and 17.8 +/- 2.5 min (bolus). The latter two were significantly different from each other. With 100% oxygen breathing the residual times were 19 +/- 2.2 (0 min), 22 +/- 6.7 min (30 min), and 17 +/- 4.0 (210 min). These values were reduced significantly when compared to the dogs ventilated with 30% oxygen.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2929052
Axial solid distribution in slurry bubble columns
Murray, P.; Fan, L.-S. (Dept of Chemical Engineering, The Ohio State Univ, Columbus, OH (US))
The axial sold concentration distribution in a slurry bubbly column was studied in both batch and continuous operation. Air and water were used as the gas and liquid phases, respectively. The gas velocity ranged from 0.016 to 0.173 m/s, and the slurry velocity ranged from 0.0 to 0.031 m/s. Glass beads of diameters 163,97, and 49 {mu}m were used as the solid phase. The holdup distribution of each solid in binary mixtures was also studied. The effects of gas velocity, slurry velocity, and particle size on the axial solid concentration distribution were examined. A mechanistic model is developed to describe the solid distribution in the slurry bubble columns. The model accounts for the solid distribution for both batch and continuous operation involving monodispersed and binary mixtures of solid particles.
Gas Bubbles and Gas Pancakes at Liquid/Solid Interface: A Continuum Theory Incorporated with Molecular Interactions
Zhaoxia Li; Xuehua Zhang; Lijuan Zhang; Xiaocheng Zeng; Jun Hu; Haiping Fang
The states of gas accumulated at the liquid-solid interface are analyzed based on the continuum theory where the Hamaker constant is used to describe the long-range interaction at the microscopic scale. The Hamaker constant is always negative, whereas the gas spreading coefficient can be either sign. Despite the complexity of gas, including that the density profile may not be uniform due to absorption on both solid and liquid surfaces, we predict three possible gas states at the liquid-solid interface, i.e. complete wetting, partial wetting and pseudopartial wetting. These possible gas states correspond respectively to a gas pancake (or film) surrounded by a wet solid, a gas bubble with a finite contact angle, and a gas bubble(s) coexisting with a gas pancake. Typical thickness of the gas pancakes is at the nanoscale within the force range of the long-range interaction, whereas the radius of the gas bubbles can be large. The state of gas bubble(s) coexisting with a gas film is predicted theoretically for the first time. Our theoretical results can contribute to the development of a unified picture of gas nucleation at the liquid-solid interface.
Decompression vs. Decomposition: Distribution, Amount, and Gas Composition of Bubbles in Stranded Marine Mammals
de Quirµs, Yara Bernaldo; GonzÃlez-Diaz, Oscar; Arbelo, Manuel; Sierra, Eva; Sacchini, Simona; FernÃndez, Antonio
Gas embolic lesions linked to military sonar have been described in stranded cetaceans including beaked whales. These descriptions suggest that gas bubbles in marine mammal tissues may be more common than previously thought. In this study we have analyzed gas amount (by gas score) and gas composition within different decomposition codes using a standardized methodology. This broad study has allowed us to explore species-specific variability in bubble prevalence, amount, distribution, and composition, as well as masking of bubble content by putrefaction gases. Bubbles detected within the cardiovascular system and other tissues related to both pre- and port-mortem processes are a common finding on necropsy of stranded cetaceans. To minimize masking by putrefaction gases, necropsy, and gas sampling must be performed as soon as possible. Before 24?h post mortem is recommended but preferably within 12?h post mortem. At necropsy, amount of bubbles (gas score) in decomposition code 2 in stranded cetaceans was found to be more important than merely presence vs. absence of bubbles from a pathological point of view. Deep divers presented higher abundance of gas bubbles, mainly composed of 70% nitrogen and 30% CO2, suggesting a higher predisposition of these species to suffer from decompression-related gas embolism. PMID:22675306
Nonlinear exactly solvable wave dynamic models for liquids containing gas bubbles
NASA Astrophysics Data System (ADS)
Din Cher, Kim
Exactly solvable wave dynamic models for liquids containing gas bubbles are presented. Lighthill's generalized inhomogeneous wave equation is first derived for a host liquid where the gas phase is presented by an equivalent distribution of monopole sources. The complete effects of nonlinear bubble dynamics and the change of bubble number density in a pressure field are included. An exact numerical method, where individual bubbles are traced to estimate their radial dynamics and the full volumetric change of the wave phenomena, is developed and programmed for solution on a computer.
Shock-wave propagation in a sonoluminescing gas bubble
NASA Technical Reports Server (NTRS)
Wu, C. C.; Roberts, Paul H.
The motion of the bubble radius and of the air trapped inside the bubble during sonoluminescence are determined self-consistently by coupling the solution of the Rayleigh-Plesset equation governing the bubble radius to the solution of Euler's equations for the motion of air in the bubble. Results are presented for three slightly different conditions of excitation, in two of which shocks are formed during the collapse of the bubble, and in which such high temperatures are attained that the air is ionized. Estimates are made of the duration and intensity of the light then radiated by the plasma.
Direct numerical simulation of single gas bubbles in pure and contaminated liquids
Peter Lakshmanan; Peter Ehrhard
Disperse gas bubbles play an important role in many industrial applications. Knowing the rising velocity, the interfacial area, or the critical size for break-up or coalescence in different systems can be crucial for the process design. Hence, knowing the fundamental behaviour of a single bubble appears mandatory for the examination of bubble swarms and for the Euler-Lagrange or Euler--Euler modelling
Instability of interfaces of gas bubbles in liquids under acoustic excitation with dual frequency.
Zhang, Yuning; Du, Xiaoze; Xian, Haizhen; Wu, Yulin
Instability of interfaces of gas bubbles in liquids under acoustic excitation with dual frequency is theoretically investigated. The critical bubble radii dividing stable and unstable regions of bubbles under dual-frequency acoustic excitation are strongly affected by the amplitudes of dual-frequency acoustic excitation rather than the frequencies of dual-frequency excitation. The limitation of the proposed model is also discussed with demonstrating examples. PMID:25164271
Hydroacoustic detection and quantification of free gas -methane bubbles- in the ocean
NASA Astrophysics Data System (ADS)
Greinert, J.; Artemov, Y.; Gimpel, P.
Extensive methane release as a free gas phase from cold vents is well known from deep (>2000m) and shallow (10s of meters) water depths. Supposedly, much more methane is transported into the water column by free gas than by dissolved gas, which is oxidized by anaerobic and aerobic processes and partly precipitated as carbonate. Rising gas bubbles are not affected by this 'filter' mechanisms. Because of the strength of the backscattered signal from gas bubbles in the water column, bubbles can be detected by single-beam or multi-beam echosounder systems. Thus, hydroacoustic systems with different frequencies can be used to 1) detect free gas in the water column, 2) map the distribution of active vent sites which release free gas, 3) monitor a possible periodicity in the release of bubbles induced by e.g. tides or currents, 4) quantify the gas volume and gas flux that is released in a local area or larger region. In the German research project LOTUS we use ship- mounted single-beam echosounders to map gas plumes (flares) and investigate their periodicity (Flare Imaging). Using specialized single-beam echosounder systems makes it possible to measure the bubble sizes and their distribution. In combination with the volume of the backscattering strength these measurements can be used to estimate the gas volume in a defined part of the water body. Though gas bubbles rise in the water column, they are - particularly methane - rapidly dissolved and thus become smaller. Their rising speed as well as their diminishing size can be determined, which helps to understand the dissolution behaviour of methane bubbles; they form a hydrate skin at distinct pressure and temperature conditions. For a detailed, long-term observation of active bubble-expulsing areas we developed a lander based 180 kHz multi beam system that 'looks' horizontally (GasQuant). The system records backscatter data from a 75¯ swath that covers an area of about 5300m2. Via calibration we can quantify the methane flux of every single bubble-vent and calculate the methane flux of a bubble vent area. Both hydroacoustic techniques were used during several cruises in 2002 to investigate bubble vents at Hydrate Ridge (HR), offshore Oregon. Several bubble-vent areas were detected at the northern summit of HR. They are related to carbonate chemoherms and morphological heights but were also found in areas which do not show any of these features. The GasQuant system was successfully deployed at the northern and southern summit. The data processing is currently in progress.
NSDL National Science Digital Library
Mercer Mayer
With magic bubble solution, a boy discovers that he can blow any kind of bubble imaginable: a kangaroo, a bird, a car, or a boat. Mercer Mayer's colorful illustrations enliven this engaging tale of mysterious bubbles.
The effect of bubble-mediated gas transfer on purposeful dual-gaseous tracer experiments
William E. Asher; Rik Wanninkhof
For air-water gas exchange across unbroken surfaces, the only gas-dependent parameter affecting the transfer velocity is the molecular diffusivity of the transferring species. In contrast, bubble-mediated transfer processes can cause the transfer velocity to depend on both molecular diffusivity and aqueous-phase solubility. This can complicate the analysis of data from dual-gaseous tracer gas transfer experiments. Bubble effects also complicate the
The effect of anaesthesia on the intraocular volume of the C3F8 gas bubble
M Briggs; D Wong; C Groenewald; J McGalliard; J Kelly; J Harper
Long-acting intraocular gas bubbles are frequently used during vitrectomy to tamponade retinal breaks. The aim of this study was to determine the effect of nitrous oxide anaesthesia on the size and effectiveness of the post-vitrectomy gas bubble. Twenty vitrectomy procedures with injection of 12% perfluoropropane (C3F8) gas were performed. For 10 of the cases routine anaesthesia with nitrous oxide was
Optically actuated thermocapillary movement of gas bubbles on an absorbing substrate
Ohta, Aaron T.; Jamshidi, Arash; Valley, Justin K.; Hsu, Hsan-Yin; Wu, Ming C.
The authors demonstrate an optical manipulation mechanism of gas bubbles for microfluidic applications. Air bubbles in a silicone oil medium are manipulated via thermocapillary forces generated by the absorption of a laser in an amorphous silicon thin film. In contrast to previous demonstrations of optically controlled thermally driven bubble movement, transparent liquids can be used, as the thermal gradient is formed from laser absorption in the amorphous silicon substrate, and not in the liquid. A variety of bubbles with volumes ranging from 19 pl to 23 nl was transported at measured velocities of up to 1.5 mm/s. PMID:19750203
Heat transfer and bubble dynamics in slurry bubble columns for Fischer-Tropsch clean alternative energy
NASA Astrophysics Data System (ADS)
Wu, Chengtian
With the increasing demand for alternative energy resources, the Fischer-Tropsch (FT) process that converts synthesis gas into clean liquid fuels has attracted more interest from the industry. Slurry bubble columns are the most promising reactors for FT synthesis due to their advantages over other reactors. Successful operation, design, and scale-up of such reactors require detailed knowledge of hydrodynamics, bubble dynamics, and transport characteristics. However, most previous studies have been conducted at ambient pressure or covered only low superficial gas velocities. The objectives of this study were to experimentally investigate the heat transfer coefficient and bubble dynamics in slurry bubble columns at conditions that can mimic FT conditions. The air-C9C 11-FT catalysts/glass beads systems were selected to mimic the physical properties of the gas, liquid, and solid phases at commercial FT operating conditions. A heat transfer coefficient measurement technique was developed, and for the first time, this technique was applied in a pilot scale (6-inch diameter) high pressure slurry bubble column. The effects of superficial gas velocity, pressure, solids loading, and liquid properties on the heat transfer coefficients were investigated. Since the heat transfer coefficient can be affected by the bubble properties (Kumar et al., 1992), in this work bubble dynamics (local gas holdup, bubble chord length, apparent bubble frequency, specific interfacial area, and bubble velocity) were studied using the improved four-point optical probe technique (Xue et al., 2003; Xue, 2004). Because the four-point optical technique had only been successfully applied in a churn turbulent flow bubble column (Xue, 2004), this technique was first assessed in a small scale slurry bubble column in this study. Then the bubble dynamics were studied at the same conditions as the heat transfer coefficient investigation in the same pilot scale column. The results from four-point probe bubble dynamics study advanced the understanding of heat transfer in the slurry bubble column. This study also provides important benchmark information for the slurry bubble column design and the evaluation of computational fluid dynamics (CFD) simulations.
Heat transfer investigations in a slurry bubble column
Saxena, S.C.; Rao, N.S.; Vadivel, R.; Shrivastav, S.; Saxena, A.C.; Patel, B.B.; Thimmapuram, P.R.; Kagzi, M.Y.; Khan, I.A.; Verma, A.K.
Slurry bubble columns, for use in Fischer-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven-, or thirty-seven tubes. the experiments were conducted for two- and three phase systems; employing for gas phase: air and nitrogen, liquid phase: water and Therminol-66, and solid phase: red iron oxide (1.02, 1.70 and 2.38 {mu}m), glass beads (50.0, 90.0, 119.0 and 143.3 {mu}m), silica sand (65 {mu}m), and magnetite (28.0, 35.7, 46.0, 58.0, 69.0, 90.5, 115.5 and 137.5 {mu}m). The column temperature was varied between 298--523 K, gas velocity between 0--40 cm/s, and solids concentration between 0--50 weight percent. The holdup and heat transfer data as a function of operating and system parameters were employed to assess the available correlations and semitheoretical models, and to develop new correlations. Information concerning the design and scale-up of larger units is presented. Specific research work that need to be undertaken to understand the phenomena of heat transfer and gas holdup is outlined so that efficient gas conversion and catalyst usage may be accomplished in slurry bubble columns. 28 refs., 102 figs., 42 tabs.
Heat transfer investigations in a slurry bubble column
Saxena, S.C.; Rao, N.S.; Vadivel, R.; Shrivastav, S.; Saxena, A.C.; Patel, B.B.; Thimmapuram, P.R.; Kagzi, M.Y.; Khan, I.A.; Verma, A.K.
Slurry bubble columns, for use in Fisher-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven- or thirty-seven tubes. The experiments were conducted for two- and three-phase systems; employing for gas phase: air and nitrogen, liquid phase: water and Therminol-66, and solid phase: red iron oxide (1.02, 1.70 and 2.38 {mu}m), glass beads (50.0, 90.0, 119.0 and 143.3 {mu}m), silica sand (65 {mu}), and magnetite (28.0, 35.7, 46.0, 58.0, 69.0, 90.5, 115.5, and 137.5 {mu}m). The column temperature was varied between 298--523 K, gas velocity between 0--40 cm/s, and solids concentration between 0--50 weight percent. The holdup and heat transfer data as a function of operating and system parameters were employed to assess the available correlations and semitheoretical models, and to develop new correlations. Information concerning the design and scale-up of larger units is presented. Specific research work that need to be undertaken to understand the phenomena of heat transfer and gas holdup is outlined so that efficient gas conversion and catalyst usage may be accomplished in slurry bubble columns. 130 refs., 177 figs., 54 tabs.
Bernard A. Toseland, Ph.D.
The major technical objectives of this program are threefold: (1) to develop the design tools and a fundamental understanding of the fluid dynamics of a slurry bubble column reactor to maximize reactor productivity, (2) to develop the mathematical reactor design models and gain an understanding of the hydrodynamic fundamentals under industrially relevant process conditions, and (3) to develop an understanding of the hydrodynamics and their interaction with the chemistries occurring in the bubble column reactor. Successful completion of these objectives will permit more efficient usage of the reactor column and tighter design criteria, increase overall reactor efficiency, and ensure a design that leads to stable reactor behavior when scaling up to large diameter reactors. The past three months of research have been focused on two major areas of bubble column hydrodynamics: (1) pressure and temperature effects on gas holdup and (2) region transition using a sparger as a gas distributor.
A Study of Bubble and Slug Gas-Liquid Flow in a Microgravity Environment
NASA Technical Reports Server (NTRS)
McQuillen, J.
The influence of gravity on the two-phase flow dynamics is obvious.As the gravity level is reduced,there is a new balance between inertial and interfacial forces, altering the behavior of the flow. In bubbly flow,the absence of drift velocity leads to spherical-shaped bubbles with a rectilinear trajectory.Slug flow is a succession of long bubbles and liquid slug carrying a few bubbles. There is no flow reversal in the thin liquid film as the long bubble and liquid slug pass over the film. Although the flow structure seems to be simpler than in normal gravity conditions,the models developed for the prediction of flow behavior in normal gravity and extended to reduced gravity flow are unable to predict the flow behavior correctly.An additional benefit of conducting studies in microgravity flows is that these studies aide the development of understanding for normal gravity flow behavior by removing the effects of buoyancy on the shape of the interface and density driven shear flows between the gas and the liquid phases. The proposal calls to study specifically the following: 1) The dynamics of isolated bubbles in microgravity liquid flows will be analyzed: Both the dynamics of spherical isolated bubbles and their dispersion by turbulence, their interaction with the pipe wall,the behavior of the bubbles in accelerated or decelerated flows,and the dynamics of isolated cylindrical bubbles, their deformation in accelerated/decelerated flows (in converging or diverging channels), and bubble/bubble interaction. Experiments will consist of the use of Particle Image Velocimetry (PIV) and Laser Doppler Velocimeters (LDV) to study single spherical bubble and single and two cylindrical bubble behavior with respect to their influence on the turbulence of the surrounding liquid and on the wall 2) The dynamics of bubbly and slug flow in microgravity will be analyzed especially for the role of the coalescence in the transition from bubbly to slug flow (effect of fluid properties and surfactant), to identify clusters that promote coalescence and transition the void fraction distribution in bubbly and slug flow,to measure the wall friction in bubbly flow. These experiments will consist of multiple bubbles type flows and will utilize hot wire and film anemometers to measure liquid velocity and wall shear stress respectively and double fiber optic probes to measure bubble size and velocity as a function of tube radius and axial location.
Laser generation of gas bubbles: Photoacoustic and photothermal effects recorded in transient grating experiments
Frez, Clifford; Diebold, Gerald J. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)
Absorption of high power laser radiation by colloidal suspensions or solutions containing photoreactive chemicals can result in bubble production. Here, transient grating experiments are reported where picosecond and nanosecond lasers are used to initiate photoinduced processes that lead to bubble formation. Irradiation of colloidal Pt suspensions is found to produce water vapor bubbles that condense back to liquid on a nanosecond time scale. Laser irradiation of Pt suspensions supersaturated with CO{sub 2} liberates dissolved gas to produce bubbles at the sites of the colloidal particles. Laser induced chemical reactions that produce bubbles are found in suspensions of particulate C in water, and in the sensitized decarboxylation of oxalic acid. Theory based on linear acoustics as well as the Rayleigh-Plesset equation is given for description of the bubble motion.
Laser generation of gas bubbles: Photoacoustic and photothermal effects recorded in transient grating experiments.
Frez, Clifford; Diebold, Gerald J
Absorption of high power laser radiation by colloidal suspensions or solutions containing photoreactive chemicals can result in bubble production. Here, transient grating experiments are reported where picosecond and nanosecond lasers are used to initiate photoinduced processes that lead to bubble formation. Irradiation of colloidal Pt suspensions is found to produce water vapor bubbles that condense back to liquid on a nanosecond time scale. Laser irradiation of Pt suspensions supersaturated with CO(2) liberates dissolved gas to produce bubbles at the sites of the colloidal particles. Laser induced chemical reactions that produce bubbles are found in suspensions of particulate C in water, and in the sensitized decarboxylation of oxalic acid. Theory based on linear acoustics as well as the Rayleigh-Plesset equation is given for description of the bubble motion. PMID:19045413
Bubble Size Control to Improve Oxygen-Based Bleaching: Characterization of Flow Regimes in Pulp-Water-Gas Three-Phase Flows
S.M. Ghiaasiaan and Seppo Karrila
Flow characteristics of fibrous paper pulp-water-air slurries were investigated in a vertical circular column 1.8 m long, with 5.08 cm diameter. Flow structures, gas holdup (void fraction), and the geometric and population characteristics of gas bubbles were experimentally investigated, using visual observation, Gamma-ray densitometry, and flash X-ray photography. Five distinct flow regimes could be visually identified: dispersed bubbly, layered bubbly, plug, churn-turbulent, and slug. Flow regime maps were constructed, and the regime transition lines were found to be sensitive to consistency. The feasibility of using artificial neural networks (ANNs) for the identification of the flow regimes, using the statistical characteristics of pressure fluctuations measured by a single pressure sensor, was demonstrated. Local pressure fluctuations at a station were recorded with a minimally-intrusive transducer. Three-layer, feed-forward ANNs were designed that could identify the four major flow patterns (bubbly, plug, churn, and slug) well. The feasibility of a transportable artificial neural network (ANN) - based technique for the classification of flow regimes was also examined. Local pressures were recorded at three different locations using three independent but similar transducers. An ANN was designed, trained and successfully tested for the classification of the flow regimes using one of the normalized pressure signals (from Sensor 1). The ANN trained and tested for Sensor 1 predicted the flow regimes reasonably well when applied directly to the other two sensors, indicating a good deal of transportability. An ANN-based method was also developed, whereby the power spectrum density characteristics of other sensors were adjusted before they were used as input to the ANN that was based on Sensor 1 alone. The method improved the predictions. The gas-liquid interfacial surface area concentration was also measured in the study. The gas absorption technique was applied, using CO2 as the transferred species and sodium hydroxide as the alkaline agent in water. Statistical analysis was performed to identify the parametric dependencies. The experimental data were empirically correlated.
Phase-field simulations of intragranular fission gas bubble evolution in UO2 under post-irradiation thermal annealing
Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert O.; Gao, Fei; Sun, Xin
Fission gas bubble is one of evolving microstructures, which affect thermal mechanical properties such as thermo-conductivity, gas release, volume swelling, and cracking, in operating nuclear fuels. Therefore, fundamental understanding of gas bubble evolution kinetics is essential to predict the thermodynamic property and performance changes of fuels. In this work, a generic phasefield model was developed to describe the evolution kinetics of intra-granular fission gas bubbles in UO2 fuels under post-irradiation thermal annealing conditions. Free energy functional and model parameters are evaluated from atomistic simulations and experiments. Critical nuclei size of the gas bubble and gas bubble evolution were simulated. A linear relationship between logarithmic bubble number density and logarithmic mean bubble diameter is predicted which is in a good agreement with experimental data.
Mathematical Model For Bubbly Water-Heavy Oil-Gas Flow in Vertical Pipes
O. Cazarez-Candia; D. Montoya-HernÃndez; A. G. Vital-Ocampo
In this work a unidimensional, time-dependent homogeneous mathematical model is presented. The model is able to predict pressure, temperature and velocity profiles of the flow known as bubbly-gasbubbly-oil, which can be present when water-heavy oil and gas flow simultaneously in vertical pipes. The mathematical model consists of mass, momentum, and energy conservation equations and its numerical solution is based on
Comments on ``Behaviour of inert gas bubbles under chemical concentration gradients'' by G.P. Tiwari
NASA Astrophysics Data System (ADS)
Evans, J. H.; van Veen, A.
The motion of inert gas bubbles induced by thermal vacancy gradients has previously been used by the present authors to understand gas bubble release in UO 2 and metals. This approach has been recently questioned by Tiwari. In the present letter, a critical discussion of his viewpoint is presented, together with an analysis of the important experimental results of Marachov et al. There appears to be good evidence for the disputed effect.
Statistical estimation of process holdup
Harris, S P
Estimates of potential process holdup and their random and systematic error variances are derived to improve the inventory difference (ID) estimate and its associated measure of uncertainty for a new process at the Savannah River Plant. Since the process is in a start-up phase, data have not yet accumulated for statistical modelling. The material produced in the facility will be a very pure, highly enriched 235U with very small isotopic variability. Therefore, data published in LANL's unclassified report on Estimation Methods for Process Holdup of a Special Nuclear Materials was used as a starting point for the modelling process. LANL's data were gathered through a series of designed measurements of special nuclear material (SNM) holdup at two of their materials-processing facilities. Also, they had taken steps to improve the quality of data through controlled, larger scale, experiments outside of LANL at highly enriched uranium processing facilities. The data they have accumulated are on an equipment component basis. Our modelling has been restricted to the wet chemistry area. We have developed predictive models for each of our process components based on the LANL data. 43 figs.
Holdup measurement for nuclear fuel manufacturing plants
Zucker, M.S.; Degen, M.; Cohen, I.; Gody, A.; Summers, R.; Bisset, P.; Shaub, E.; Holody, D.
The assay of nuclear material holdup in fuel manufacturing plants is a laborious but often necessary part of completing the material balance. A range of instruments, standards, and a methodology for assaying holdup has been developed. The objectives of holdup measurement are ascertaining the amount, distribution, and how firmly fixed the SNM is. The purposes are reconciliation of material unbalance during or after a manufacturing campaign or plant decommissioning, to decide security requirements, or whether further recovery efforts are justified.
Carbonic Anhydrase Activities from the Rainbow Trout Lens Correspond to the Development of Acute Gas Bubble Disease
Nejdet G■ltepe; Orhan Ate?; Olcay Hisar; ?■kr■ Beydemir
Dissolved gas supersaturation is hazardous to fish and can result in gas bubble disease (GBD). Signs of GBD typically include bubbles in the eyes, fins, skin, lateral line, and gill filaments. Ocular abnormalities in diseased salmonids typically occur after aberrant gas production in the eyes. In this study, freshwater rainbow trout Oncorhynchus mykiss were exposed experimentally to percent total gas
Measurement and Analysis of Gas Bubbles Near a Reference Electrode in Aqueous Solutions
Supathorn Phongikaroon; Steve Herrmann; Shelly Li; Michael Simpson
Bubble size distributions (BSDs) near a reference electrode (RE) in aqueous glycerol solutions of an electrolyte NaCl have been investigated under various gas superficial velocities (U{sub S}). BSD and voltage reading of the solution were measured by using a high-speed digital camera and a pH/voltage meter, respectively. The results show that bubble size (b) increases with liquid viscosity ({mu}{sub c}) and U{sub S}. Self-similarity is seen and can be described by the log-normal form of the continuous number frequency distribution. The result shows that b controls the voltage reading in each solution. As b increases, the voltage increases because of gas bubbles interrupting their electrolyte paths in the solutions. An analysis of bubble rising velocity reveals that Stokes Law should be used cautiously to describe the system. The fundamental equation for bubble formation was developed via Newton's second law of motion and shown to be the function of three dimensionless groups--Weber number, Bond number, and Capillary number. After linking an electrochemical principle in the practical application, the result indicates that the critical bubble size is {approx}177 {micro}m. Further analysis suggests that there may be 3000 to 70,000 bubbles generated on the anode surface depending on the size of initial bubbles and provides the potential cause of the efficiency drop observed in the practical application.
Development of New Geothermal Wellbore Holdup Correlations Using Flowing Well Data
Garg, S.K.; Pritchett, J.W.; Alexander, J.H.
An ability to predict both the quantity of fluid that can be produced and its thermodynamic state (pressure, temperature, enthalpy, gas content, salinity, etc.) is essential for estimating the total usable energy of a geothermal resource. Numerical reservoir simulators can be utilized to calculate the thermodynamic state of the fluid at the underground feed-zone(s) at which the fluid enters the wellbore. The computation of the well-head fluid properties from a given underground state (or vice-versa) requires the use of a wellbore simulator. The fluid flow in the wellbore is not amenable to strict analytical treatment. Depending upon the relative amounts of gas and liquid, a variety of flow patterns can occur in the pipe. At small gas loadings, bubble flow takes place. An increase in gas flow rate can result in slug, churn or annular flow. Existing methods for treating two-phase flow in a wellbore require use of empirical correlations for action factor and for liquid hold-up.
Gas accumulation in particle-rich suspensions and implications for bubble populations in crystal-rich magma
NASA Astrophysics Data System (ADS)
Belien, Isolde B.; Cashman, Katharine V.; Rempel, Alan W.
Gas mobility plays an important role in driving volcanic eruptions and controlling eruption style. The explosivity of an eruption depends, among other factors, on how easily gas can escape from the magma. Many magmatic systems have high concentrations of suspended crystals that inhibit gas migration through the melt. We use suspensions of plastic beads in corn syrup to investigate interactions between rising bubbles and particles. We observe different interaction styles as the ratio ? of bubble to particle size is varied. Large bubbles (? > 1) deform and sometimes break up as they move around particles. Small bubbles (? < 1) are frequently trapped within the suspension, increasing the concentration of gas held within the system. We compare our experiments to bubble populations in tephra from Stromboli volcano, Italy. We show that these samples typically have bubbles and crystals of similar sizes and suggest that crystals might play a role in controlling bubble size in this natural system as well as in our experiments. Because small bubbles (? < 1) get trapped within the suspension, and can be formed by breakup of larger bubbles, we expect that an increase in gas flux will result in an increase in the population of small bubbles. Changes in bubble number density and vesicularity in tephra erupted during periods of different eruptive intensity may thus provide a way of tracking changes in gas flux through the magma prior to eruption.
Role of gas density in the stability of single-bubble sonoluminescence M.-C. Chu,2
Yuan, Li
Role of gas density in the stability of single-bubble sonoluminescence L. Yuan,1 C. Y. Ho,2 M of a sonoluminescing bubble interior have shown that the bubble content is compressed to a very dense state during-Taylor instability, but also enhance the threshold of the parametric insta- bility under sonoluminescence conditions
Dynamics of magma flow inside volcanic conduits with bubble overpressure buildup and gas loss through permeable magma
O. Melnik; A. A. Barmin; R. S. J. Sparks
Many volcanic eruptions show transitions between extrusive and explosive behaviour. We develop a new generic model that considers concurrence between pressure buildup in the bubbles due to the viscous resistance to their growth and gas escape through the bubble network as they become interconnected. When the pressure difference between bubbles and magma reaches the strength of the material fragmentation occurs.
Vapor-Gas Bubble Evolution and Growth in Extremely Viscous Fluids Under Vacuum
NASA Technical Reports Server (NTRS)
Kizito, John; Balasubramaniam, R.; Nahra, Henry; Agui, Juan; Truong, Duc
Formation of vapor and gas bubbles and voids is normal and expected in flow processes involving extremely viscous fluids in normal gravity. Practical examples of extremely viscous fluids are epoxy-like filler materials before the epoxy fluids cure to their permanent form to create a mechanical bond between two substrates. When these fluids flow with a free liquid interface exposed to vacuum, rapid bubble expansion process may ensue. Bubble expansion might compromise the mechanical bond strength. The potential sources for the origin of the gases might be incomplete out-gassing process prior to filler application; regasification due to seal leakage in the filler applicator; and/or volatiles evolved from cure reaction products formed in the hardening process. We embarked on a study that involved conducting laboratory experiments with imaging diagnostics in order to deduce the seriousness of bubbling caused by entrained air and volatile fluids under space vacuum and low gravity environment. We used clear fluids with the similar physical properties as the epoxy-like filler material to mimic the dynamics of bubbles. Another aspect of the present study was to determine the likelihood of bubbling resulting from dissolved gases nucleating from solution. These experimental studies of the bubble expansion are compared with predictions using a modified Rayleigh- Plesset equation, which models the bubble expansion.
Gas-bubble growth mechanisms in the analysis of metal fuel swelling
Gruber, E.E.; Kramer, J.M.
During steady-state irradiation, swelling rates associated with growth of fission-gas bubbles in metallic fast reactor fuels may be expected to remain small. As a consequence, bubble-growth mechanisms are not a major consideration in modeling the steady-state fuel behavior, and it is usually adequate to consider the gas pressure to be in equilibrium with the external pressure and surface tension restraint. On transient time scales, however, various bubble-growth mechanisms become important components of the swelling rate. These mechanisms include growth by diffusion, for bubbles within grains and on grain boundaries; dislocation nucleation at the bubble surface, or ''punchout''; and bubble growth by creep. Analyses of these mechanisms are presented and applied to provide information on the conditions and the relative time scales for which the various processes should dominate fuel swelling. The results are compared to a series of experiments in which the swelling of irradiated metal fuel was determined after annealing at various temperatures and pressures. The diffusive growth of bubbles on grain boundaries is concluded to be dominant in these experiments.
Granular temperature distribution in a gas fluidized bed of hollow microparticles prior to onset of bubbling
NASA Astrophysics Data System (ADS)
Xie, L.; Biggs, M. J.; Glass, D.; McLeod, A. S.; Egelhaaf, S. U.; Petekidis, G.
It has been unclear whether bubbles are required to induce particle velocity fluctuations in gas fluidized beds (FBs). We show that bubbles are not necessary by applying diffusing-wave spectroscopy to particles whose minimum bubbling velocity is approximately 5 times that of the minimum fluidization velocity. Fluctuations are first observed at or just above fluidization and increase in magnitude with superficial velocity. The distribution of velocity fluctuations in the bed is also presented: they are symmetrical about the centreline where they are maximal and increase with height above the distributor.
Heating the bubbly gas of galaxy clusters with weak shocks and sound waves
S. Heinz; E. Churazov
Using hydrodynamic simulations and a technique to extract the rotational component of the velocity field, we show how bubbles of relativistic gas inflated by AGN jets in galaxy clusters act as a catalyst, transforming the energy carried by sound and shock waves to heat. The energy is stored in a vortex field around the bubbles which can subsequently be dissipated. The efficiency of this process is set mainly by the fraction of the cluster volume filled by (sub-)kpc scale filaments and bubbles of relativistic plasma.
Ultrasound tomography system used for monitoring bubbly gas\\/liquid two-phase flow
Li-Jun Xu; Ling-An Xu
This paper is about a transmission-mode (TM) ultrasound computerized tomography (UCT) system, which is used to monitor a bubbly gas\\/liquid two-phase flow, a kind of strongly inhomogeneous medium. Because of the high contrast in acoustic impedance distribution of the flow, TM UCT system can only obtain incomplete tomographic projections which depend on the distribution of bubbles in liquid. In order
Measurement and Analysis of Gas Bubbles near a Reference Electrode in
Supathorn Phongikaroon; Steven D. Herrmann; Shelly X. Li; Michael F. Simpson
Bubble size distributions (BSDs) near a reference electrode (RE) in aqueous glycerol solutions of an electrolyte NaCl have been investigated under various gas superficial velocities (Us). BSD and voltage reading of the solution were measured by using a high-speed digital camera and a pH\\/voltage meter, respectively. The results show that bubble size (b) increases with liquid viscosity (äc) and Us.
Kinetics of gas bubble nucleation and growth in magmatic melt at its rapid decompression
NASA Astrophysics Data System (ADS)
Chernov, A. A.; Kedrinsky, V. K.; Pil'nik, A. A.
The model of gas bubble growth in high-viscous gas-saturated magmatic melt, subjected to rapid decompression, is presented in the current study. It is shown that consideration of unsteady character of the process is extremely important in a wide range of supersaturation. The analytical solution is found for the profile of dissolved gas concentration and the rate of bubble growth. The model of kinetics of overall degassing is developed. This model is based on distinguishing the so-called "forbidden" zone in the melt volume with suppressed formation of the new nucleation sites. The simple analytical dependences of the number of nucleating bubbles and typical nucleation time on the value of initial decompression were derived together with time dependence of volumetric concentration of the gas phase. Our results match the available experimental data.
A gas bubble-based parallel micro manipulator: conceptual design and kinematics model
NASA Astrophysics Data System (ADS)
Dong, Wei; Gauthier, MichaŠl; Lenders, Cyrille; Lambert, Pierre
The parallel mechanism has become an alternative solution when micro manipulators are demanded in the fields of micro manipulation and micro assembly. In this technical note, a three-degree-of-freedom (3-DOF) parallel micro manipulator is presented, which is directly driven by three micro gas bubbles. Since the micro gas bubbles are generated and maintained due to the surface tension between the gas and liquid media, the proposed novel system can be used in the liquid environment which allows for rotation about the X and Y axes and translation along the Z axis. In this technical note, the conceptual design of micro gas bubble-based parallel manipulator is introduced and the input/output characteristic of the actuator is analyzed in detail. The kinematics model of the parallel micro manipulator is also established, based on which the workspace and the system motion resolution are analyzed as a criterion and reference for future prototype development.
Gas bubble disease in smallmouth bass and northern squawfish from the Snake and Columbia Rivers
Montgomery, J.C.; Becker, C.D.
In 1975 and 1976, 179 smallmouth bass (Micropterus dolomieui) and 85 northern squawfish (Ptychocheilus oregonensis) were collected by angling from the lower Snake and mid-Columbia rivers, southeastern Washington. All fish were examined externally for gas bubble syndrome. Emboli were found beneath membranes of the opercula, body, and fins of 72% of the smallmouth bass and 84% of the northern squawfish. Hemorrhage was also noted on the caudal, anal, and pectoral fins of several smallmouth bass. Presence of gas bubble syndrome corresponded to the spring runoff when total dissolved gas supersaturations in river water exceeded 115%.
The objective of this study is to develop a predictive experimentally verified computational fluid dynamic (CFD) three phase model. It predicts the gas, liquid and solid hold-ups (volume fractions) and flow patterns in the industrially important bubble-coalesced (churn-turbulent) regime. The input into the model can be either particulate viscosities as measured with a Brookfield viscometer or effective restitution coefficient for
Experimental investigation of a strongly shocked gas bubble.
Ranjan, Devesh; Anderson, Mark; Oakley, Jason; Bonazza, Riccardo
A free-falling, spherical, soap-film bubble filled with argon is subjected to a planar M=2.88 shock in atmospheric nitrogen; vorticity is deposited on the surface of the bubble during shock interaction, and the Richtmyer-Meshkov instability ensues. The geometrical development of the shocked bubble is diagnosed with laser sheet imaging and a planar slice showing two cross sections of both the major vortex ring and a secondary vortex ring is revealed experimentally for the first time. Quantitative measurements of the experimental data include the vortex velocity defect, and subsequent circulation calculations, along with a new set of relevant length scales. The shock wave strength, leading to a post-shock compressible regime, allows the study of the instability development in a regime between low Mach number shock tube experiments and high Mach number laser driven experiments that has not been investigated previously. PMID:15904378
Rate of Disappearance of Gas Bubble Trauma Signs in Juvenile Salmonids
Karen M. Hans; Matthew G. Mesa; Alec G. Maule
To assess the rate of disappearance of gas bubble trauma (GBT) signs in juvenile salmonids, we exposed spring chinook salmon Oncorhynchus tshawytscha and steelhead O. mykiss to water containing high levels of dissolved gas supersaturation (DGS) for a time period sufficient to induce signs of GBT, reduced the DGS to minimal levels, and then sampled fish through time to document
Gas Bubble Disease Monitoring and Research of Juvenile Salmonids : Annual Report 1996.
Maule, Alec G.; Beeman, John W.; Hans, Karen M.; Mesa, M.G.; Haner, P.; Warren, J.J. [Geological Survey, Cook, WA (United States). Columbia River Research Lab.
This document describes the project activities 1996--1997 contract year. This report is composed of three chapters which contain data and analyses of the three main elements of the project: field research to determine the vertical distribution of migrating juvenile salmonids, monitoring of juvenile migrants at dams on the Snake and Columbia rivers, and laboratory experiments to describe the progression of gas bubble disease signs leading to mortality. The major findings described in this report are: A miniature pressure-sensitive radio transmitter was found to be accurate and precise and, after compensation for water temperature, can be used to determine the depth of tagged-fish to within 0.32 m of the true depth (Chapter 1). Preliminary data from very few fish suggest that depth protects migrating juvenile steelhead from total dissolved gas supersaturation (Chapter 1). As in 1995, few fish had any signs of gas bubble disease, but it appeared that prevalence and severity increased as fish migrated downstream and in response to changing gas supersaturation (Chapter 2). It appeared to gas bubble disease was not a threat to migrating juvenile salmonids when total dissolved gas supersaturation was < 120% (Chapter 2). Laboratory studies suggest that external examinations are appropriate for determining the severity of gas bubble disease in juvenile salmonids (Chapter 3). The authors developed a new method for examining gill arches for intravascular bubbles by clamping the ventral aorta to reduce bleeding when arches were removed (Chapter 3). Despite an outbreak of bacterial kidney disease in the experimental fish, the data indicate that gas bubble disease is a progressive trauma that can be monitored (Chapter 3).
An advanced LIF-PLV system for analysing the hydrodynamics in a laboratory bubble column at higher void fractions
NASA Astrophysics Data System (ADS)
Br—der, D.; Sommerfeld, M.
Bubble columns are widely used in the chemical industry and biotechnology. Flow and turbulence in such an apparatus are induced by the bubble rise, and the bubble behaviour is strongly affected by swarm effects (i.e. the interaction between bubbles). For analysing the bubble swarm behaviour and simultaneously evaluating the flow structure and bubble-induced turbulence, a bubble column of 140 mm diameter and a height of 650 mm or 1,400 mm (initial water level) were considered. The bubble column was aerated with relatively fine bubbles having a mean size between about 0.5 and 4.0 mm. The gas hold-up was varied in the range between 0.5 and 19%. A two-phase pulsed-light velocimetry (PLV) system was developed to evaluate instantaneous flow fields of both rising bubbles and the continuous phase. The measurement of the liquid velocities in the bubble swarm was achieved by adding fluorescing seed particles. Images of bubbles and fluorescing tracer particles were acquired by two CCD cameras. Hence, the images from tracers and bubbles were easily separated by optical interference filters with a bandwidth corresponding to the emitting wavelength of the fluorescing tracer particles and the wavelength of the applied Nd-YAG pulsed laser, respectively. To improve the phase separation of the system, the CCD cameras were additionally placed in a non-perpendicular arrangement with respect to the light sheet. The acquired images were evaluated with the minimum-quadratic-difference algorithm. The potential of this technique for the analysis of bubbly flows with higher void fraction was explored. In order to obtain averaged velocity maps of bubble and fluid within the entire column, about 1,000 image pairs were recorded and evaluated for each phase. In addition, turbulence intensities of the fluid were deduced from the measurements. The turbulence properties were used to characterise bubble-induced turbulence for various bubble mean diameters and gas hold-ups. Moreover, the determination of the average bubble slip velocity within the bubble swarm was possible.
Gas bubble transport and emissions for shallow peat from a northern peatland: The role of pressure changes and peat structure
NASA Astrophysics Data System (ADS)
Chen, Xi; Slater, Lee
Gas bubbles are an important pathway for methane release from peatlands. The mechanisms controlling gas bubble transport and emissions in peat remain uncertain. The effects of hydrostatic pressure and peat structure on the dynamics of gas bubbles in shallow peat were therefore tested in laboratory experiments. A peat monolith was retrieved from a raised bog and maintained in a saturated state. Three distinct layers were identified from noninvasive permittivity measurements supported by soil physical properties (porosity, bulk density). Phase I of the experiment involved monitoring for the accumulation of gas bubbles under steady pressure and temperature conditions. The data showed evidence for gas bubbles being impeded by a shallow semiconfining layer at depths between 10 and 15 cm. Visible gas bubbles observed on the side of the sample box were recorded over time to estimate changes in the vertical distribution of volumetric gas content. Porosity estimates derived using the Complex Refraction Index Model (CRIM) suggest that gas bubbles enlarge the pore space when the exerted pressure is high enough. Phase II involved triggering release of trapped bubbles by repeatedly increasing and decreasing hydrostatic pressure in an oversaturated condition. Comparison of changes in pressure head and methane density in the head space confirmed that the increasing buoyancy force during drops in pressure is more important for triggering ebullition than increasing mobility during increases in pressure. Our findings demonstrate the importance of changes in hydrostatic pressure on bubble size and variations in resistance of the peat fabric in regulating methane releases from peatlands.
Circulation of bubbly magma and gas segregation within tunnels of the potential Yucca Mountain repository
NASA Astrophysics Data System (ADS)
Menand, Thierry; Phillips, Jeremy C.; Sparks, R. Stephen J.
Following an intersection of rising magma with drifts of the potential Yucca Mountain nuclear waste repository, a pathway is likely to be established to the surface with magma flowing for days to weeks and affecting the performance of engineered structures located along or near the flow path. In particular, convective circulation could occur within magma-filled drifts due to the exsolution and segregation of magmatic gas. We investigate gas segregation in a magma-filled drift intersected by a vertical dyke by means of analogue experiments, focusing on the conditions of sustained magma flow. Degassing is simulated by electrolysis, producing micrometric bubbles in viscous mixtures of water and golden syrup, or by aerating golden syrup, producing polydisperse bubbly mixtures with 40% of gas by volume. The presence of exsolved bubbles induces a buoyancy-driven exchange flow between the dyke and the drift that leads to gas segregation. Bubbles segregate from the magma by rising and accumulating as a foam at the top of the drift, coupled with the accumulation of denser degassed magma at the base of the drift. Steady-state influx of bubbly magma from the dyke into the drift is balanced by outward flux of lighter foam and denser degassed magma. The length and time scales of this gas segregation are controlled by the rise of bubbles in the horizontal drift. Steady-state gas segregation would be accomplished within hours to hundreds of years depending on the viscosity of the degassed magma and the average size of exsolved gas bubbles, and the resulting foam would only be a few cm thick. The exchange flux of bubbly magma between the dyke and the drift that is induced by gas segregation ranges from 1 m3 s-1, for the less viscous magmas, to 10-8 m3 s-1, for the most viscous degassed magmas, with associated velocities ranging from 10-1 to 10-9 m s-1 for the same viscosity range. This model of gas segregation also predicts that the relative proportion of erupted degassed magma, that could potentially carry and entrain nuclear waste material towards the surface, would depend on the value of the dyke magma supply rate relative to the value of the gas segregation flux, with violent eruption of gassy as well as degassed magmas at relatively high magma supply rates, and eruption of mainly degassed magma by milder episodic Strombolian explosions at relatively lower supply rates.
Computational modelling of the interaction of shock waves with multiple gas-filled bubbles in a liquid
NASA Astrophysics Data System (ADS)
Betney, M. R.; Tully, B.; Hawker, N. A.; Ventikos, Y.
This study presents a computational investigation of the interactions of a single shock wave with multiple gas-filled bubbles in a liquid medium. This work illustrates how multiple bubbles may be used in shock-bubble interactions to intensify the process on a local level. A high resolution front-tracking approach is used, which enables explicit tracking of the gas-liquid interface. The collapse of two identical bubbles, one placed behind the other is investigated in detail, demonstrating that peak pressures in a two bubble arrangement can exceed those seen in single bubble collapse. Additionally, a parametric investigation into the effect of bubble separation is presented. It is found that the separation distance has a significant effect on both the shape and velocity of the main transverse jet of the second bubble. Extending this analysis to effects of relative bubble size, we show that if the first bubble is sufficiently small relative to the second, it may become entirely entrained in the second bubble main transverse jet. In contrast, if the first bubble is substantially larger than the second, it may offer it significant protection from the incident shock. This protection is utilised in the study of a triangular array of three bubbles, with the central bubble being significantly smaller than the outer bubbles. It is demonstrated that, through shielding of bubbles until later in the collapse process, pressures over five times higher than the maximum pressure observed in the single bubble case may be achieved. This corresponds to a peak pressure that is approximately 40 times more intense than the incident shock wave. This work has applications in a number of different fields, including cavitation erosion, explosives, targeted drug delivery/intensification, and shock wave lithotripsy.
Dissolution without disappearing: multicomponent gas exchange for CO2 bubbles in a microfluidic channel.
Shim, Suin; Wan, Jiandi; Hilgenfeldt, Sascha; Panchal, Prathamesh D; Stone, Howard A
We studied the dissolution dynamics of CO2 gas bubbles in a microfluidic channel, both experimentally and theoretically. In the experiments, spherical CO2 bubbles in a flow of a solution of sodium dodecyl sulfate (SDS) first shrink rapidly before attaining an equilibrium size. In the rapid dissolution regime, the time to obtain a new equilibrium is 30 ms regardless of SDS concentration, and the equilibrium radius achieved varies with the SDS concentration. To explain the lack of complete dissolution, we interpret the results by considering the effects of other gases (O2, N2) that are already dissolved in the aqueous phase, and we develop a multicomponent dissolution model that includes the effect of surface tension and the liquid pressure drop along the channel. Solutions of the model for a stationary gas bubble show good agreement with the experimental results, which lead to our conclusion that the equilibrium regime is obtained by gas exchange between the bubbles and liquid phase. Also, our observations from experiments and model calculations suggest that SDS molecules on the gas-liquid interface form a diffusion barrier, which controls the dissolution behaviour and the eventual equilibrium radius of the bubble. PMID:24874437
Modeling the influence of bubble pressure on grain boundary separation and fission gas release
Pritam Chakraborty; Michael R. Tonks; Giovanni Pastore
Grain boundary (GB) separation as a mechanism for fission gas release (FGR), complementary to gas bubble interlinkage, has been experimentally observed in irradiated light water reactor fuel. However there has been limited effort to develop physics-based models incorporating this mechanism for the analysis of FGR. In this work, a computational study is carried out to investigate GB separation in UO2 fuel under the effect of gas bubble pressure and hydrostatic stress. A non-dimensional stress intensity factor formula is obtained through 2D axisymmetric analyses considering lenticular bubbles and Mode-I crack growth. The obtained functional form can be used in higher length-scale models to estimate the contribution of GB separation to FGR.
A two-compartment convective-diffusion model for slurry bubble column reactors
Degaleesan, S.; Dudukovic, M.P. [Washington Univ., St. Louis, MO (United States); Toseland, B.A.; Bhatt, B.L. [Air Products and Chemicals, Inc., Lehigh Valley, PA (United States)
Synthesis gas can be made from a variety of coal, natural gas, environmentally distressed materials such as petroleum coke and biomass. There are considerable reactor design and scale-up problems associated with synthesis gas conversion technologies which arise due to the special characteristics of these processes. Bubble columns and slurry bubble column reactors (SBCRs), due to their superior heat transfer characteristics, are the contactors of choice for conversion of syngas to fuels and chemicals. The multiphase fluid dynamics in these systems determines the mass and heat transfer and greatly affects reactor volumetric productivity and selectivity. Here the authors show how the recently collected data for liquid velocity, turbulence parameters, and holdup profiles can be used in guiding model development for liquid backmixing and in providing the needed model parameters. Predictions of the two-compartment convective-diffusion model for the residence time distribution of a nonvolatile tracer, which are based on measured liquid recirculation driven by the gas holdup profile and turbulence caused by the rising gas bubbles, are shown to be in good agreement with tracer data. The adaptation of model parameters needed to achieve predictability for industrial tracer data is discussed. The ability of the model to predict the liquid tracer responses at various locations in a SBCR during methanol synthesis is illustrated.
Experiment and Numerical Simulation of Bubble Behavior in Argon Gas Injection into Lead-Bismuth Pool
NASA Astrophysics Data System (ADS)
Yamada, Yumi; Akashi, Toyou; Takahashi, Minoru
In a lead-bismuth alloy (45%Pb-55%Bi) cooled direct contact boiling water fast reactor (PBWFR), steam can be produced by direct contact of feed water with primary Pb-Bi coolant in the upper core plenum, and Pb-Bi coolant can be circulated by buoyancy forces of steam bubbles. As a basic study to investigate the two-phase flow characteristics in the chimneys of PBWFR, a two-dimensional two-phase flow was simulated by injecting argon gas into Pb-Bi pool in a rectangular vessel (400mm in length, 1500mm in height), and bubble behavior were investigated experimentally. Bubble sizes, bubble rising velocities and void fractions were measured using void probes. The experimental conditions are the atmospheric pressure and the flow rate of injection Ar gas is 10, 20, and 30 NL/min. The average of measured bubble rising velocity was about 0.6 m/s. The average chord length was about 7mm. An analysis was performed by two-dimensional and two-fluid model. The experimental results were compared with the analytical results to evaluate the validity of the analytical model. Although large diameter bubbles were observed in the experiment, the drag force model of lower value performed better for simulation of the experimental result.
Evolution of a gas bubble in porous matrix filled by methane hydrate
NASA Astrophysics Data System (ADS)
Tsiberkin, Kirill; Lyubimov, Dmitry; Lyubimova, Tatyana; Zikanov, Oleg
Behavior of a small isolated hydrate-free inclusion (a bubble) within hydrate-bearing porous matrix is studied analytically and numerically. An infinite porous matrix of uniform properties with pores filled by methane hydrates and either water (excessive water situation) or methane gas (excessive gas situation) is considered. A small spherical hydrate-free bubble of radius R0 exists at initial moment within the matrix due to overheating relative to the surrounding medium. There is no continuing heat supply within the bubble, so new hydrate forms on its boundary, and its radius decreases with time. The process is analysed in the framework of the model that takes into account the phase transition and accompanying heat and mass transport processes and assumes spherical symmetry. It is shown that in the case of small (~ 10-2-10-1 m) bubbles, convective fluxes are negligible and the process is fully described by heat conduction and phase change equations. A spherically symmetric Stefan problem for purely conduction-controlled evolution is solved analytically for the case of equilibrium initial temperature and pressure within the bubble. The self-similar solution is verified, with good results, in numerical simulations based on the full filtration and heat transfer model and using the isotherm migration method. Numerical simulations are also conducted for a wide range of cases not amenable to analytical solution. It is found that, except for initial development of an overheated bubble, its radius evolves with time following the self-similar formula: R(t) ( t)1-2 R0-= 1 - tm- , (1) where tm is the life-time of bubble (time of its complete freezing). The analytical solution shows that tm follows 2 tm ~ (R0-?) , (2) where ? is a constant determined by the temperature difference ?T between the bubble's interior and far field. We consider implications for natural hydrate deposits. As an example, for a bubble with R0 = 4 cm and ?T = 0.001 K, we find tm ~ 5.7 ? 106 s (2 months) in a water excess system, and ~ 2.9 ? 107 s (11 months) in a gas excess system. Motion of the bubble is not considered in our study, but it can be estimated that at the typical velocity of buoyancy-driven transport, a small bubble does not move a significant distance over its life-time and, thus, cannot survive filtration through the hydrate stability zone. Work was financially supported by the Civilian Research and Development Foundation (Grant RUP1-2945-PE-09) and the Russian Foundation for Basic Research (Grant 09-01-92505).
MRI-guided gas bubble enhanced ultrasound heating in in vivo rabbit thigh.
Sokka, S D; King, R; Hynynen, K
In this study, we propose a focused ultrasound surgery protocol that induces and then uses gas bubbles at the focus to enhance the ultrasound absorption and ultimately create larger lesions in vivo. MRI and ultrasound visualization and monitoring methods for this heating method are also investigated. Larger lesions created with a carefully monitored single ultrasound exposure could greatly improve the speed of tumour coagulation with focused ultrasound. All experiments were performed under MRI (clinical, 1.5 T) guidance with one of two eight-sector, spherically curved piezoelectric transducers. The transducer, either a 1.1 or 1.7 MHz array, was driven by a multi-channel RF driving system. The transducer was mounted in an MRI-compatible manual positioning system and the rabbit was situated on top of the system. An ultrasound detector ring was fixed with the therapy transducer to monitor gas bubble activity during treatment. Focused ultrasound surgery exposures were delivered to the thighs of seven New Zealand while rabbits. The experimental, gas-bubble-enhanced heating exposures consisted of a high amplitude 300 acoustic watt, half second pulse followed by a 7 W, 14 W or 21 W continuous wave exposure for 19.5 s. The respective control sonications were 20 s exposures of 14 W, 21 W and 28 W. During the exposures, MR thermometry was obtained from the temperature dependency of the proton resonance frequency shift. MRT2-enhanced imaging was used to evaluate the resulting lesions. Specific metrics were used to evaluate the differences between the gas-bubble-enhanced exposures and their respective control sonications: temperatures with respect to time and space, lesion size and shape, and their agreement with thermal dose predictions. The bubble-enhanced exposures showed a faster temperature rise within the first 4 s and higher overall temperatures than the sonications without bubble formation. The spatial temperature maps and the thermal dose maps derived from the MRI thermometry closely correlated with the resulting lesion as examined by T2-weighted imaging. The lesions created with the gas-bubble-enhanced heating exposures were 2-3 times larger by volume, consistently more spherical in shape and closer to the transducer than the control exposures. The study demonstrates that gas bubbles can reliably be used to create significantly larger lesions in vivo. MRI thermometry techniques were successfully used to monitor the thermal effects mediated by the bubble-enhanced exposures. PMID:12587906
M.H. Al-Dahhan; M.P. Dudukovic; L.S. Fan
This report summarizes the accomplishment made during the second year of this cooperative research effort between Washington University, Ohio State University and Air Products and Chemicals. The technical difficulties that were encountered in implementing Computer Automated Radioactive Particle Tracking (CARPT) in high pressure SBCR have been successfully resolved. New strategies for data acquisition and calibration procedure have been implemented. These have been performed as a part of other projects supported by Industrial Consortium and DOE via contract DE-2295PC95051 which are executed in parallel with this grant. CARPT and Computed Tomography (CT) experiments have been performed using air-water-glass beads in 6 inch high pressure stainless steel slurry bubble column reactor at selected conditions. Data processing of this work is in progress. The overall gas holdup and the hydrodynamic parameters are measured by Laser Doppler Anemometry (LDA) in 2 inch slurry bubble column using Norpar 15 that mimic at room temperature the Fischer Tropsch wax at FT reaction conditions of high pressure and temperature. To improve the design and scale-up of bubble column, new correlations have been developed to predict the radial gas holdup and the time averaged axial liquid recirculation velocity profiles in bubble columns.
Acoustic monitoring of gas emissions from the seafloor. Part I: quantifying the volumetric flow of bubbles
NASA Astrophysics Data System (ADS)
Leblond, Isabelle; Scalabrin, Carla; Berger, Laurent
Three decades of continuous ocean exploration have led us to identify subsurface fluid related processes as a key phenomenon in marine earth science research. The number of seep areas located on the seafloor has been constantly increasing with the use of multi-scale imagery techniques. Due to recent advances in transducer technology and computer processing, multibeam echosounders are now commonly used to detect submarine gas seeps escaping from the seafloor into the water column. A growing number of en- route surveys shows that sites of gas emissions escaping from the seafloor are much more numerous than previously thought. Estimating the temporal variability of the gas flow rate and volumes escaping from the seafloor has thus become a challenge of relevant interest which could be addressed by sea-floor continuous acoustic monitoring. Here, we investigate the feasibility of estimating the volumetric flow rates of gas emissions from horizontal backscattered acoustic signals. Different models based on the acoustic backscattering theory of bubbles are presented. The forward volume backscattering strength and the inversion volumetric flow rate solutions were validated with acoustic measurements from artificial gas flow rates generated in controlled sea-water tank experiments. A sensitivity analysis was carried out to investigate the behavior of the 120-kHz forward solution with respect to model input parameters (horizontal distance between transducer and bubble stream, bubble size distribution and ascent rate). The most sensitive parameter was found to be the distance of the bubble stream which can affect the volume backscattering strength by 20 dB within the horizontal range of 0-200 m. Results were used to derive the detection probability of a bubble stream for a given volume backscattering strength threshold according to different bubble flow rates and horizontal distance.
Visualization of gasliquid mass transfer and wake structure of rising bubbles using pH-sensitive PLIF
Stohr, M.
A planar laser-induced fluorescence (PLIF) technique for visualizing gasliquid mass transfer and wake structure of rising gas bubbles is described. The method uses an aqueous solution of the pH-sensitive dye Naphthofluorescein ...
Shear stress induced by a gas bubble pulsating in an ultrasonic field near a wall.
Krasovitski, Boris; Kimmel, Eitan
Some of the effects that therapeutic ultrasound has in medicine and biology may be associated with steady oscillations of gas bubbles in liquid, very close to tissue surface. The bubble oscillations induce on the surface steady shear stress attributed to microstreaming. A mathematical simulation of the problem for both free and capsulated bubbles, known as contrast agents, is presented here. The simulation is based on a solution of Laplace's equation for potential flow and existing models for microstreaming. The solution for potential flow was obtained numerically using a boundary integral method. The solution provides the evolution of the bubble shape, the distribution of the velocity potential on the surface, and the shear stress along the surface. The simulation shows that significant shear stresses develop on the surface when the bubble bounces near the tissue surface. In this case, pressure amplitude of 20 kPa generates maximal steady shear stress of several kilo Pascal. Substantial shear stress on the tissue surface takes place inside a circular zone with a radius about half of the bubble radius. The predicted shear stress is greater than stress that causes hemolysis in blood and several orders of magnitude greater than the physiological stress induced on the vessel wall by the flowing blood. PMID:15344403
Effects of gas bubble production on heat transfer from a volumetrically heated liquid pool
NASA Astrophysics Data System (ADS)
Bull, Geoffrey R.
Aqueous solutions of uranium salts may provide a new supply chain to fill potential shortfalls in the availability of the most common radiopharmaceuticals currently in use worldwide, including Tc99m which is a decay product of Mo99. The fissioning of the uranium in these solutions creates Mo99 but also generates large amounts of hydrogen and oxygen from the radiolysis of the water. When the dissolved gases reach a critical concentration, bubbles will form in the solution. Bubbles in the solution affect both the fission power and the heat transfer out of the solution. As a result, for safety and production calculations, the effects of the bubbles on heat transfer must be understood. A high aspect ratio tank was constructed to simulate a section of an annulus with heat exchangers on the inner and outer steel walls to provide cooling. Temperature measurements via thermocouples inside the tank and along the outside of the steel walls allowed the calculation of overall and local heat transfer coefficients. Different air injection manifolds allowed the exploration of various bubble characteristics and patterns on heat transfer from the pool. The manifold type did not appear to have significant impact on the bubble size distributions in water. However, air injected into solutions of magnesium sulfate resulted in smaller bubble sizes and larger void fractions than those in water at the same injection rates. One dimensional calculations provide heat transfer coefficient values as functions of the superficial gas velocity in the pool.
RESEARCH PAPER Use of a porous membrane for gas bubble removal in microfluidic
Attinger, Daniel
heating (Prakash and Gershenfeld 2007) and piezo actuation (Xu and Attinger 2008). Sometimes unwanted gas pockets can form, accidentally due to priming or cavitation. These bubbles are sometimes useful, e.g., enhancing heat and mass transfer (Gunther et al. 2004; Kreutzer et al. 2005; Betz and Attinger 2010
Numerical simulation of Marangoni convection around gas bubbles in a liquid matrix
Johannes Straub; Johann Betz; Rudi Marek
Transient Marangoni convection under micro and Earth gravity conditions around a gas bubble floating in a liquid filled rectangular box with adiabatic side walls, while the bottom and top walls are maintained at different temperatures, is simulated with a two dimensional model. Employing two numerical methods, a finite difference scheme with explicit time steps and a fully implicit control volume
Liquid circulation and critical gas velocity in slurry bubble column with short size draft tube
Hiromitsu Kojima; Jun Sawai; Hidetoshi Uchino; Takakazu Ichige
Longitudinal solid distribution and liquid circulation were discussed experimentally in slurry bubble column with short size draft tube. Solid distribution along the column axis was well explained by one-dimensional dispersion model. The relation between circulation rate and critical gas velocity for complete suspension was discussed taking into account the mechanism for suspending solid particle in horizontal pipe.
Gas Bubble Disease in Smallmouth Bass and Northern Squawfish from the Snake and Columbia Rivers
Jerry C. Montgomery; C. Dale Becker
In 1975 and 1976, 179 smallmouth bass (Micropterus dolomieui) and 85 northern squawfish (Ptychocheilus oregonensis) were collected by angling from the lower Snake and mid-Columbia rivers, southeastern Washington. All fish were examined externally for gas bubble syndrome. Emboli were found beneath membranes of the opercula, body, and fins of 72% of the smallmouth bass and 84% of the northern squawfish.
Hydrodynamic simulation of methanol synthesis in gasliquid slurry bubble column reactors
Yuanxiang Wu; Dimitri Gidaspow
A transient, two-dimensional hydrodynamic model for the production of methanol from syn-gas in an Air Products\\/DOE LaPorte slurry bubble column reactor was developed. The model predicts downflow of catalyst at the walls and oscillatory particle and gas flow at the center, with a frequency of about 0.7H. The computed temperature variation in the reactor with heat exchangers was only about
Velocity field in isothermal turbulent bubbly gas-liquid flow through a pipe
NASA Astrophysics Data System (ADS)
Velidandla, V.; Putta, S.; Roy, R. P.
Velocity field was measured by laser Doppler velocimetry in isothermal, turbulent bubbly gas-liquid flow through a 26.6 mm inner diameter vertical pipe. The measurements were made about 33 diameters downstream from the pipe entrance, gas injection being just upstream of the entrance. The gas phase radial distribution at the measurement plane exhibited influence of the injection device in that higher gas fraction existed in the central region of the pipe. For comparison, velocity field was also measured in isothermal, turbulent single-phase liquid flow through the same pipe at the same axial plane. Measured were the radial distributions of liquid mean axial and radial velocities, axial and radial turbulent intensities, and axial Reynolds shear stress. The radial distributions of gas bubble mean axial velocity and axial velocity fluctuation intensity were also measured by LDV. A dualsensor fiberoptic probe was used at the same time to measure the radial distributions of gas fraction, bubble mean axial velocity and size slightly downstream of the LDV measurement plane.
The Experimental Study of Dynamics of Scaled Gas-Filled Bubble Collapse in Liquid
NASA Astrophysics Data System (ADS)
Pavlenko, Alexander
The article provides results of analyzing special features of the single-bubble sonoluminescence, developing the special apparatus to investigate this phenomenon on a larger-scale basis. Certain very important effects of high energy density physics, i.e. liquid compressibility, shock-wave formation under the collapse of the gas cavity in liquid, shock-wave focusing in the gas-filled cavity, occurrence of hot dense plasma in the focusing area, and high-temperature radiation yield are observed in this phenomenon. Specificity of the process is conditioned by the ``ideal'' preparation and sphericity of the gas-and-liquid contact boundary what makes the collapse process efficient due to the reduced influence of hydrodynamic instabilities. Results of experimental investigations; results of developing the facilities, description of methods used to register parameters of facilities and the system under consideration; analytical estimates how gas-filled bubbles evolve in liquid with the regard for scale effects; results of preliminary 1-D gas dynamic calculations of the gas bubble evolution are presented. The work supported by ISTC Project #2116.
Helium gas bubble trapped in liquid helium in high magnetic field
Bai, H., E-mail: firstname.lastname@example.com; Hannahs, S. T.; Markiewicz, W. D.; Weijers, H. W. [National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 (United States)
High magnetic field magnets are used widely in the area of the condensed matter physics, material science, chemistry, geochemistry, and biology at the National High Magnetic Field Laboratory. New high field magnets of state-of-the-art are being pursued and developed at the lab, such as the current developing 32?T, 32?mm bore fully superconducting magnet. Liquid Helium (LHe) is used as the coolant for superconducting magnets or samples tested in a high magnetic field. When the magnetic field reaches a relatively high value the boil-off helium gas bubble generated by heat losses in the cryostat can be trapped in the LHe bath in the region where BzdBz/dz is less than negative 2100 T{sup 2}/m, instead of floating up to the top of LHe. Then the magnet or sample in the trapped bubble region may lose efficient cooling. In the development of the 32?T magnet, a prototype Yttrium Barium Copper Oxide coil of 6 double pancakes with an inner diameter of 40?mm and an outer diameter of 140?mm was fabricated and tested in a resistive magnet providing a background field of 15?T. The trapped gas bubble was observed in the tests when the prototype coil was ramped up to 7.5?T at a current of 200?A. This letter reports the test results on the trapped gas bubble and the comparison with the analytical results which shows they are in a good agreement.
Removal of dichloromethane from waste gas streams using a hybrid bubble column/biofilter bioreactor
The performance of a hybrid bubble column/biofilter (HBCB) bioreactor for the removal of dichloromethane (DCM) from waste gas streams was studied in continuous mode for several months. The HBCB bioreactor consisted of two compartments: bubble column bioreactor removing DCM from liquid phase and biofilter removing DCM from gas phase. Effect of inlet DCM concentration on the elimination capacity was examined in the DCM concentration range of 34359 ppm with loading rates ranged from 2.2 to 22.8 g/m3.h and constant total empty bed retention time (EBRT) of 200 s. In the equal loading rates, the elimination capacity and removal efficiency of the biofilter were higher than the corresponding values of the bubble column bioreactor. The maximum elimination capacity of the HBCB bioreactor was determined to be 15.7 g/m3.h occurred in the highest loading rate of 22.8 g/m3.h with removal efficiency of 69%. The overall mineralization portion of the HBCB bioreactor was in the range of 72-79%. The mixed liquor acidic pH especially below 5.5 inhibited microbial activity and decreased the elimination capacity. Inhibitory effect of high ionic strength was initiated in the mixed liquor electrical conductivity of 12.2 mS/cm. This study indicated that the HBCB bioreactor could benefit from advantages of both bubble column and biofilter reactors and could remove DCM from waste gas streams in a better manner. PMID:24406056
Catalytic microtubular jet engines self-propelled by accumulated gas bubbles.
Solovev, Alexander A; Mei, Yongfeng; Bermºdez Ureþa, Esteban; Huang, Gaoshan; Schmidt, Oliver G
Strain-engineered microtubes with an inner catalytic surface serve as self-propelled microjet engines with speeds of up to approximately 2 mm s(-1) (approximately 50 body lengths per second). The motion of the microjets is caused by gas bubbles ejecting from one opening of the tube, and the velocity can be well approximated by the product of the bubble radius and the bubble ejection frequency. Trajectories of various different geometries are well visualized by long microbubble tails. If a magnetic layer is integrated into the wall of the microjet engine, we can control and localize the trajectories by applying external rotating magnetic fields. Fluid (i.e., fuel) pumping through the microtubes is revealed and directly clarifies the working principle of the catalytic microjet engines. PMID:19373828
Direct numerical simulation of single gas bubbles in pure and contaminated liquids
NASA Astrophysics Data System (ADS)
Lakshmanan, Peter; Ehrhard, Peter
Disperse gas bubbles play an important role in many industrial applications. Knowing the rising velocity, the interfacial area, or the critical size for break-up or coalescence in different systems can be crucial for the process design. Hence, knowing the fundamental behaviour of a single bubble appears mandatory for the examination of bubble swarms and for the Euler-Lagrange or Euler--Euler modelling of disperse systems. In the present work a level--set--based volume--tracking method is implemented into the CFD--code OpenFOAM to follow the free interface of a single bubble. The volume-tracking method is coupled with a transport model for surfactants on the interface, including adsorption and desorption processes. The dependency of surface tension on the local surfactant concentration on the interface is modelled by a non-linear (Langmuir) equation of state. Marangoni forces, resulting from surface tension gradients, are included. The rise of a single air bubble (i) in pure water and (ii) in the presence of surfactants of different strengths is simulated. The results show good agreement with available (experimental and theoretical) correlations from literature.
Compositional Discrimination of Decompression and Decomposition Gas Bubbles in Bycaught Seals and Dolphins
Bernaldo de Quirµs, Yara; Seewald, Jeffrey S.; Sylva, Sean P.; Greer, Bill; Niemeyer, Misty; Bogomolni, Andrea L.; Moore, Michael J.
Gas bubbles in marine mammals entangled and drowned in gillnets have been previously described by computed tomography, gross examination and histopathology. The absence of bacteria or autolytic changes in the tissues of those animals suggested that the gas was produced peri- or post-mortem by a fast decompression, probably by quickly hauling animals entangled in the net at depth to the surface. Gas composition analysis and gas scoring are two new diagnostic tools available to distinguish gas embolisms from putrefaction gases. With this goal, these methods have been successfully applied to pathological studies of marine mammals. In this study, we characterized the flux and composition of the gas bubbles from bycaught marine mammals in anchored sink gillnets and bottom otter trawls. We compared these data with marine mammals stranded on Cape Cod, MA, USA. Fresh animals or with moderate decomposition (decomposition scores of 2 and 3) were prioritized. Results showed that bycaught animals presented with significantly higher gas scores than stranded animals. Gas composition analyses indicate that gas was formed by decompression, confirming the decompression hypothesis. PMID:24367623
Prospecting for zones of contaminated ground-water discharge to streams using bottom-sediment gas bubbles
Vroblesky, Don A.; Lorah, Michelle M.
Decomposition of organic-rich bottom sediment in a tidal creek in Maryland results in production of gas bubbles in the bottom sediment during summer and fall. In areas where volatile organic contaminants discharge from ground water, through the bottom sediment, and into the creek, part of the volatile contamination diffuses into the gas bubbles and is released to the atmosphere by ebullition. Collection and analysis of gas bubbles for their volatile organic contaminant content indicate that relative concentrations of the volatile organic contaminants in the gas bubbles are substantially higher in areas where the same contaminants occur in the ground water that discharges to the streams. Analyses of the bubbles located an area of previously unknown ground-water contamination. The method developed for this study consisted of disturbing the bottom sediment to release gas bubbles, and then capturing the bubbles in a polyethylene bag at the water-column surface. The captured gas was transferred either into sealable polyethylene bags for immediate analysis with a photoionization detector or by syringe to glass tubes containing wires coated with an activated-carbon adsorbent. Relative concentrations were determined by mass spectral analysis for chloroform and trichloroethylene.
Gas bubble retention and its effect on waste properties: Retention mechanisms, viscosity, and tensile and shear strengths
Gauglitz, P.A.; Rassat, S.D.; Powell, M.R. [and others
Several of the underground nuclear storage tanks at Hanford have been placed on a flammable gas watch list, because the waste is either known or suspected to generate, store, and episodically release flammable gases. Because retention and episodic release of flammable gases from these tanks containing radioactive waste slurries are critical safety concerns, Pacific Northwest Laboratory (PNL) is studying physical mechanisms and waste properties that contribute to the episodic gas release from these storage tanks. This study is being conducted for Westinghouse Hanford Company as part of the PNL Flammable Gas project. Previous investigations have concluded that gas bubbles are retained by the slurry or sludge that has settled at the bottom of the tanks; however, the mechanisms responsible for the retention of these bubbles are not well understood. Understanding the rheological behavior of the waste, particularly of the settled sludge, is critical to characterizing the tendency of the waste to retain gas bubbles and the dynamics of how these bubbles are released from the waste. The presence of gas bubbles is expected to affect the rheology of the sludge, specifically its viscosity and tensile and shear strengths, but essentially no literature data are available to assess the effect of bubbles. The objectives of this study were to conduct experiments and develop theories to understand better how bubbles are retained by slurries and sludges, to measure the effect of gas bubbles on the viscosity of simulated slurries, and to measure the effect of gas bubbles on the tensile and shear strengths of simulated slurries and sludges. In addition to accomplishing these objectives, this study developed correlations, based on the new experimental data, that can be used in large-scale computations of waste tank physical phenomena.
Generating Singlet Oxygen Bubbles: A New Mechanism for Gas-Liquid Oxidations in Water
Bartusik, Dorota; Aebisher, David; Ghafari, BiBi
Laser-coupled microphotoreactors were developed to bubble singlet oxygen [1O2 (1?g)] into an aqueous solution containing an oxidizable compound. The reactors consisted of custom-modified SMA fiber-optic receptacles loaded with 150-?m silicon phthalocyanine glass sensitizer particles, where the particles were isolated from direct contact with water by a membrane adhesively bonded to the bottom of each device. A tube fed O2 gas to the reactor chambers. In the presence of O2, singlet oxygen was generated by illuminating the sensitizer particles with 669-nm light from an optical fiber coupled to the top of the reactor. The generated 1O2 was transported through the membrane by the O2 stream and formed bubbles in solution. In solution, singlet oxygen reacted with probe compounds (either 9,10-anthracene dipropionate dianion, trans-2-methyl-2-pentanoate anion, N-benzoyl-D,L-methionine, and N-acetyl-D,L-methionine) to give oxidized products in two stages. The early stage was rapid and showed that 1O2 transfer occurred via bubbles mainly in the bulk water solution. The later stage was slow, it arose only from 1O2-probe molecule contact at the gas/liquid interface. A mechanism is proposed that involves 1O2 mass transfer and solvation, where smaller bubbles provide better penetration of 1O2 into the flowing stream due to higher surface-to-volume contact between the probe molecules and 1O2. PMID:22260325
Gas Bubble Trauma Monitoring and Research of Juvenile Salmonids, 1994-1995 Progress Report.
Hans, Karen M.
This report describes laboratory and field monitoring studies of gas bubble trauma (GBT) in migrating juvenile salmonids in the Snake and Columbia rivers. The first chapter describes laboratory studies of the progression of GBT signs leading to mortality and the use of the signs for GBT assessment. The progression and severity of GBT signs in juvenile salmonids exposed to different levels of total dissolved gas (TDG) and temperatures was assessed and quantified. Next, the prevalence, severity, and individual variation of GBT signs was evaluated to attempt to relate them to mortality. Finally, methods for gill examination in fish exposed to high TDG were developed and evaluated. Primary findings were: (1) no single sign of GBT was clearly correlated with mortality, but many GBT signs progressively worsened; (2) both prevalence and severity of GBT signs in several tissues is necessary; (3) bubbles in the lateral line were the earliest sign of GBT, showed progressive worsening, and had low individual variation but may develop poorly during chronic exposures; (4) fin bubbles had high prevalence, progressively worsened, and may be a persistent sign of GBT; and (5) gill bubbles appear to be the proximate cause of death but may only be relevant at high TDG levels and are difficult to examine. Chapter Two describes monitoring results of juvenile salmonids for signs of GBT. Emigrating fish were collected and examined for bubbles in fins and lateral lines. Preliminary findings were: (1) few fish had signs of GBT, but prevalence and severity appeared to increase as fish migrated downstream; (2) there was no apparent correlation between GBT signs in the fins, lateral line, or gills; (3) prevalence and severity of GBT was suggestive of long-term, non-lethal exposure to relatively low level gas supersaturated water; and (4) it appeared that GBT was not a threat to migrating juvenile salmonids. 24 refs., 26 figs., 3 tabs.
Finite-sized gas bubble motion in a blood vessel: Non-Newtonian effects
NASA Astrophysics Data System (ADS)
Mukundakrishnan, Karthik; Ayyaswamy, Portonovo S.; Eckmann, David M.
We have numerically investigated the axisymmetric motion of a finite-sized nearly occluding air bubble through a shear-thinning Casson fluid flowing in blood vessels of circular cross section. The numerical solution entails solving a two-layer fluid modela cell-free layer and a non-Newtonian core together with the gas bubble. This problem is of interest to the field of rheology and for gas embolism studies in health sciences. The numerical method is based on a modified front-tracking method. The viscosity expression in the Casson model for blood (bulk fluid) includes the hematocrit [the volume fraction of red blood cells (RBCs)] as an explicit parameter. Three different flow Reynolds numbers, Reapp=?lUmaxd/?app , in the neighborhood of 0.2, 2, and 200 are investigated. Here, ?l is the density of blood, Umax is the centerline velocity of the inlet Casson profile, d is the diameter of the vessel, and ?app is the apparent viscosity of whole blood. Three different hematocrits have also been considered: 0.45, 0.4, and 0.335. The vessel sizes considered correspond to small arteries, and small and large arterioles in normal humans. The degree of bubble occlusion is characterized by the ratio of bubble to vessel radius (aspect ratio), ? , in the range 0.9???1.05 . For arteriolar flow, where relevant, the Fahraeus-Lindqvist effects are taken into account. Both horizontal and vertical vessel geometries have been investigated. Many significant insights are revealed by our study: (i) bubble motion causes large temporal and spatial gradients of shear stress at the endothelial cell (EC) surface lining the blood vessel wall as the bubble approaches the cell, moves over it, and passes it by; (ii) rapid reversals occur in the sign of the shear stress (+ ? - ? +) imparted to the cell surface during bubble motion; (iii) large shear stress gradients together with sign reversals are ascribable to the development of a recirculation vortex at the rear of the bubble; (iv) computed magnitudes of shear stress gradients coupled with their sign reversals may correspond to levels that cause injury to the cell by membrane disruption through impulsive compression and stretching; and (v) for the vessel sizes and flow rates investigated, gravitational effects are negligible.
Finite-sized gas bubble motion in a blood vessel: Non-Newtonian effects
Mukundakrishnan, Karthik; Ayyaswamy, Portonovo S.; Eckmann, David M.
We have numerically investigated the axisymmetric motion of a finite-sized nearly occluding air bubble through a shear-thinning Casson fluid flowing in blood vessels of circular cross section. The numerical solution entails solving a two-layer fluid modela cell-free layer and a non-Newtonian core together with the gas bubble. This problem is of interest to the field of rheology and for gas embolism studies in health sciences. The numerical method is based on a modified front-tracking method. The viscosity expression in the Casson model for blood (bulk fluid) includes the hematocrit [the volume fraction of red blood cells (RBCs)] as an explicit parameter. Three different flow Reynolds numbers, Reapp=?lUmaxd/?app, in the neighborhood of 0.2, 2, and 200 are investigated. Here, ?l is the density of blood, Umax is the centerline velocity of the inlet Casson profile, d is the diameter of the vessel, and ?app is the apparent viscosity of whole blood. Three different hematocrits have also been considered: 0.45, 0.4, and 0.335. The vessel sizes considered correspond to small arteries, and small and large arterioles in normal humans. The degree of bubble occlusion is characterized by the ratio of bubble to vessel radius (aspect ratio), ?, in the range 0.9???1.05. For arteriolar flow, where relevant, the Fahraeus-Lindqvist effects are taken into account. Both horizontal and vertical vessel geometries have been investigated. Many significant insights are revealed by our study: (i) bubble motion causes large temporal and spatial gradients of shear stress at the endothelial cell (EC) surface lining the blood vessel wall as the bubble approaches the cell, moves over it, and passes it by; (ii) rapid reversals occur in the sign of the shear stress (+ ? ? ? +) imparted to the cell surface during bubble motion; (iii) large shear stress gradients together with sign reversals are ascribable to the development of a recirculation vortex at the rear of the bubble; (iv) computed magnitudes of shear stress gradients coupled with their sign reversals may correspond to levels that cause injury to the cell by membrane disruption through impulsive compression and stretching; and (v) for the vessel sizes and flow rates investigated, gravitational effects are negligible. PMID:18851139
Finite-sized gas bubble motion in a blood vessel: non-Newtonian effects.
Mukundakrishnan, Karthik; Ayyaswamy, Portonovo S; Eckmann, David M
We have numerically investigated the axisymmetric motion of a finite-sized nearly occluding air bubble through a shear-thinning Casson fluid flowing in blood vessels of circular cross section. The numerical solution entails solving a two-layer fluid model--a cell-free layer and a non-Newtonian core together with the gas bubble. This problem is of interest to the field of rheology and for gas embolism studies in health sciences. The numerical method is based on a modified front-tracking method. The viscosity expression in the Casson model for blood (bulk fluid) includes the hematocrit [the volume fraction of red blood cells (RBCs)] as an explicit parameter. Three different flow Reynolds numbers, Reapp=rholUmaxdmicroapp , in the neighborhood of 0.2, 2, and 200 are investigated. Here, rhol is the density of blood, Umax is the centerline velocity of the inlet Casson profile, d is the diameter of the vessel, and microapp is the apparent viscosity of whole blood. Three different hematocrits have also been considered: 0.45, 0.4, and 0.335. The vessel sizes considered correspond to small arteries, and small and large arterioles in normal humans. The degree of bubble occlusion is characterized by the ratio of bubble to vessel radius (aspect ratio), lambda , in the range 0.9< or =lambda< or =1.05 . For arteriolar flow, where relevant, the Fahraeus-Lindqvist effects are taken into account. Both horizontal and vertical vessel geometries have been investigated. Many significant insights are revealed by our study: (i) bubble motion causes large temporal and spatial gradients of shear stress at the "endothelial cell" (EC) surface lining the blood vessel wall as the bubble approaches the cell, moves over it, and passes it by; (ii) rapid reversals occur in the sign of the shear stress (+ --> - --> +) imparted to the cell surface during bubble motion; (iii) large shear stress gradients together with sign reversals are ascribable to the development of a recirculation vortex at the rear of the bubble; (iv) computed magnitudes of shear stress gradients coupled with their sign reversals may correspond to levels that cause injury to the cell by membrane disruption through impulsive compression and stretching; and (v) for the vessel sizes and flow rates investigated, gravitational effects are negligible. PMID:18851139
Gas bubbles in seals, dolphins, and porpoises entangled and drowned at depth in gillnets.
Moore, M J; Bogomolni, A L; Dennison, S E; Early, G; Garner, M M; Hayward, B A; Lentell, B J; Rotstein, D S
Gas bubbles were found in 15 of 23 gillnet-drowned bycaught harp (Pagophilus groenlandicus), harbor (Phoca vitulina) and gray (Halichoerus grypus) seals, common (Delphinus delphis) and white-sided (Lagenorhyncus acutus) dolphins, and harbor porpoises (Phocaena phocaena) but in only 1 of 41 stranded marine mammals. Cases with minimal scavenging and bloating were chilled as practical and necropsied within 24 to 72 hours of collection. Bubbles were commonly visible grossly and histologically in bycaught cases. Affected tissues included lung, liver, heart, brain, skeletal muscle, gonad, lymph nodes, blood, intestine, pancreas, spleen, and eye. Computed tomography performed on 4 animals also identified gas bubbles in various tissues. Mean +/- SD net lead line depths (m) were 92 +/- 44 and ascent rates (ms(-1)) 0.3 +/- 0.2 for affected animals and 76 +/- 33 and 0.2 +/- 0.1, respectively, for unaffected animals. The relatively good carcass condition of these cases, comparable to 2 stranded cases that showed no gas formation on computed tomography (even after 3 days of refrigeration in one case), along with the histologic absence of bacteria and autolytic changes, indicate that peri- or postmortem phase change of supersaturated blood and tissues is most likely. Studies have suggested that under some circumstances, diving mammals are routinely supersaturated and that these mammals presumably manage gas exchange and decompression anatomically and behaviorally. This study provides a unique illustration of such supersaturated tissues. We suggest that greater attention be paid to the radiology and pathology of bycatch mortality as a possible model to better understand gas bubble disease in marine mammals. PMID:19176498
The Holdup Measurement System II (HMSII)
Smith, S.E.; Gibson, J.S. [Oak Ridge Y-12 Plant, TN (United States); Halbig, J.K.; Klosterbuer, S.F.; Russo, P.A.; Sprinkle, J.K. Jr. [Los Alamos National Lab., NM (United States)
A project is in progress that addresses two of the problems with existing holdup measurement technology: the need for compact instrumentation and a more efficient means of reducing the massive amounts of data to quantities of Special Nuclear Materials (SNM). The approach taken by the project utilizes the Miniature Modular MultiChannel Analyzer (M{sup 3}CA), a complete and truly portable gamma-ray spectroscopy system, under development at Los Alamos National Laboratory. The hardware is then integrated and automated by the Holdup Measurement System II (HMSII) software being developed by the Oak Ridge Y-12 Plant. Together they provide the hardware components, measurement control in the field, automated data acquisition, data storage and manipulation which simplify holdup measurements.
Changes in Gas Bubble Disease Signs for Migrating Juvenile Salmonids Experimentally Exposed to Supersaturated Gasses, 1996-1997 Progress Report.
Absolon, Randall F.
This study was designed to answer the question of whether gas bubble disease (GBD) signs change as a result of the hydrostatic conditions juvenile salmonids encounter when they enter the turbine intake of hydroelectric projects during their downstream migration.
Blowing bubbles or smoking pot. [Natural gas availability
W. J. Jr
Updated data showing capacity, demand, and production of natural gas and comparisons of actual versus reported deliverability explore the reasons why producing rates during periods when demand cannot be fully met do not represent true delivery capacity, and contrasts the opinions of experts on the size and durability of US reserves. The author concludes that adequate reserves and deliverability of
Proteomics of Juvenile Senegal Sole ( Solea senegalensis ) Affected by Gas Bubble Disease in Hyperoxygenated Ponds
E. Salas-Leiton; B. CÃnovas-Conesa; R. Zerolo; J. Lµpez-Barea; J. P. Caþavate; J. Alhama
Solea senegalensis is a commercial flat fish traditionally farmed in earth ponds in coastal wetlands that might also become important to more\\u000a intensive aquaculture. Gas bubble disease (GBD) is a potential risk for outdoor fish farming, particularly in certain periods\\u000a of the year, related to improper management leading to macroalgae blooms. Physical-chemical conditions inducing hyperoxia,\\u000a including radiation, temperature, and high
Warm Pressurant Gas Effects on the Bubble Point Pressure for Cryogenic LADs
NASA Technical Reports Server (NTRS)
Hartwig, Jason W.; McQuillen, John B.; Chato, David J.
This paper presents experimental results for the liquid hydrogen and nitrogen bubble point tests using warm pressurant gases conducted at the NASA Glenn Research Center. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device (LAD). Three fine mesh screen samples (325x2300, 450x2750, 510x3600) were tested in liquid hydrogen and liquid nitrogen using cold and warm non-condensable (gaseous helium) and condensable (gaseous hydrogen or nitrogen) pressurization schemes. Gases were conditioned from 0K 90K above the liquid temperature. Results clearly indicate degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over non-condensable pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.
Warm Pressurant Gas Effects on the Static Bubble Point Pressure for Cryogenic LADs
NASA Technical Reports Server (NTRS)
Hartwig, Jason W.; McQuillen, John; Chato, Daniel J.
This paper presents experimental results for the liquid hydrogen and nitrogen bubble point tests using warm pressurant gases conducted at the NASA Glenn Research Center. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device (LAD). Three fine mesh screen samples (325x2300, 450x2750, 510x3600) were tested in liquid hydrogen and liquid nitrogen using cold and warm non-condensable (gaseous helium) and condensable (gaseous hydrogen or nitrogen) pressurization schemes. Gases were conditioned from 0K - 90K above the liquid temperature. Results clearly indicate degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over non-condensable pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.
Shock-induced collapse of a gas bubble in shockwave lithotripsy
Johnsen, Eric; Colonius, Tim
The shock-induced collapse of a pre-existing nucleus near a solid surface in the focal region of a lithotripter is investigated. The entire flow field of the collapse of a single gas bubble subjected to a lithotripter pulse is simulated using a high-order accurate shock- and interface-capturing scheme, and the wall pressure is considered as an indication of potential damage. Results from the computations show the same qualitative behavior as that observed in experiments: a re-entrant jet forms in the direction of propagation of the pulse and penetrates the bubble during collapse, ultimately hitting the distal side and generating a water-hammer shock. As a result of the propagation of this wave, wall pressures on the order of 1 GPa may be achieved for bubbles collapsing close to the wall. The wall pressure decreases with initial stand-off distance and pulse width and increases with pulse amplitude. For the stand-off distances considered in the present work, the wall pressure due to bubble collapse is larger than that due to the incoming shockwave; the region over which this holds may extend to ten initial radii. The present results indicate that shock-induced collapse is a mechanism with high potential for damage in shockwave lithotripsy. PMID:19062841
Lateral line pore diameters correlate with the development of gas bubble trauma signs in several Columbia River fishes
Morris, R.G.; Beeman, J.W.; VanderKooi, S.P.; Maule, A.G.
Gas bubble trauma (GBT) caused by gas supersaturation of river water continues to be a problem in the Columbia River Basin. A common indicator of GBT is the percent of the lateral line occluded with gas bubbles; however, this effect has never been examined in relation to lateral line morphology. The effects of 115, 125 and 130% total dissolved gas levels were evaluated on five fish species common to the upper Columbia River. Trunk lateral line pore diameters differed significantly (Plargescale sucker>northern pikeminnow???chinook salmon???redside shiner). At all supersaturation levels evaluated, percent of lateral line occlusion exhibited an inverse correlation to pore size but was not generally related to total dissolved gas level or time of exposure. This study suggests that the differences in lateral line pore diameters between species should be considered when using lateral line occlusion as an indicator of gas bubble trauma. ?? 2003 Elsevier Science Inc. All rights reserved.
Hydrodynamic models for slurry bubble column reactors. Seventh technical progress report, January--March 1996
Gidaspow, D.
The objective of this investigation is to convert our ``learning gas solid-liquid`` fluidization model into a predictive design model. The IIT hydrodynamic model computes the phase velocities and the volume fractions of gas, liquid and particulate phase. Model verification involves a comparison of these computed velocities and volume fractions to experimental values. A hydrodynamic model for multiphase flows, based on the principles of mass, momentum and energy conservation for each phase, was developed and applied to model gas-liquid, gas-liquid-solid fluidization and gas-solid-solid separation. To simulate the industrial slurry bubble column reactors, a computer program based on the hydrodynamic model was written with modules for chemical reactions (e.g. the synthesis of methanol), phase changes and heat exchangers. In the simulations of gas-liquid two phases flow system, the gas hold-ups, computed with a variety of operating conditions such as temperature, pressure, gas and liquid velocities, agree well with the measurements obtained at Air Products` pilot plant. The hydrodynamic model has more flexible features than the previous empirical correlations in predicting the gas hold-up of gas-liquid two-phase flow systems. In the simulations of gas-liquid-solid bubble column reactors with and without slurry circulation, the code computes volume fractions, temperatures and velocity distributions for the gas, the liquid and the solid phases, as well as concentration distributions for the species (CO, H{sub 2}, CH{sub 3}0H, ... ), after startup from a certain initial state. A kinetic theory approach is used to compute a solid viscosity due to particle collisions. Solid motion and gas-liquid-solid mixing are observed on a color PCSHOW movie made from computed time series data. The steady state and time average catalyst concentration profiles, the slurry height and the rates of methanol production agree well with the measurements obtained at an Air Products` pilot plant.
Feasibility study of using microfluidic platforms for visualizing bubble flows in electrolyzer gas diffusion layers
NASA Astrophysics Data System (ADS)
Arbabi, F.; Kalantarian, A.; Abouatallah, R.; Wang, R.; Wallace, J. S.; Bazylak, A.
In this study, microfluidic platforms were used to visualize air bubble transport in two-dimensional (2D) representations of gas diffusion layers (GDLs) to gain insight into how the geometric features of the GDL impact multiphase flow in polymer electrolyte membrane (PEM) electrolyzers. Two-dimensional porous networks were designed using volumetric pore space information, including average porosity and average throat size obtained from micro-computed tomography (micro CT) visualizations. Microfluidic chips were fabricated to represent felt, sintered powder, and foam GDLs and used to simulate the transfer of oxygen bubbles generated at the catalyst layer, through the GDL towards the flow channels of a PEM electrolyzer. The results of this work indicate that the use of microfluidic platforms for evaluating PEM electrolyzer GDLs is highly promising.
The Effect of Viscosity on the Spherical Stability of Oscillating Gas Bubbles
NASA Technical Reports Server (NTRS)
Hao, Y.; Prosperetti, A.
Gas bubbles driven in radial oscillations are subject to an instability of the spherical shape that is opposed by surface tension and viscosity. An exact linear formulation for the study of the phenomenon has been available for many years, but its complexity has discouraged a detailed investigation. With the recent theory of sonoluminescence of Lohse and co-workers, there has been a renewed interest in the problem and new data have become available. This paper presents a numerical method for the solution of the pertinent equations and compares the theory with these new data. The coupling of the strong nonlinearity of the bubble radial oscillations with the parametric mechanism of the surface instability results in a very complex structure for the stability boundary. Nevertheless, a good agreement between theory and data is found. A comparison with earlier approximate models is also made.
Acoustic emission associated with the bursting of a gas bubble at the free surface of a non-newtonian fluid
Thibaut Divoux; ValÕrie Vidal; Francisco Melo; Jean-Christophe GÕminard
We report experimental measurements of the acoustic emission associated with the bursting of a gas bubble at the free surface of a non-newtonian fluid. On account of the viscoelastic properties of the fluid, the bubble is generally elongated. The associated frequency and duration of the acoustic signal are discussed with regard to the shape of the bubble and successfully accounted for by a simple linear model. The acoustic energy exhibits a high sensitivity to the dynamics of the thin film bursting, which demonstrates that, in practice, it is barely possible to deduce from the acoustic measurements the total amount of energy released by the event. Our experimental findings provide clues for the understanding of the signals from either volcanoes or foams, where one observes respectively, the bursting of giant bubbles at the free surface of lava and bubble bursting avalanches.
Free gas bubbles in the hydrate stability zone: evidence from CT investigation under in situ conditions
NASA Astrophysics Data System (ADS)
Abegg, F.; Freitag, J.; Bohrmann, G.; Brueckmann, W.; Eisenhauer, A.; Amann, H.; Hohnberg, H.-J.
Determination of the internal structures and the fabric of natural marine gas hydrate as well as its distribution in shallow subseafloor depth was restricted because of dissociation during recovery. Investigation under in situ conditions becomes possible with a pressure coring device. The newly developed MultiAutoclaveCorer (MAC) can take up to four cores which are housed in a pressure vessel called LabTransferChamber (LTC), which is compatible with CT imaging technology. During a video-guided deployment on Hydrate Ridge, a well known near-surface gas hydrate-rich environment, two LTCs were filled and recovered under pressure. CT imaging was performed four days after retrieval in a medical clinic in Palo Alto/Ca., a second round was run 2 months later in Kiel/Germany, still under pressure. The same type of scanner was used for both rounds of imaging. The function and the pressure preserving capability of the MAC was confirmed. Although only 0.8 m apart, both cores showed different gas hydrate contents, varying between a maximum of 5 vol-% in LTC 3 and 48 vol-% in LTC 4, documenting the high variability of gas hydrate occurrences in near-surface sediments. The uppermost layer of gas hydrate was observed 0.1 m below the seafloor. The high gas hydrate content in LTC 4 is concentrated in a horizon between 0.28 and 0.32 m subseafloor depth. Within this hoizon a significant quantity of bubbles was detected with a free gas content of up to 2.4 vol-%. Bubble sizes reach a maximum of 1.8 x 10-2 m in either x, y or z direction. Integrating across the mentioned core interval, the gas hydrate content is 19 vol-% and the free gas content is 0.8 vol-%. Assuming several simplifications, the normalised calculated methane volume of the gas hydrate is 9.15 x 10-3 m^3 and the amount of methane in the bubbles is 1.49 x 10-4 m^3.
M.H. Al-Dahhan; L.S. Fan; M.P. Dudukovic
This report summarizes the accomplishment made during the third year of this cooperative research effort between Washington University, Ohio State University and Air Products and Chemicals. Data processing of the performed Computer Automated Radioactive Particle Tracking (CARPT) experiments in 6 inch column using air-water-glass beads (150 {micro}m) system has been completed. Experimental investigation of time averaged three phases distribution in air-Therminol LT-glass beads (150 {micro}m) system in 6 inch column has been executed. Data processing and analysis of all the performed Computed Tomography (CT) experiments have been completed, using the newly proposed CT/Overall gas holdup methodology. The hydrodynamics of air-Norpar 15-glass beads (150 {micro}m) have been investigated in 2 inch slurry bubble column using Dynamic Gas Disengagement (DGD), Pressure Drop fluctuations, and Fiber Optic Probe. To improve the design and scale-up of bubble column reactors, a correlation for overall gas holdup has been proposed based on Artificial Neural Network and Dimensional Analysis.
Periodic Orbit Theory Applied to a Chaotically Oscillating Gas Bubble in Water G. Simon 1 , P. Cvitanovi c 2 , M. T. Levinsen 3 , I. Csabai 4 , and
Levinsen, Mogens T.
. As a result the gas inside the bubble compresses and heats up to the extent that light emission occurs [4 model in the context of acoustic cavitation [14] and showed that the radial oscillations of a gas bubble by the assumptions of ideal gas law, absence of heat transfer, and negligence of surface tension e#11;ects. One
A Study of Vertical Gas Jets in a Bubbling Fluidized Bed
Steven Ceccio; Jennifer Curtis
A detailed experimental study of a vertical gas jet impinging a fluidized bed of particles has been conducted with the help of Laser Doppler Velocimetry measurements. Mean and fluctuating velocity profiles of the two phases have been presented and analyzed for different fluidization states of the emulsion. The results of this work would be greatly helpful in understanding the complex two-phase mixing phenomenon that occurs in bubbling beds, such as in coal and biomass gasification, and also in building more fundamental gas-solid Eulerian/Lagrangian models which can be incorporated into existing CFD codes. Relevant simulations to supplement the experimental findings have also been conducted using the Department of Energyã??s open source code MFIX. The goal of these simulations was two-fold. One was to check the two-dimensional nature of the experimental results. The other was an attempt to improve the existing dense phase Eulerian framework through validation with the experimental results. In particular the sensitivity of existing frictional models in predicting the flow was investigated. The simulation results provide insight on wall-bounded turbulent jets and the effect frictional models have on gas-solid bubbling flows. Additionally, some empirical minimum fluidization correlations were validated for non-spherical particles with the idea of extending the present study to non-spherical particles which are more common in industries.
Noble gas dependence of single-bubble sonoluminescence in phosphoric acid
NASA Astrophysics Data System (ADS)
Faraji, Mehdi; Moshaii, Ahmad
Single-bubble sonoluminescence (SL) from a concentrated solution of phosphoric acid doped with various noble gases has been studied using a hydrochemical model. The results indicate that in agreement with experiment, the SL temperature increases with the atomic mass of the noble gases. Also, both the temperature and the intensity of SL are remarkably higher for lower partial pressures of a noble gas. Our calculations show that the maximum acquirable SL intensity from phosphoric acid is considerably greater than that of water. This mainly originates from the lower vapor pressure and the higher viscosity of phosphoric acid relative to water making the instability mechanisms completely different for these liquids.
Coal gasification by CO 2 gas bubbling in molten salt for solar\\/fossil energy hybridization
Jun Matsunami; Shinya Yoshida; Yoshinori Oku; Osamu Yokota; Yutaka Tamaura; Mitsunobu Kitamura
Coal gasification with CO2 (the Boudouard reaction: C+CO2=2CO, ?rH¯=169.2 kJ\\/mol at 1150 K), which can be applied to a solar thermochemical process to convert concentrated solar heat into chemical energy, was conducted in the molten salt medium (eutectic mixture of Na2CO3 and K2CO3, weight ratio=1\\/1) to provide thermal storage. When CO2 gas was bubbled through the molten salt, higher reaction
Method for gas bubble and void control and removal from metals
Van Siclen, Clinton D. (Idaho Falls, ID); Wright, Richard N. (Idaho Falls, ID)
A method for enhancing the diffusion of gas bubbles or voids attached to impurity precipitates, and biasing their direction of migration out of the host metal (or metal alloy) by applying a temperature gradient across the host metal (or metal alloy). In the preferred embodiment of the present invention, the impurity metal is insoluble in the host metal and has a melting point lower than the melting point of the host material. Also, preferably the impurity metal is lead or indium and the host metal is aluminum or a metal alloy.
Method for gas bubble and void control and removal from metals
Siclen, C.D. Van; Wright, R.N.
A method is described for enhancing the diffusion of gas bubbles or voids attached to impurity precipitates, and biasing their direction of migration out of the host metal (or metal alloy) by applying a temperature gradient across the host metal (or metal alloy). In the preferred embodiment of the present invention, the impurity metal is insoluble in the host metal and has a melting point lower than the melting point of the host material. Also, preferably the impurity metal is lead or indium and the host metal is aluminum or a metal alloy. 2 figs.
Gas Bubble Disease in the Brain of a Living California Sea Lion (Zalophus californianus)
Van Bonn, William; Dennison, Sophie; Cook, Peter; Fahlman, Andreas
A yearling California sea lion (Zalophus californianus) was admitted into rehabilitation with signs of cerebellar pathology. Diagnostic imaging that included radiography and magnetic resonance imaging (MRI) demonstrated space-occupying lesions predominantly in the cerebellum that were filled partially by CSF-like fluid and partially by gas, and cerebral lesions that were fluid filled. Over a maximum period of 4?months, the brain lesions reduced in size and the gas resorbed and was replaced by CSF-like fluid. In humans, the cerebellum is known to be essential for automating practiced movement patterns (e.g., learning to touch-type), also known as procedural learning or the consolidation of motor memory. To test the animal in this study for motor memory deficits, an alternation task in a two-choice maze was utilized. The sea lion performed poorly similar to another case of pneumocerebellum previously reported, and contrary to data acquired from a group of sea lions with specific hippocampal injury. The learning deficits were attributed to the cerebellar injury. These data provide important insight both to the clinical presentation and behavioral observations of cerebellar injury in sea lions, as well as providing an initial model for long-term outcome following cerebellar injury. The specific etiology of the gas could not be determined. The live status of the patient with recovery suggests that the most likely etiologies for the gas are either de novo formation or air emboli secondary to trauma. A small air gun pellet was present within and was removed from soft tissues adjacent to the tympanic bulla. While no evidence to support the pellet striking bone was found, altered dive pattern associated with this human interaction may have provided the opportunity for gas bubble formation to occur. The similarity in distribution of the gas bubble related lesions in this case compared with another previously published case of pneumocerebellum suggests that preferential perfusion of the brain, and more specifically the cerebellum, may occur during diving events. PMID:23372553
Review of Monitoring Plans for Gas Bubble Disease Signs and Gas Supersaturation Levels on the Columbia and Snake Rivers.
Fidler, Larry; Elston, Ralph; Colt, John
Montgomery Watson was retained by the Bonneville Power Administration to evaluate the monitoring program for gas bubble disease signs and dissolved gas supersaturation levels on the Columbia and Snake rivers. The results of this evaluation will provide the basis for improving protocols and procedures for future monitoring efforts. Key study team members were Dr. John Colt, Dr. Larry Fidler, and Dr. Ralph Elston. On the week of June 6 through 10, 1994 the study team visited eight monitoring sites (smolt, adult, and resident fish) on the Columbia and Snake rivers. Additional protocol evaluations were conducted at the Willard Field Station (National Biological Survey) and Pacific Northwest Laboratories at Richland (Battelle). On June 13 and 14, 1994, the study team visited the North Pacific Division office of the U.S. Corps of Engineers and the Fish Passage Center to collect additional information and data on the monitoring programs. Considering the speed at which the Gas Bubble Trauma Monitoring Program was implemented this year, the Fish Passage Center and cooperating Federal, State, and Tribal Agencies have been doing an incredible job. Thirty-one specific recommendations are presented in this report and are summarized in Section 14.
Clostridium perfringens septicemia in a long-beaked common dolphin Delphinus capensis: an etiology of gas bubble accumulation in cetaceans.
Danil, Kerri; St Leger, Judy A; Dennison, Sophie; Bernaldo de Quirµs, Yara; Scadeng, Miriam; Nilson, Erika; Beaulieu, Nicole
An adult female long-beaked common dolphin Delphinus capensis live-stranded in La Jolla, California, USA, on July 30, 2012 and subsequently died on the beach. Computed tomography and magnetic resonance imaging revealed gas bubble accumulation in the vasculature, organ parenchyma, mandibular fat pads, and subdermal sheath as well as a gas-filled cavity within the liver, mild caudal abdominal effusion, and fluid in the uterus. Gross examination confirmed these findings and also identified mild ulcerations on the palate, ventral skin, and flukes, uterine necrosis, and multifocal parenchymal cavitations in the brain. Histological review demonstrated necrosis and round clear spaces interpreted as gas bubbles with associated bacterial rods within the brain, liver, spleen, and lymph nodes. Anaerobic cultures of the lung, spleen, liver, bone marrow, and abdominal fluid yielded Clostridium perfringens, which was further identified as type A via a multiplex PCR assay. The gas composition of sampled bubbles was typical of putrefaction gases, which is consistent with the by-products of C. perfringens, a gas-producing bacterium. Gas bubble formation in marine mammals due to barotrauma, and peri- or postmortem off-gassing of supersaturated tissues and blood has been previously described. This case study concluded that a systemic infection of C. perfringens likely resulted in production of gas and toxins, causing tissue necrosis. PMID:25320031
The effects of total dissolved gas on chum salmon fry survival, growth, gas bubble disease, and seawater tolerance
Geist, David R.; Linley, Timothy J.; Cullinan, Valerie I.; Deng, Zhiqun
Chum salmon Oncorhynchus keta alevin developing in gravel habitats downstream of Bonneville Dam on the Columbia River are exposed to elevated levels of total dissolved gas (TDG) when water is spilled at the dam to move migrating salmon smolts downstream to the Pacific Ocean. Current water quality criteria for the management of dissolved gas in dam tailwaters were developed primarily to protect salmonid smolts and are assumed to be protective of alevin if adequate depth compensation is provided. We studied whether chum salmon alevin exposed to six levels of dissolved gas ranging from 100% to 130% TDG at three development periods between hatch and emergence (hereafter early, middle, and late stage) suffered differential mortality, growth, gas bubble disease, or seawater tolerance. Each life stage was exposed for 50 d (early stage), 29 d (middle stage), or 16 d (late stage) beginning at 13, 34, and 37 d post-hatch, respectively, through 50% emergence. The mortality for all stages from exposure to emergence was estimated to be 8% (95% confidence interval (CI) of 4% to 12%) when dissolved gas levels were between 100% and 117% TDG. Mortality significantly increased as dissolved gas levels rose above 117% TDG,; with the lethal concentration that produced 50% mortality (LC50 ) was estimated to be 128.7% TDG (95% CI of 127.2% to 130.2% TDG) in the early and middle stages. By contrast, there was no evidence that dissolved gas level significantly affected growth in any life stage except that the mean wet weight at emergence of early stage fish exposed to 130% TDG was significantly less than the modeled growth of unexposed fish. The proportion of fish afflicted with gas bubble disease increased with increasing gas concentrations and occurred most commonly in the nares and gastrointestinal tract. Early stage fish exhibited higher ratios of filament to lamellar gill chloride cells than late stage fish, and these ratios increased and decreased for early and late stage fish, respectively, as gas levels increased; however, there were no significant differences in mortality between life stages after 96 h in seawater. The study results suggest that current water quality guidelines for the management of dissolved gas appear to offer a conservative level of protection to chum salmon alevin incubating in gravel habitat downstream of Bonneville Dam.
Enhancing the efficiency of direct carbon fuel cells by bubbling Ar gas in carbon/carbonate slurry
NASA Astrophysics Data System (ADS)
Watanabe, Hirotatsu; Furuyama, Tomoaki; Okazaki, Ken
This study aims to enhance the direct carbon fuel cell (DCFC) efficiency by bubbling Ar gas in a carbon/carbonate slurry. The current discharge curve and CO and CO2 production rates were measured during discharge at 20 mA cm-2. When carbon content in carbonates (WC/carbonate) was 1.0 wt%, Ar bubbling decreased the CO/CO2 production ratio from 0.16 to 0.051, and increased the CO2 production rate, which approached the theoretical value for complete electrochemical oxidation of carbon. Moreover, bubbling increased the cell voltage by about 0.1 V at steady state. At WC/carbonate = 3.0 wt%, the CO/CO2 production ratio without bubbling increased significantly to 8.5, indicating that partial electrochemical oxidation became dominant. The C/O2- ratio is key for explaining the electrochemical oxidation of the carbon. When the C/O2- ratio was low, such as at WC/carbonate = 1.0 wt%, complete electrochemical oxidation became dominant, and bubbling enhanced the complete electrochemical oxidation. When the C/O2- ratio was high, such as at WC/carbonate = 3.0 wt%, partial electrochemical oxidation became dominant, and bubbling did not inhibit it. For WC/carbonate = 1.0 wt%, bubbling increased both coulombic and voltage efficiencies, resulting in an increase in total efficiency from 52% to 64%.
Quasi-Exact Solutions of the Equation for Description of Nonlinear Waves in a Liquid with Gas Bubbles
NASA Astrophysics Data System (ADS)
Kochanov, Mark B.; Kudryashov, Nikolay A.
Nonlinear partial differential equation derived by Kudryashov and Sinelshchikov for description of waves in a liquid with gas bubbles is considered. The quasi-exact solutions of this equation are found with the first, second and third order poles. Values of the residual function norm corresponding to all quasi-exact solutions are presented. It is shown that most quasi-exact solutions are transformed into exact solutions of nonlinear differential equation under some additional conditions. The found solutions can be used for description of nonlinear waves in a liquid with gas bubbles.
The effect on recovery of the injection of alternating slugs of gas and water at pressures above the bubble point
Givens, James Wilson
TW EFFECT ON RECOVERY OF THE INJECTION OF ALTERNATING SLUGS OF GAS AND WATER AT PRESSURES ABOVE THE BUBBLE POINT A Thesis by James Wilson Givens Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in partial... fulfillment of the requirements for the d egree of MASTERS OF SCIENCE August, l96t Major Subject; Petroleum Engineering THE EFFECT ON RECOVERY OF THE INJECTION OF ALTERNATING Sj UGS OF GAS AND WATER AT PRESSURES ABOVE THE BUBBLE POINT A Thesis...
How man-made interference might cause gas bubble emboli in deep diving whales.
Fahlman, Andreas; Tyack, Peter L; Miller, Patrick J O; Kvadsheim, Petter H
Recent cetacean mass strandings in close temporal and spatial association with sonar activity has raised the concern that anthropogenic sound may harm breath-hold diving marine mammals. Necropsy results of the stranded whales have shown evidence of bubbles in the tissues, similar to those in human divers suffering from decompression sickness (DCS). It has been proposed that changes in behavior or physiological responses during diving could increase tissue and blood N2 levels, thereby increasing DCS risk. Dive data recorded from sperm, killer, long-finned pilot, Blainville's beaked and Cuvier's beaked whales before and during exposure to low- (1-2 kHz) and mid- (2-7 kHz) frequency active sonar were used to estimate the changes in blood and tissue N2 tension (PN2 ). Our objectives were to determine if differences in (1) dive behavior or (2) physiological responses to sonar are plausible risk factors for bubble formation. The theoretical estimates indicate that all species may experience high N2 levels. However, unexpectedly, deep diving generally result in higher end-dive PN2 as compared with shallow diving. In this focused review we focus on three possible explanations: (1) We revisit an old hypothesis that CO2, because of its much higher diffusivity, forms bubble precursors that continue to grow in N2 supersaturated tissues. Such a mechanism would be less dependent on the alveolar collapse depth but affected by elevated levels of CO2 following a burst of activity during sonar exposure. (2) During deep dives, a greater duration of time might be spent at depths where gas exchange continues as compared with shallow dives. The resulting elevated levels of N2 in deep diving whales might also make them more susceptible to anthropogenic disturbances. (3) Extended duration of dives even at depths beyond where the alveoli collapse could result in slow continuous accumulation of N2 in the adipose tissues that eventually becomes a liability. PMID:24478724
How man-made interference might cause gas bubble emboli in deep diving whales
Fahlman, Andreas; Tyack, Peter L.; Miller, Patrick J. O.; Kvadsheim, Petter H.
Recent cetacean mass strandings in close temporal and spatial association with sonar activity has raised the concern that anthropogenic sound may harm breath-hold diving marine mammals. Necropsy results of the stranded whales have shown evidence of bubbles in the tissues, similar to those in human divers suffering from decompression sickness (DCS). It has been proposed that changes in behavior or physiological responses during diving could increase tissue and blood N2 levels, thereby increasing DCS risk. Dive data recorded from sperm, killer, long-finned pilot, Blainville's beaked and Cuvier's beaked whales before and during exposure to low- (12 kHz) and mid- (27 kHz) frequency active sonar were used to estimate the changes in blood and tissue N2 tension (PN2). Our objectives were to determine if differences in (1) dive behavior or (2) physiological responses to sonar are plausible risk factors for bubble formation. The theoretical estimates indicate that all species may experience high N2 levels. However, unexpectedly, deep diving generally result in higher end-dive PN2 as compared with shallow diving. In this focused review we focus on three possible explanations: (1) We revisit an old hypothesis that CO2, because of its much higher diffusivity, forms bubble precursors that continue to grow in N2 supersaturated tissues. Such a mechanism would be less dependent on the alveolar collapse depth but affected by elevated levels of CO2 following a burst of activity during sonar exposure. (2) During deep dives, a greater duration of time might be spent at depths where gas exchange continues as compared with shallow dives. The resulting elevated levels of N2 in deep diving whales might also make them more susceptible to anthropogenic disturbances. (3) Extended duration of dives even at depths beyond where the alveoli collapse could result in slow continuous accumulation of N2 in the adipose tissues that eventually becomes a liability. PMID:24478724
Effects of pulmonary gas embolism on circulation and respiration in the dog. III. Excretion of venous gas bubbles by the lung.
Verstappen, F T; Bernards, J A; Kreuzer, F
Intravenous injection of gas (10-60 ml) causes acute pulmonary embolism, which disappears completely within 10-20 min. Intravenous infusion of gas (1-5 ml min-1) can be continued for a long time. During these infusions a steady state is reached in which pulmonary arterial pressure is increased and cardiac output remains unaltered. This indicates that the degree of embolization has reached a constant level despite the continuous gas infusion. These findings can be explained by a gradual disappearance of the bubbles from the pulmonary circulation. The purpose of this study was to measure the possible excretion of gas from the intravascular gas bubbles into the alveolar air after venous administration. Neon was used as a test gas since its fractional concentration in ambient air is low (0.00018) and it can be detected by gas chromatography with sufficient accuracy. It could be demonstrated that after injection neon was present in the expiration gas. During the steady state of infusion the rate of excretion in the expiration gas appeared to be equal to the rate of infusion. Changes in the pulmonary arterial pressure curve were reflected in the neon wash-out curve. It may be concluded that during pulmonary gas embolism the administered gas is excreted into the alveolar air and that the excretion rate largely depends on the increased pulmonary arterial pressure due to the obstructing bubbles themselves. PMID:561384
Patent Holdup and Royalty Stacking* Mark A. Lemley**
Sadoulet, Elisabeth
Reply Patent Holdup and Royalty Stacking* Mark A. Lemley** & Carl Shapiro*** We argued in our article, Patent Holdup and Royalty Stacking,1 that the threat to obtain a permanent injunction can greatly enhance a patent holder's negotiating power, leading to royalty rates that exceed a benchmark level based
Sadoulet, Elisabeth
STANDARD SETTING, PATENTS, AND HOLD-UP JOSEPH FARRELL JOHN HAYES CARL SHAPIRO THERESA SULLIVAN* I. STANDARD SETTING, PATENTS, AND HOLD-UP: A TROUBLESOME MIX Standard setting raises a variety of antitrust strategy in standard setting, and Shapiro ad- dresses the boundary between cooperative standard setting
The two-phase flow at gas-evolving electrodes: Bubble-driven and Lorentz-force-driven convection
NASA Astrophysics Data System (ADS)
Weier, T.; Landgraf, S.
We observe electrolysis with gas evolution, a phenomenon occurring in a number of industrial scale electrochemical processes. Here, water electrolysis takes place in a small undivided electrolysis cell consisting of vertical electrodes embedded in a larger glass vessel which contains a dilute NaOH solution. Fluid flow velocities are measured by particle image velocimetry with fluorescent tracers, while size distribution and velocities of the bubbles are determined from bubble shadow images obtained with a high speed camera. Coalescence phenomena are observed in the flow and explain the relatively wide distribution of bubble sizes. Depending on the gap width and the current density, bubbles ascending near the electrodes form two discernible bubble curtains (low average void fraction, wide gaps) or a flow profile more akin to a channel flow (high average void fraction, small gaps). If the flow consists of separate bubble curtains, instabilities develop not unlike to those of a single phase wall jet. Finally, the influence of different wall parallel Lorentz force configurations on the velocity distribution in the cell is investigated. These Lorentz forces are generated by permanent magnets mounted behind the electrodes. Depending on gap width, current density, and magnet configuration, liquid phase velocities can be increased by several times compared to the baseline case.
3D mapping of the dense interstellar gas around the Local Bubble
NASA Astrophysics Data System (ADS)
Lallement, R.; Welsh, B. Y.; Vergely, J. L.; Crifo, F.; Sfeir, D.
We present intermediate results from a long-term program of mapping the neutral absorption characteristics of the local interstellar medium, motivated by the availability of accurate and consistent parallaxes from the Hipparcos satellite. Equivalent widths of the interstellar NaI D-line doublet at 5890 é are presented for the lines-of-sight towards some 311 new target stars lying within ~ 350 pc of the Sun. Using these data, together with NaI absorption measurements towards a further ~ 240 nearby targets published in the literature (for many of them, in the directions of molecular clouds), and the ~ 450 lines-of-sight already presented by (Sfeir et al. \\cite{sfeir99}), we show 3D absorption maps of the local distribution of neutral gas towards 1005 sight-lines with Hipparcos distances as viewed from a variety of different galactic projections. The data are synthesized by means of two complementary methods, (i) by mapping of iso-equivalent width contours, and (ii) by density distribution calculation from the inversion of column-densities, a method devised by Vergely et al. (\\cite{vergely01}). Our present data confirms the view that the local cavity is deficient in cold and neutral interstellar gas. The closest dense and cold gas ``wall'', in the first quadrant, is at ~ 55-60 pc. There are a few isolated clouds at closer distance, if the detected absorption is not produced by circumstellar material. The maps reveal narrow or wide ``interstellar tunnels'' which connect the Local Bubble to surrounding cavities, as predicted by the model of Cox & Smith (1974). In particular, one of these tunnels, defined by stars at 300 to 600 pc from the Sun showing negligible sodium absorption, connects the well known CMa void (Gry et al. \\cite{gry85}), which is part of the Local Bubble, with the supershell GSH 238+00+09 (Heiles \\cite{heiles98}). High latitude lines-of-sight with the smallest absorption are found in two ``chimneys'', whose directions are perpendicular to the Gould belt plane. The maps show that the Local Bubble is ``squeezed'' by surrounding shells in a complicated pattern and suggest that its pressure is smaller than in those expanding regions. We discuss the locations of several HI and molecular clouds. Using comparisons between NaI and HI or CO velocities, in some cases we are able to improve the constraints on their distances. According to the velocity criteria, MBM 33-37, MBM 16-18, UT 3-7, and MBM 54-55 are closer than ~ 100 pc, and MBM 40 is closer than 80 pc. Dense HI clouds are seen at less than 90 pc and 85 pc in the directions of the MBM 12 and MBM 41-43 clouds respectively, but the molecular clouds themselves may be far beyond. The above closest molecular clouds are located at the neutral boundary of the Bubble. Only one translucent cloud, G192-67, is clearly embedded within the LB and well isolated. These maps of the distribution of local neutral interstellar NaI gas are also briefly compared with the distribution of both interstellar dust and neutral HI gas within 300 pc. Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or via http:cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/411/447
Passive acoustic derived bubble flux and applications to natural gas seepage in the Mackenzie Delta, NWT, Canada and Coal Oil Point, CA
NASA Astrophysics Data System (ADS)
Culling, D.; Leifer, I.; Dallimore, S.; Alcala, K.
Methane is a prominent greenhouse gas that escapes naturally from thermogenic reservoirs as seepage from marine and lacustrine biogenic sources as bubble ebullition. Geologic methane emissions are critically important contributors to the global methane budget however, few quantitative flux measurements are available for shallow waters. This gap in knowledge is critical as in these settings gas can easily transit as bubbles through the water column and directly influence global atmospheric budgets. Video and active acoustic (sonar) measurements of bubble flux have spatial limitations requiring predictable bubble emission location. Passive acoustics are less affected by these limitations, in addition, they can provide data in water too shallow for effective sonar bubble observations. Lab tests were undertaken to quantify the acoustic signature of bubbles formed in non-cohesive sediments. specifically focusing on mechanisms that complicate interpretation of acoustic data. Lab tests then were compared to field data to provide measurement calibration/validation. The principles behind the acoustic analysis method are based on the Minnaert equation, which relates a bubble radius and acoustic frequency. Bubble size and the resultant acoustic frequency from known flows and capillary tube diameters are well documented; however changing sediment pathways adds to the complexity of bubble formation and the resultant bubble acoustic signal. These complex signals were investigated in a lab tank with a thick, cohesive fine-grained sediment bed, through which bubbles produced by a syringe pump migrated to the sediment-water interface. Then, the resultant bubbles were diverted into clear water and measured from high speed, high definition video, while the acoustic signature of bubble formation was recorded concurrently by a hydrophone. Bubble formation is influenced by currents, which shifts the acoustical signal towards a higher frequency with a more complex pattern than the Minnaert equation predicts. Furthermore, bubbles from a cohesive media escaped in pulses of multiple bubbles, which caused significant inter-bubble acoustic coupling and mud-bubble interaction. The acoustic signature of subsurface bubble migration and concurrent sediment movements, including bubble pinch off, presented additional complexities. Use of passive acoustic derived flux was applied to natural gas seepage in the Mackenzie Delta in the North West Territories, Canada as well as offshore Coal Oil Point (COP), CA. Video data were used to calibrate the COP acoustic observations and showed a strong current impact for non-cohesive sediments. Seepage flux in the delta (cohesive sediments) was calibrated using a custom turbine tent that directly measured flux. Further applications of passive acoustic-derived seep fluxes include monitoring of marine pipelines for leaks, and studying biogenic wetlands ebullition as well as thermogenic and hydrate seepage.
The objective of this study is to develop a predictive experimentally verified computational fluid dynamic (CFD) three phase model. It predicts the gas, liquid and solid hold-ups (volume fractions) and flow patterns in the industrially important bubble-coalesced (churn-turbulent) regime. The input into the model can be either particulate viscosities as measured with a Brookfield viscometer or effective restitution coefficient for particles. A combination of x-ray and {gamma}-ray densitometers was used to measure solid and liquid volume fractions. There is a fair agreement between the theory and the experiment. A CCD camera was used to measure instantaneous particle velocities. There is a good agreement between the computed time average velocities and the measurements. There is an excellent agreement between the viscosity of 800 {micro}m glass beads obtained from measurement of granular temperature (random kinetic energy of particles) and the measurement using a Brookfield viscometer. A relation between particle Reynolds stresses and granular temperature was found for developed flow. Such measurement and computations gave a restitution coefficient for a methanol catalyst to be about 0.9. A transient, two-dimensional hydrodynamic model for production of methanol from syn-gas in an Air Products/DOE LaPorte slurry bubble column reactor was developed. The model predicts downflow of catalyst at the walls and oscillatory particle and gas flow at the center, with a frequency of about 0.7 Hertz. The computed temperature variation in the rector with heat exchangers was only about 5 K, indicating good thermal management. The computed slurry height, the gas holdup and the rate of methanol production agree with LaPorte's reported data. Unlike the previous models in the literature, this model computes the gas and the particle holdups and the particle rheology. The only adjustable parameter in the model is the effective particle restitution coefficient.
Gas Bubble Trauma Monitoring in the Clearwater River Drainage, Idaho 1998.
Cochnauer, Tim
Select portions of the Clearwater and North Fork of the Clearwater rivers were electroshocked to estimate the incidence of gas bubble trauma (GBT) occurring in resident fish populations for the spring and summer months of 1998. The study area was divided into four sections and sampled weekly during periods of spill and non-spill from Dworshak Dam. Five thousand five hundred and forty one fish, representing 22 different species, were captured and examined for GBT. Two fish were detected with signs of GBT; exhibiting the lowest incidence of GBT in the last four years (0.04%). Reduced discharge and lower levels of total dissolved gases may have resulted in lower incidence of GBT in the 1998 monitoring period.
Fuel Performance Experiments and Modeling: Fission Gas Bubble Nucleation and Growth in Alloy Nuclear Fuels
McDeavitt, Sean; Shao, Lin; Tsvetkov, Pavel; Wirth, Brian; Kennedy, Rory
Advanced fast reactor systems being developed under the DOE's Advanced Fuel Cycle Initiative are designed to destroy TRU isotopes generated in existing and future nuclear energy systems. Over the past 40 years, multiple experiments and demonstrations have been completed using U-Zr, U-Pu-Zr, U-Mo and other metal alloys. As a result, multiple empirical and semi-empirical relationships have been established to develop empirical performance modeling codes. many mechamistic questions about fission as mobility, bubble coalescience, and gas release have been answered through industrial experience, reearch, and empirical understanding. The advent of modern computational materials science, however, opens new doors of development such that physics-based multi-scale models may be developed to enable a new generation of predictive fuel performance codes that are not limited by empiricism.
Relationship of the time course of venous gas bubbles to altitude decompression illness
NASA Technical Reports Server (NTRS)
Conkin, J.; Foster, P. P.; Powell, M. R.; Waligora, J. M.
The correlation is low between the occurrence of gas bubbles in the pulmonary artery, called venous gas emboli (VGE), and subsequent decompression illness (DCI). The correlation improves when a "grade" of VGE is considered; a zero to four categorical classification based on the intensity and duration of the VGE signal from a Doppler bubble detector. Additional insight about DCI might come from an analysis of the time course of the occurrence of VGE. Using the NASA Hypobaric Decompression Sickness Databank, we compared the time course of the VGE outcome between 322 subjects who exercised and 133 Doppler technicians who did not exercise to evaluate the role of physical activity on the VGE outcome and incidence of DCI. We also compared 61 subjects with VGE and DCI with 110 subjects with VGE but without DCI to identify unique characteristics about the time course of the VGE outcome to try to discriminate between DCI and no-DCI cases. The VGE outcome as a function of time showed a characteristic short lag, rapid response, and gradual recovery phase that was related to physical activity at altitude and the presence or absence of DCI. The average time for DCI symptoms in a limb occurred just before the time of the highest fraction of VGE in the pulmonary artery. It is likely, but not certain, that an individual will report a DCI symptom if VGE are detected early in the altitude exposure, the intensity or grade of VGE rapidly increases from a limb region, and the intensity or grade of VGE remains high.
Sparger Effects on Gas Volume Fraction Distributions in Vertical Bubble-Column Flows as Measured by Gamma-Densitometry Tomography
Gamma-densitometry tomography is applied to study the effect of sparger hole geometry, gas flow rate, column pressure, and phase properties on gas volume fraction profiles in bubble columns. Tests are conducted in a column 0.48 m in diameter, using air and mineral oil, superficial gas velocities ranging from 5 to 30 cm s{sup -1}, and absolute column pressures from 103 to 517 kPa. Reconstructed gas volume fraction profiles from two sparger geometries are presented. The development length of the gas volume fraction profile is found to increase with gas flow rate and column pressure. Increases in gas flow rate increase the local gas volume fraction preferentially on the column axis, whereas increases in column pressure produce a uniform rise in gas volume fraction across the column. A comparison of results from the two spargers indicates a significant change in development length with the number and size of sparger holes.
Deterministic chaos in the gas inlet pressure of gasliquid bubbling systems
Louis John Mittoni; Mark Philip Schwarz; Robert David La Nauze
In an attempt to assess the suggestion that submerged gas injection can under certain conditions be described as exhibiting chaotic dynamics, a short analysis has been undertaken on the results of a set of experiments over a limited set of conditions including the variation of chamber volume, injection nozzle diameter, liquid viscosity, and gas flow rate at a temperature of
Low liquid loading gas-liquid two-phase flow in near- horizontal pipes
NASA Astrophysics Data System (ADS)
Meng, Weihong
Low liquid loading gas-liquid two-phase flow in near- horizontal pipes has been studied both experimentally and theoretically. A new state-of-the-art, air-oil test facility was designed, constructed and operated. A transparent test section (50.1-cm ID x 19-m long) could be inclined within +/-2¯ from the horizontal. Mineral oil was used as the liquid phase (?L = 5.66 mPa.s, ?L = 877 kg/m3, and ? = 30 dynes/cm at 23.9¯C) and air was used as the gas phase. The measured parameters included gas flow rate, liquid flow rate, pressure, differential pressure, temperature, liquid holdup, liquid film flow rate, droplet entrainment fraction, droplet deposition rate and liquid film thickness at the bottom of the pipe. A surprising phenomenon was observed; at high gas velocities (annular flow), liquid film flow rate, liquid holdup and pressure gradient decreased as liquid velocity increased. The reason is believed to be the effect of droplet entrainment on the gas stream. Countercurrent flow and vortices in the liquid film were observed in upward inclined flows. Gas bubbles were observed in the liquid film at all five inclination angles. A two-fluid model was developed for low liquid loading flows. New correlations were proposed for the interfacial friction factor. The effect of droplet entrainment on the interfacial friction factor is also evaluated. The predictions of liquid holdup and pressure gradient from the new models matched well with the experimental data.
Inertial-Fusion-Related Hydrodynamic Instabilities in a Spherical Gas Bubble Accelerated by a Planar Shock Wave
Niederhaus, John [University of Wisconsin-Madison (United States); Ranjan, Devesh [University of Wisconsin-Madison (United States); Anderson, Mark [University of Wisconsin-Madison (United States); Oakley, Jason [University of Wisconsin-Madison (United States); Bonazza, Riccardo [University of Wisconsin-Madison (United States); Greenough, Jeff [Lawrence Livermore National Laboratory (United States)
Experiments studying the compression and unstable growth of a dense spherical bubble in a gaseous medium subjected to a strong planar shock wave (2.8 < M < 3.4) are performed in a vertical shock tube. The test gas is initially contained in a free-falling spherical soap-film bubble, and the shocked bubble is imaged using planar laser diagnostics. Concurrently, simulations are carried out using a compressible hydrodynamics code in r-z axisymmetric geometry.Experiments and computations indicate the formation of characteristic vortical structures in the post-shock flow, due to Richtmyer-Meshkov and Kelvin-Helmholtz instabilities, and smaller-scale vortices due to secondary effects. Inconsistencies between experimental and computational results are examined, and the usefulness of the current axisymmetric approach is evaluated.
Degradation mechanisms of 4-chlorophenol in a novel gasliquid hybrid discharge reactor by pulsed high voltage system with oxygen or nitrogen bubbling
Yi Zhang; Minghua Zhou; Xiaolong Hao; Lecheng Lei
The effect of gas bubbling on the removal efficiency of 4-chlorophenol (4-CP) in aqueous solution has been investigated using a novel pulsed high voltage gasliquid hybrid discharge reactor, which generates gas-phase discharge above the water surface simultaneously with the spark discharge directly in the liquid. The time for 100% of 4-CP degradation in the case of oxygen bubbling (7min) was
SNM holdup assessment of Los Alamos exhaust ducts. Final report
Marshall, R.S.
Fissile material holdup in glovebox and fume hood exhaust ducting has been quantified for all Los Alamos duct systems. Gamma-based, nondestructive measurements were used to quantify holdup. The measurements were performed during three measurement campaigns. The first campaign, Phase I, provided foot-by-foot, semiquantitative measurement data on all ducting. These data were used to identify ducting that required more accurate (quantitative) measurement. Of the 280 duct systems receiving Phase I measurements, 262 indicated less than 50 g of fissile holdup and 19 indicated fissile holdup of 50 or more grams. Seven duct systems were measured in a second campaign, called Series 1, Phase II. Holdup estimates on these ducts ranged from 421 g of {sup 235}U in a duct servicing a shut-down uranium-machining facility to 39 g of {sup 239}Pu in a duct servicing an active plutonium-processing facility. Measurements performed in the second campaign proved excessively laborious, so a third campaign was initiated that used more efficient instrumentation at some sacrifice in measurement quality. Holdup estimates for the 12 duct systems measured during this third campaign ranged from 70 g of {sup 235}U in a duct servicing analytical laboratories to 1 g of {sup 235}U and 1 g of {sup 239}Pu in a duct carrying exhaust air to a remote filter building. These quantitative holdup estimates support the conclusion made at the completion of the Phase I measurements that only ducts servicing shut-down uranium operations contain about 400 g of fissile holdup. No ventilation ducts at Los Alamos contain sufficient fissile material holdup to present a criticality safety concern.
Evidence of injury caused by gas bubbles in a live marine mammal: barotrauma in a California sea lion Zalophus californianus.
Van Bonn, W; Montie, E; Dennison, S; Pussini, N; Cook, P; Greig, D; Barakos, J; Colegrove, K; Gulland, F
A yearling male California sea lion Zalophus californianus with hypermetric ataxia and bilateral negative menace reflexes was brought to The Marine Mammal Center, Sausalito, California, U.S.A., in late 2009 for medical assessment and treatment. The clinical signs were due to multiple gas bubbles within the cerebellum. These lesions were intraparenchymal, multifocal to coalescing, spherical to ovoid, and varied from 0.5 to 2.4 cm diameter. The gas composed 21.3% of the total cerebellum volume. Three rib fractures were also noted during diagnostic evaluation and were presumed to be associated with the gas bubbles in the brain. The progression of clinical signs and lesion appearance were monitored with magnetic resonance imaging, cognitive function testing and computed tomography. Gas filled voids in the cerebellum were filled with fluid on follow up images. Clinical signs resolved and the sea lion was released with a satellite tag attached. Post release the animal travelled approximately 75 km north and 80 km south of the release site and the tag recorded dives of over 150 m depth. The animal re-stranded 25 d following release and died of a subacute bronchopneumonia and pleuritis. This is the first instance of clinical injury due to gas bubble formation described in a living pinniped and the first sea lion with quantifiable cerebellar damage to take part in spatial learning and memory testing. PMID:22013748
Visuri, Steven R. (Livermore, CA); Mammini, Beth M. (Walnut Creek, CA); Da Silva, Luiz B. (Danville, CA); Celliers, Peter M. (Berkeley, CA)
The present invention is intended as a means of diagnosing the presence of a gas bubble and incorporating the information into a feedback system for opto-acoustic thrombolysis. In opto-acoustic thrombolysis, pulsed laser radiation at ultrasonic frequencies is delivered intraluminally down an optical fiber and directed toward a thrombus or otherwise occluded vessel. Dissolution of the occlusion is therefore mediated through ultrasonic action of propagating pressure or shock waves. A vapor bubble in the fluid surrounding the occlusion may form as a result of laser irradiation. This vapor bubble may be used to directly disrupt the occlusion or as a means of producing a pressure wave. It is desirable to detect the formation and follow the lifetime of the vapor bubble. Knowledge of the bubble formation and lifetime yields critical information as to the maximum size of the bubble, density of the absorbed radiation, and properties of the absorbing material. This information can then be used in a feedback system to alter the irradiation conditions.
Storm in a "Teacup": A Radio-quiet Quasar with ?10 kpc Radio-emitting Bubbles and Extreme Gas Kinematics
NASA Astrophysics Data System (ADS)
Harrison, C. M.; Thomson, A. P.; Alexander, D. M.; Bauer, F. E.; Edge, A. C.; Hogan, M. T.; Mullaney, J. R.; Swinbank, A. M.
We present multi-frequency (1-8 GHz) Very Large Array data, combined with VIsible MultiObject Spectrograph integral field unit data and Hubble Space Telescope imaging, of a z = 0.085 radio-quiet type 2 quasar (with L 1.4 GHz ? 5 æ 1023 W Hz1 and L AGN ? 2 æ 1045 erg s1). Due to the morphology of its emission-line region, the target (J1430+1339) has been referred to as the "Teacup" active galactic nucleus (AGN) in the literature. We identify "bubbles" of radio emission that are extended ?10-12 kpc to both the east and west of the nucleus. The edge of the brighter eastern bubble is co-spatial with an arc of luminous ionized gas. We also show that the "Teacup" AGN hosts a compact radio structure, located ?0.8 kpc from the core position, at the base of the eastern bubble. This radio structure is co-spatial with an ionized outflow with an observed velocity of v = 740 km s1. This is likely to correspond to a jet, or possibly a quasar wind, interacting with the interstellar medium at this position. The large-scale radio bubbles appear to be inflated by the central AGN, which indicates that the AGN can also interact with the gas on >~ 10 kpc scales. Our study highlights that even when a quasar is formally "radio-quiet" the radio emission can be extremely effective for observing the effects of AGN feedback.
Segregating gas from melt: an experimental study of the Ostwald ripening of vapor bubbles in magmas
Lautze, Nicole C.; Sisson, Thomas W.; Mangan, Margaret T.; Grove, Timothy L.
Diffusive coarsening (Ostwald ripening) of H2O and H2O-CO2 bubbles in rhyolite and basaltic andesite melts was studied with elevated temperaturepressure experiments to investigate the rates and time spans over which vapor bubbles may enlarge and attain sufficient buoyancy to segregate in magmatic systems. Bubble growth and segregation are also considered in terms of classical steady-state and transient (non-steady-state) ripening theory. Experimental results are consistent with diffusive coarsening as the dominant mechanism of bubble growth. Ripening is faster in experiments saturated with pure H2O than in those with a CO2-rich mixed vapor probably due to faster diffusion of H2O than CO2 through the melt. None of the experimental series followed the time1/3 increase in mean bubble radius and time-1 decrease in bubble number density predicted by classical steady-state ripening theory. Instead, products are interpreted as resulting from transient regime ripening. Application of transient regime theory suggests that bubbly magmas may require from days to 100 years to reach steady-state ripening conditions. Experimental results, as well as theory for steady-state ripening of bubbles that are immobile or undergoing buoyant ascent, indicate that diffusive coarsening efficiently eliminates micron-sized bubbles and would produce mm-sized bubbles in 102104 years in crustal magma bodies. Once bubbles attain mm-sizes, their calculated ascent rates are sufficient that they could transit multiple kilometers over hundreds to thousands of years through mafic and silicic melt, respectively. These results show that diffusive coarsening can facilitate transfer of volatiles through, and from, magmatic systems by creating bubbles sufficiently large for rapid ascent.
Dynamics of a Spherical Vapor\\/Gas Bubble in Varying Pressure Fields
Hisanobu Kawashima; Masaharu Kameda
A mathematical model is developed to simulate the radial motion of cavitation bubbles. The heat and mass transports including phase change are formulated precisely. In order to reduce the computational cost without loss of the important thermo-fluid phenomena, two simplifications are employed: time-dependent bubble radius is described using the Rayleigh-Plesset equation; the pressure in the bubble is assumed to be
Comparative study of gas-liquid mass transfer coefficients in stirred autoclaves, tubing bomb microreactors, and bubble columns
Gollakota, S.V.; Guln, J.A.
The relative gas-liquid contacting coefficients were examined for three reactor types commonly used for direct coal liquefaction. These reactors were the tubing bomb microreactor (TBMR), the magnetically driven batch autoclave with gas-inducing impeller, and the bubble column. The same chemical system, sulfite oxidation in the presence of cobaltous ion catalyst, was used in comparing the performance of the various reactors. Experimental results were obtained in this work for the TBMR and the stirred autoclave, while literature values using sulfite oxidation were utilized for bubble column characterization. The effect of two particle sizes of inert solids on the gas-liquid mass transfer parameters also was determined. The TBMR was the most effective gas-liquid contacting device, with interfacial areas up to 28 cm/sup -1/ being realized. Using literature results obtained with the sulfite oxidation system, the bubble column was found to have comparatively low mass transfer coefficients. Generally, small particles had little effect up to 40 wt % loading, although significant increases were obtained in certain instances in the stirred autoclave reactor.
ERIC Educational Resources Information Center
Kim, Hy
A simple oxygen-collecting device (easily constructed from glass jars and a lid) can show bubbles released by water plants during photosynthesis. Suggestions are given for: (1) testing the collected gas; (2) using various carbon dioxide sources; and (3) measuring respiration. (DH)
Deterministic chaos in the gas inlet pressure of gas-liquid bubbling systems
NASA Astrophysics Data System (ADS)
Mittoni, Louis John; Schwarz, Mark Philip; La Nauze, Robert David
In an attempt to assess the suggestion that submerged gas injection can under certain conditions be described as exhibiting chaotic dynamics, a short analysis has been undertaken on the results of a set of experiments over a limited set of conditions including the variation of chamber volume, injection nozzle diameter, liquid viscosity, and gas flow rate at a temperature of 20 ¯C. A convenient noninvasive approach is demonstrated using the upstream pressure signal to reconstruct the return map attractors. The classic period doubling sequence leading to irregular behavior is observed only over certain system parameter ranges. The important parameters believed to be responsible for the deterministic chaotic behavior and their relationship are briefly discussed.
Gas-solid fluidized bed reactors: Scale-up, flow regimes identification and hydrodynamics
NASA Astrophysics Data System (ADS)
Zaid, Faraj Muftah
This research studied the scale-up, flow regimes identification and hydrodynamics of fluidized beds using 6-inch and 18- inch diameter columns and different particles. One of the objectives was to advance the scale-up of gas-solid fluidized bed reactors by developing a new mechanistic methodology for hydrodynamic similarity based on matching the radial or diameter profile of gas phase holdup, since gas dynamics dictate the hydrodynamics of these reactors. This has been successfully achieved. However, the literature reported scale-up methodology based on matching selected dimensionless groups was examined and it was found that it was not easy to match the dimensionless groups and hence, there was some deviation in the hydrodynamics of the studied two different fluidized beds. A new technique based on gamma ray densitometry (GRD) was successfully developed and utilized to on-line monitor the implementation of scale-up, to identify the flow regime, and to measure the radial or diameter profiles of gas and solids holdups. CFD has been demonstrated as a valuable tool to enable the implementation of the newly developed scale-up methodology based on finding the conditions that provide similar or closer radial profile or cross sectional distribution of the gas holdup. As gas velocity increases, solids holdup in the center region of the column decreases in the fully developed region of both 6 inch and 18 inch diameter columns. Solids holdup increased with the increase in the particles size and density. Upflowing particles velocity increased with the gas velocity and became steeper at high superficial gas velocity at all axial heights where the center line velocity became higher than that in the wall region. Smaller particles size and lower density gave larger upflowing particles velocity. Minimum fluidization velocity and transition velocity from bubbly to churn turbulent flow regimes were found to be lower in 18 inch diameter column compared to those obtained in 6 inch diameter column. Also the absolute fluctuation of upflowing particles velocity multiplied by solids holdups v? 3? as one of the terms for solids mass flux estimation was found to be larger in 18-inch diameter column than that in 6-inch diameter column using same particles size and density.
Influence of argon gas bubbles and non-metallic inclusions on the flow behavior in steel continuous casting
C. Pfeiler; M. Wu; A. Ludwig
The present study uses an EulerianLagrangian approach to model the 3D turbulence (k?) flow of the steel melt (continuous phase) and the trajectories of individual non-metallic inclusions and gas bubbles (dispersed phase) in a continuous casting. The dispersed phase is considered as numerous mass-loaded particles with different classes of diameters and densities. To consider the interaction between the continuous and
Small Gas Bubble Experiment for Mitigation of Cavitation Damage and Pressure Waves in Short-pulse Mercury Spallation Targets
Wendel, Mark W [ORNL] [ORNL; Felde, David K [ORNL] [ORNL; Sangrey, Robert L [ORNL] [ORNL; Abdou, Ashraf A [ORNL] [ORNL; West, David L [ORNL] [ORNL; Shea, Thomas J [ORNL] [ORNL; Hasegawa, Shoichi [Japan Atomic Energy Agency (JAEA)] [Japan Atomic Energy Agency (JAEA); Kogawa, Hiroyuki [Japan Atomic Energy Agency (JAEA)] [Japan Atomic Energy Agency (JAEA); Naoe, Dr. Takashi [Japan Atomic Energy Agency (JAEA)] [Japan Atomic Energy Agency (JAEA); Farny, Dr. Caleb H. [Boston University] [Boston University; Kaminsky, Andrew L [ORNL] [ORNL
Populations of small helium gas bubbles were introduced into a flowing mercury experiment test loop to evaluate mitigation of beam-pulse induced cavitation damage and pressure waves. The test loop was developed and thoroughly tested at the Spallation Neutron Source (SNS) prior to irradiations at the Los Alamos Neutron Science Center - Weapons Neutron Research Center (LANSCE-WNR) facility. Twelve candidate bubblers were evaluated over a range of mercury flow and gas injection rates by use of a novel optical measurement technique that accurately assessed the generated bubble size distributions. Final selection for irradiation testing included two variations of a swirl bubbler provided by Japan Proton Accelerator Research Complex (J-PARC) collaborators and one orifice bubbler developed at SNS. Bubble populations of interest consisted of sizes up to 150 m in radius with achieved gas void fractions in the 10^-5 to 10^-4 range. The nominal WNR beam pulse used for the experiment created energy deposition in the mercury comparable to SNS pulses operating at 2.5 MW. Nineteen test conditions were completed each with 100 pulses, including variations on mercury flow, gas injection and protons per pulse. The principal measure of cavitation damage mitigation was surface damage assessment on test specimens that were manually replaced for each test condition. Damage assessment was done after radiation decay and decontamination by optical and laser profiling microscopy with damaged area fraction and maximum pit depth being the more valued results. Damage was reduced by flow alone; the best mitigation from bubble injection was between half and a quarter that of flow alone. Other data collected included surface motion tracking by three laser Doppler vibrometers (LDV), loop wall dynamic strain, beam diagnostics for charge and beam profile assessment, embedded hydrophones and pressure sensors, and sound measurement by a suite of conventional and contact microphones.
Hydrodynamics of slurry bubble column during dimethyl ether (DME) synthesis: Gasliquid recirculation model and radioactive tracer studies
P. Chen; P. Gupta; M. P. Dudukovic; B. A. Toseland
Radioactive tracer measurements, using impulse injections of Ar41, powdered oxide of Mn56 and real catalyst particles doped with an oxide of Mn56, conducted at the Advance Fuels Development Unit (AFDU) slurry bubble column (BC) reactor during dimethyl ether (DME) synthesis (reactor pressure of 5.27MPa, reactor temperature of T=250?C, inlet superficial gas velocity of 17.1cm\\/s, and a catalyst loading of 36wt%)
NSDL National Science Digital Library
Glenn Dolphin
In this activity, which can be performed as a demonstration by the teacher or by the students themselves, carbon dioxide is generated in a fish tank using sodium bicarbonate and vinegar. The students can observe as the accumulating carbon dioxide extinguishes candles of different heights, marking rising levels of CO2 in the tank. They can also blow soap bubbles (which contain air) into the tank and observe them floating on the denser CO2 at first, then sinking as the gas diffuses through the soap film that forms the bubbles.
Experiments on the motion of gas bubbles in turbulence generated by an active grid
NASA Astrophysics Data System (ADS)
Poorte, R. E. G.; Biesheuvel, A.
The random motion of nearly spherical bubbles in the turbulent flow behind a grid is studied experimentally. In quiescent water these bubbles rise at high Reynolds number. The turbulence is generated by an active grid of the design of Makita (1991), and can have turbulence Reynolds number R[lambda] of up to 200. Minor changes in the geometry of the grid and in its mode of operation improves the isotropy of the turbulence, compared with that reported by Makita (1991) and Mydlarski & Warhaft (1996). The trajectory of each bubble is measured with high spatial and temporal resolution with a specially developed technique that makes use of a position-sensitive detector. Bubble statistics such as the mean rise velocity and the root-mean-square velocity fluctuations are obtained by ensemble averaging over many identical bubbles. The resulting bubble mean rise velocity is significantly reduced (up to 35%) compared with the quiescent conditions. The vertical bubble velocity fluctuations are found to be non-Gaussian, whereas the horizontal displacements are Gaussian for all times. The diffusivity of bubbles is considerably less than that of fluid particles. These findings are qualitatively consistent with results obtained through theoretical analysis and numerical simulations by Spelt & Biesheuvel (1997).
Effect of Particles on Electrical Charge of Gas Bubbles by Yiying Li
Barthelat, Francois
coalescence Practical importance in flotation processes used for Mineral separation Potable water treatment bubbles influence Metal ion, solid particle and oil droplet attachment Bubble size distribution through but is now used in a variety of industries. Hydrophobicity is the physical property of water repulsion
Testing a simple model of gas bubble dynamics in porous media
NASA Astrophysics Data System (ADS)
Ramirez, Jorge A.; Baird, Andy J.; Coulthard, Tom J.; Waddington, J. Michael
Bubble dynamics in porous media are of great importance in industrial and natural systems. Of particular significance is the impact that bubble-related emissions (ebullition) of greenhouse gases from porous media could have on global climate (e.g., wetland methane emissions). Thus, predictions of future changes in bubble storage, movement, and ebullition from porous media are needed. Methods exist to predict ebullition using numerical models, but all existing models are limited in scale (spatial and temporal) by high computational demands or represent porous media simplistically. A suitable model is needed to simulate ebullition at scales beyond individual pores or relatively small collections (<10-4 m3) of connected pores. Here we present a cellular automaton model of bubbles in porous media that addresses this need. The model is computationally efficient, and could be applied over large spatial and temporal extent without sacrificing fine-scale detail. We test this cellular automaton model against a physical model and find a good correspondence in bubble storage, bubble size, and ebullition between both models. It was found that porous media heterogeneity alone can have a strong effect on ebullition. Furthermore, results from both models suggest that the frequency distributions of number of ebullition events per time and the magnitude of bubble loss are strongly right skewed, which partly explains the difficulty in interpreting ebullition events from natural systems.
Mass transfer processes across the Capillary Fringe: Quantification of gas-water interface and bubble mediated mass transfer
NASA Astrophysics Data System (ADS)
Geistlinger, Helmut; Mohammadian, Sadjad; Schl■ter, Steffen; Karimzadeh, Lotfollah; Vogel, Hans-J—rg
The Capillary Fringe (CF) is a highly dynamic zone at the interface between the water-saturated aquifer and the vadose zone, where steep biogeochemical gradients and thus high bioactivities are expected. Mass transfer processes between the unsaturated zone and the atmosphere, like Greenhouse gas emissions and evaporation, are controlled by the highly temporal and spatial variable gas-water interface across the capillary fringe. Due to water table fluctuations, gas phase may be entrapped or released at/from the CF, which extremely affects the hydraulic properties of the porous medium as well as the mass transfer processes in the partially saturated zone. Most of these processes (gas entrapment and bubble mediated mass transfer (BMT)) are governed by the interactions between the interfaces of gas, water and soil phases. Quantification of these parameters requires a pore-scale approach, which can determine the phase volumes and interfaces with high accuracy. For the understanding and prediction of the involved processes, experiments and modeling at the pore scale are the necessary prerequisites for upscaled, effective modeling approaches. To achieve this aim, we conducted a set of column experiments using X-Ray Computed Tomography (CT). Using this technique, we are able to quantitatively analyze the desired variables in 3D inside the actual bulk volume of the porous media. Water table (WT) elevation was raised at different velocities in the column filled with 1mm-glass beads. After each rise, the column was scanned with CT. We used an intelligent multi-phase segmentation method, considering grey value frequency and voxel neighboring, to separate gas, water, and solid phases in the CT images. The saturation of the gas phase, distribution of the trapped gas bubbles and clusters, and their size, shape, and area are quantified and analyzed at pore-scale. We developed a new segmentation algorithm to distinguish the gas/water interface from the gas/solid interface. Only the first plays the key role in BMT. Parallel to the CT-column experiments we measured in the same experimental setup (column, sediment, WT-rise velocity) the dissolution of trapped Oxygen gas bubbles using optode spots along the capillary fringe inside the column. For the first time we quantify BMT based on pore-scale process characteristics of gas phase distribution using two different models: (i) an effective 1D-diffusion model and (ii) a Multisphere diffusion model.
Engineering Development of Slurry Bubble Column Reactor (SBCR) Technology
Puneet Gupta
This report summarizes the procedures used and results obtained in determining radial gas holdup profiles, via gamma ray scanning, and in assessing liquid and gas mixing parameters, via radioactive liquid and gas tracers, during Fischer Tropsch synthesis. The objectives of the study were (i) to develop a procedure for detection of gas holdup radial profiles in operating reactors and (ii) to test the ability of the developed, previously described, engineering models to predict the observed liquid and gas mixing patterns. It was shown that the current scanning procedures were not precise enough to obtain an accurate estimate of the gas radial holdup profile and an improved protocol for future use was developed. The previously developed physically based model for liquid mixing was adapted to account for liquid withdrawal from the mid section of the column. The ability of our engineering mixing models for liquid and gas phase to predict both liquid and gas phase tracer response was established and illustrated.
Evaluation of the Integrated Holdup Measurement System with the M3(superscript 3)CA for Assay of Uranium and Plutonium Holdup
P. A. Russo; J. K. Sprinkle, Jr.; C. W. Bjork; T. O. McKown; G. A. Sheppard; S. E. Smith; J. F. Harris
Uranium and plutonium holdup that has been simulated by insertion of a variety of sealed, reference samples into pipes, ducts, and other hardware has been measured over a period of six years with an integrated holdup measurement system. The result is a systematic evaluation of the generalized-geometry holdup (GGH) formalism applied to portable gamma-ray holdup measurements with low-resolution detectors. The extended exercise was carried out both with and without automation of the measurements, data reduction/analysis, and holdup evaluation. Automation was accomplished by the software Version 2 for the Holdup Measurement System (HMS2). The purpose of the exercise was to establish reliable benchmarks for GGH measurements and to document the advantages of the automation with actual measurement results. The results presented below demonstrate a factor of 2 improvement in the quantitative reliability of the holdup assay automated by HMS2. The automated results are otherwise identical to the manual measurements. These and similar exercises also show that automation can decrease by a factor of 20 or more the time required to execute a holdup measurement campaign and obtain the holdup quantities for the facility using an integrated holdup measurement system, and that only one person, rather than two, is required to perform the measurements. Enhanced implementation of the integrated holdup measurement system with new software, corrections for systematic effects, and improved room-temperature gamma-ray detectors is planned.
Single-bubble sonoluminescence
Michael P. Brenner; Sascha Hilgenfeldt; Detlef Lohse
Single-bubble sonoluminescence occurs when an acoustically trapped and periodically driven gas bubble collapses so strongly that the energy focusing at collapse leads to light emission. Detailed experiments have demonstrated the unique properties of this system: the spectrum of the emitted light tends to peak in the ultraviolet and depends strongly on the type of gas dissolved in the liquid; small
The effect of extended O2 prebreathing on altitude decompression sickness and venous gas bubbles
NASA Technical Reports Server (NTRS)
Waligora, James M.; Horrigan, David J.; Conkin, Johnny
The purpose of this study was to determine the effect of extended O2 prebreathing on symptom and bubble incidence during decompressions simulating extravehicular activity. The 38 subjects breathed O2 for a 6-hr period prior to decompression to 4.3 psi. The subjects performed upper body exercises for 6 hr. Eight subjects were exposed to the same protocol after an 8-hr prebreathe. Venous bubbles were detected in 18 of 38 subjects decompressed after the 6-hr prebreathe. Four of these subjects reported symptoms of altitude decompression sickness. No symptoms or bubbles were detected in the eight subjects who had prebreathed 8 hr. The incidence of symptoms and bubbles, when combined with prior data on 3.5- and 4.0-hr prebreathes, showed an inverse correlation to prebreathing time. The incidence of symptoms was higher than has been reported for subjects exposed to decompression of shorter duration with less activity.
Nigmatulin, R.I. [Tyumen Institute of Mechanics of Multiphase Systems (TIMMS), Marx (Russian Federation); Lahey, R.T. Jr. [Rensselaer Polytechnic Institute, Troy, NY (United States)
In this paper a new method for the realization of fusion energy is presented. This method is based on the superhigh compression of a gas bubble (deuterium or deuterium/thritium) in heavy water or another liquid. The superhigh compression of a gas bubble in a liquid is achieved through forced non-linear, non-periodic resonance oscillations using moderate amplitudes of forcing pressure. The key feature of this new method is a coordination of the forced liquid pressure change with the change of bubble volume. The corresponding regime of the bubble oscillation has been called {open_quotes}basketball dribbling (BD) regime{close_quotes}. The analytical solution describing this process for spherically symmetric bubble oscillations, neglecting dissipation and compressibility of the liquid, has been obtained. This solution shown no limitation on the supercompression of the bubble and the corresponding maximum temperature. The various dissipation mechanisms, including viscous, conductive and radiation heat losses have been considered. It is shown that in spite of these losses it is possible to achieve very high gas bubble temperatures. This because the time duration of the gas bubble supercompression becomes very short when increasing the intensity of compression, thus limiting the energy losses. Significantly, the calculated maximum gas temperatures have shown that nuclear fusion may be possible. First estimations of the affect of liquid compressibility have been made to determine possible limitations on gas bubble compression. The next step will be to investigate the role of interfacial instability and breaking down of the bubble, shock wave phenomena around and in the bubble and mutual diffusion of the gas and the liquid.
Novel techniques for slurry bubble column hydrodynamics
Dudukovic, M.P.
The objective of this cooperative research effort between Washington University, Ohio State University and Exxon Research Engineering Company was to improve the knowledge base for scale-up and operation of slurry bubble column reactors for syngas conversion and other coal conversion processes by increased reliance on experimentally verified hydrodynamic models. During the first year (July 1, 1995--June 30, 1996) of this three year program novel experimental tools (computer aided radioactive particle tracking (CARPT), particle image velocimetry (PIV), heat probe, optical fiber probe and gamma ray tomography) were developed and tuned for measurement of pertinent hydrodynamic quantities, such as velocity field, holdup distribution, heat transfer and bubble size. The accomplishments were delineated in the First Technical Annual Report. The second year (July, 1996--June 30, 1997) was spent on further development and tuning of the novel experimental tools (e.g., development of Monte Carlo calibration for CARPT, optical probe development), building up the hydrodynamic data base using these tools and comparison of the two techniques (PIV and CARPT) for determination of liquid velocities. A phenomenological model for gas and liquid backmixing was also developed. All accomplishments were summarized in the Second Annual Technical Report. During the third and final year of the program (July 1, 1997--June 30, 1998) and during the nine months no cost extension, the high pressure facility was completed and a set of data was taken at high pressure conditions. Both PIV, CT and CARPT were used. More fundamental hydrodynamic modeling was also undertaken and model predictions were compared to data. The accomplishments for this period are summarized in this report.
The North Sea Blowout: A gas bubble megaplume with spiral vortex motion and why it might, or might not, contribute much to the atmospheric methane
NASA Astrophysics Data System (ADS)
Schneider von Deimling, Jens; Leifer, Ira; Schmidt, Mark; Rehder, Gregor; Linke, Peter
In the Central North Sea, during drilling operations, a gas blowout accident happened in 1990. Thereafter, natural gas has leaked prodigiously from a 60 m diameter and 20 m deep crater located at 95 m depth into the water column and to the sea surface. A series of field studies was carried out at this site since 2005 evidencing ongoing intense seepage activity. Three gas bubble megaplumes and dozens of minor to major bubble seeps were observed in the crater during a manned submersible dive, ROV mapped hundreds. Analysis of gas bubbles captured at 118 m water depth revealed concentrations between 88-90%Vol CH4 with ? 13C-CH4 values around -74 VPDB, consistent with a biogenic origin. Blowout site flux estimates derived from ROV video show the site's emissions are the strongest and most intense marine methane seepage quantified to date with seabed emissions of ~32.6 kt/y. Based on previous research suggesting greater flux correlates with greater transport efficiency, the direct bubble-mediated atmospheric flux to the atmosphere was estimated at a surprisingly low 0.7kt/y. This is orders of magnitude smaller compared to the seabed flux, thus the bulk methane dissolves before reaching the atmosphere, suggesting enhanced bubble dissolution rates for megaplumes. Analysis of more than 120 water samples from near the blowout plume showed dissolved methane concentration distributions consistent with enhanced bubble dissolution at depth. CH4 concentrations ranged from 0.2 çmol/L at 20 m depth to a peak in the crater of an extraordinary 400 çmol/L. To evaluate further the controlling factors on the rising bubble plume, multibeam water column data were analyzed. The bubble plume spatial distribution revealed a horizontal intrusion of gas bubbles just below the thermocline. This pronounced pattern was traced 200 m horizontally with a downflow plume orientation suggesting trapping of methane-enriched fluids at depth. A numerical bubble propagation model was used to simulate the extraordinarily intense Blowout site plume. Simulations that used normal bubble dissolution rates were unable to explain the observed trapping of almost all methane at depth, even when neglecting the observed very strong upwelling flows at the site. Incorporating a hypothesized enhanced bubble gas exchange rate allowed reproduction of observations. Video and multibeam water column analyses revealed significant turbulence in and around the bubble plume on decimeter and meter scale. Moreover 3D water column assessments by multibeam reveal that the gas ebullitions merge into a 20 m wide spiral vortex extending throughout the water column. Spiral vortex formation never has been reported for gas seepage and may be an important process enhancing plume methane dissolution. Numerical simulations incorporating vortical bubble trapping (slow rise) and enhanced bubble gas exchange were able to reproduce observations. Thus, megaplume processes could explain the surprising low surface methane observations, with important implications for understanding the fate of methane from intense seepage and for blowout response.
Upper ocean bubble measurements from the NE Pacific and estimates of their role in air-sea gas transfer of the weakly soluble gases nitrogen and oxygen
NASA Astrophysics Data System (ADS)
Vagle, Svein; McNeil, Craig; Steiner, Nadja
Simultaneous observations of upper-ocean bubble clouds, and dissolved gaseous nitrogen (N2) and oxygen (O2) from three winter storms are presented and analyzed. The data were collected on the Canadian Surface Ocean Lower Atmosphere Study (C-SOLAS) mooring located near Ocean Station Papa (OSP) at 50¯N, 145¯W in the NE Pacific during winter of 2003/2004. The bubble field was measured using an upward looking 200 kHz echosounder. Direct estimates of bubble mediated gas fluxes were made using assumed bubble size spectra and the upward looking echosounder data. A one-dimensional biogeochemical model was used to help compare data and various existing models of bubble mediated air-sea gas exchange. The direct bubble flux calculations show an approximate quadratic/cubic dependence on mean bubble penetration depth. After scaling from N2/O2 to carbon dioxide, near surface, nonsupersaturating, air-sea transfer rates, KT, for U10 > 12 m s-1 fall between quadratic and cubic relationships. Estimates of the subsurface bubble induced air injection flux, VT, show an approximate quadratic/cubic dependence on mean bubble penetration depth. Both KT and VT are much higher than those measured during Hurricane Frances over the wind speed range 12 < U10 < 23 m s-1. This result implies that over the open ocean and this wind speed range, older and more developed seas which occur during winter storms are more effective in exchanging gases between the atmosphere and ocean than younger less developed seas which occur during the rapid passage of a hurricane.
Hot Gas in Wolf-Rayet Bubbles. I. XMM-Newton Observations of S 308
NASA Astrophysics Data System (ADS)
Chu, Y.-H.; Guerrero, M. A.; Gruendl, R. A.; Garcia-Segura, G.; Wendker, H.
S 308 is a circumstellar bubble blown by the fast wind of the Wolf-Rayet star HD 50896. Diffuse X-ray emission from its interior has been previously detected by ROSAT; however, a significant fraction of the diffuse emission was occulted by the PSPC window support structure, making it difficult to determine the distribution of X-ray emission. Spectral analysis is also difficult because of its low surface brigthness and contamination by point sources. We have obtained XMM-Newton observations of the northewest quadrant of S 308 with 10'' resolution. The exposure time was 47 ks, but a high-background flare occurred during the observation and limited the useful exposure times to 22.7 ks and 16.9 ks for the EPIC/MOS and EPIC/pn observations, respectively. Even with reduced exposures, diffuse X-ray emission from S 308 was clearly detected. The X-ray emission shows a limb-brightened morphology; however, a distinct gap with widths of 100--200'' (0.7--1.4 pc) exists between the optical shell rim and the outer edge of the diffuse X-ray emission. This is in sharp contrast to NGC 6888, in which the X-ray emission extends all the way to the edge of the optical shell. The integrated X-ray spectrum of S 308 is soft, showing prominent N vii lines which reflect the enhanced N abundance in the nebula. Spectral fits with thin plasma model indicate that the hot gas in S 308 has a temperature of T 1.1*E6 K (kT 0.094 keV). This temperature is lower than those of NGC 6888 and planetary nebulae, 2--3x106 K. The differences in morphology and plasma temperature between S 308 and NGC 6888 may be attributed to an evolutionary effect, as S 308 is 70,000 yr old and NGC 6888 is only 24,000 yr old.
Physical Processes for Single Bubble Sonoluminescence
Ho-Young Kwak; Jung Hee Na
Analytic solutions for a sonoluminescing gas bubble have been obtained, which provide density, pressure and temperature distributions for the gas inside bubble oscillating under ultrasonic field. The solutions have revealed that sonoluminescence should occur just prior to the bubble collapse and its duration is less than 300 ps and that increase and subsequent rapid decrease in bubble wall acceleration induce
The accuracy of the bubble meter method for gas flow measurements
A. Levy
The bubble meter technique is an absolute method of measuring the volume flow rate of gases. It requires accurate standards of mass and time only and is simple in application. This paper describes the method, examines its potential accuracy and derives criteria for design. It is found that errors may be kept below Ý1% for flows between 0.1 and 1000
Determination of the Accommodation Coefficient Using Vapor/gas Bubble Dynamics in an Acoustic Field
NASA Technical Reports Server (NTRS)
Gumerov, Nail A.; Hsiao, Chao-Tsung; Goumilevski, Alexei G.; Allen, Jeff (Technical Monitor)
Nonequilibrium liquid/vapor phase transformations can occur in superheated or subcooled liquids in fast processes such as in evaporation in a vacuum. The rate at which such a phase transformation occurs depends on the "condensation" or "accommodation" coefficient, Beta, which is a property of the interface. Existing measurement techniques for Beta are complex and expensive. The development of a relatively inexpensive and reliable technique for measurement of Beta for a wide range of substances and temperatures is of great practical importance. The dynamics of a bubble in an acoustic field strongly depends on the value of Beta. It is known that near the saturation temperature, small vapor bubbles grow under the action of an acoustic field due to "rectified heat transfer." This finding can be used as the basis for an effective measurement technique of Beta. We developed a theory of vapor bubble behavior in an isotropic acoustic wave and in a plane standing acoustic wave. A numerical code was developed which enables simulation of a variety of experimental situations and accurately takes into account slowly evolving temperature. A parametric study showed that the measurement of Beta can be made over a broad range of frequencies and bubble sizes. We found several interesting regimes and conditions which can be efficiently used for measurements of Beta. Measurements of Beta can be performed in both reduced and normal gravity environments.
Shock-induced collapse of a gas bubble in shockwave lithotripsy Eric Johnsena
Dabiri, John O.
Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125: a re-entrant jet forms in the direction of propagation of the pulse and penetrates the bubble during by the formation of a re-entrant jet,11 and shockwaves are generated when the jet impacts the distal side, which
Methane isotopic signature of gas bubbles in permafrost winter lake ice: a tool for quantifying variable oxidation levels
NASA Astrophysics Data System (ADS)
Sapart, C. J.; Boereboom, T.; Roeckmann, T.; Tison, J.-L.
Methane (CH4) is a strong greenhouse gas and its atmospheric mixing ratio has strongly increased since pre-industrial times. This increase was primarily due to emissions from anthropogenic sources, but there is growing concern about possible feedbacks of natural sources in a changing climate. Thawing of permafrost areas in the Arctic is considered as an important feedback, since the Arctic region undergoes the fastest climate change and hosts large carbon stocks. Subarctic lakes are considered as "hotspots" for CH4 emissions, but the role of the ice cover during the winter period is not well understood to date. Here, we present measurements of CH4 mixing ratio and ?13C-CH4 in 4 types of bubbles identified in subarctic lake ice covers located in a sporadic or discontinuous permafrost area. Our analysis reveals that different bubble types contain CH4 with different, specific isotopic signatures. The evolution of mixing ratio and ?13C-CH4 suggest that oxidation of dissolved CH4 is the most important process determining the isotopic composition of CH4 in bubbles. This results from gas exsolution occurring during the ice growth process. A first estimate of the CH4 oxidation budget (mean = 0.12 mg CH4 m-2 d-1) enables to quantify the impact of the ice cover on CH4 emissions from subartic lakes. The increased exchange time between gases coming from the sediments and the water column, due to the capping effect of the lake ice cover, reduces the amount of CH4 released "as is" and favours its oxidation into carbon dioxide; the latter being further added to the HCO3- pool through the carbonate equilibration reactions.
The effect of a micro bubble dispersed gas phase on hydrogen isotope transport in liquid metals under nuclear irradiation
Fradera, Jorge
The present work intend to be a first step towards the understanding and quantification of the hydrogen isotope complex phenomena in liquid metals for nuclear technology. Liquid metals under nuclear irradiation in,e.g., breeding blankets of a nuclear fusion reactor would generate tritium which is to be extracted and recirculated as fuel. At the same time that tritium is bred, helium is also generated and may precipitate in the form of nano bubbles. Other liquid metal systems of a nuclear reactor involve hydrogen isotope absorption processes, e.g., tritium extraction system. Hence, hydrogen isotope absorption into gas bubbles modelling and control may have a capital importance regarding design, operation and safety. Here general models for hydrogen isotopes transport in liquid metal and absorption into gas phase, that do not depend on the mass transfer limiting regime, are exposed and implemented in OpenFOAMR CFD tool for 0D to 3D simulations. Results for a 0D case show the impact of a He dispersed phase of na...
Ultraviolet absorption by interstellar gas near the LMC star HD 36402 in the interstellar bubble N51D
NASA Technical Reports Server (NTRS)
De Boer, K. S.; Nash, A. G.
Four interstellar absorption components associated with the immediate surroundings of the star are found in UV, high-dispersion IUE spectra of the LMC star HD 36402 in the N51D nebulosity. The 305 km/sec absorption is found to originate in low-density, 10,000 K gas, and the density and velocity structures agree with that derived from visual emission lines. From a fit of the observed Lyman-alpha profile, it is found that there is an N(H) of about 10 to the 20.2/sq cm in front of HD 36402, while the large N(H) of approximately 10 to the 21.3/sq cm from 21-cm data indicates most of the neutral gas to be behind N51D. An additional component shows N V, C IV and Si IV features which are stronger than is consistent with a wind-blown interstellar bubble, implying that there is additional absorption outside the bubble. Solar abundance ratios for the metals are suggested by the overall pattern of absorption line strength.
Renegotiation Without Holdup: Anticipating Spending and Infrastructure Concessions
Eduardo Engel; Ronald Fischer; Alexander Galetovic
Infrastructure concessions are frequently renegotiated after investments are sunk, resulting in better contractual terms for the franchise holders. This paper offers a political economy explanation for renegotiations that occur with no apparent holdup. We argue that they are used by political incumbents to anticipate infrastructure spending and thereby increase the probability of winning an upcoming election. Contract renegotiations allow administrations
Patent Holdup and Royalty Stacking* Mark A. Lemley**
Sadoulet, Elisabeth
Patent Holdup and Royalty Stacking* Mark A. Lemley** & Carl Shapiro*** We study several interconnected problems that arise under the current U.S. patent system when a patent covers one component using bargaining theory that the threat to obtain a permanent injunction greatly enhances the patent
Liquid holdup and flow dispersion in zeolite packed beds
V. J. Inglezakis; M. Lemonidou; H. P. Grigoropoulou
A simple tracing method, based on residence time distribution measurements, is presented for the evaluation of the liquid holdup and dispersion in zeolite packed beds. Two tracers and two different materials, one porous (zeolite clinoptilolite) and one non-porous (SiC), were used in experiments on seven packed beds of different dimensions, operating under downflow or upflow condition, in the range of
O'keefe, J A; Lowman, P D; Dunning, K L
Spectroscopic analysis of light produced by electrodeless discharge in a tektite bubble showed the main gases in the bubble to be neon, helium, and oxygen. The neon and helium have probably diffused in from the atmosphere, while the oxygen may be atmospheric gas incorporated in the tektite during its formation. PMID:17801113
NSDL National Science Digital Library
In this math lesson, learners practice measurement skills as they examine a soap bubble print. Learners follow a recipe to make a soap bubble solution. They use the soapy solution to blow large bubbles with a plastic drinking straw until the bubbles pop, leaving behind circular prints. Learners find the diameter, circumference, and area of the bubble print.
Influence of a gas bubble on the dynamical parameters of the slug flow using particle image velocimetry
NASA Astrophysics Data System (ADS)
Siddiqui, M. I.; Heikal, M. R.; Munir, S.; Dass, S. C.; Aziz, A. Rashid A.
Inlet conditions strongly affect the dynamical parameters of a two-phase slug flow. A series of experiments were carried out, in a 6m long Plexiglas pipe having internal diameter 74 mm, to investigate the influence of gas bubble on the flow dynamics inside the slugy body of a unit slug. The pipe was kept inclined at an elevation of 1.160 to consider the terrain slugging mechanism. An optical diagnostic technique, Particle Image Velocimetry (PIV) was employed at a point 3.5m from the inlet to measure the instantaneous velocity fields of the flow for each case. Single-phase liquid pipe flow and the slugy body of the two-phase slug flow are the targeted sections for study and comparison. Velocity components, turbulence intensity and average volume flux are measured and compared. The effect of gas bubble on the liquid Reynolds number is also considered. It is noticed that by increasing the gas flow rate velocity, average flux and average kinetic energy increases dramatically in a slugy body of a slug flow regime. The results are also compared with the single phase liquid flow having same liquid flow rate. Moreover it is noticed that the increase in average volume flux in a slugy body for lower liquid flow rates are more significant as compared to the higher liquid flow rates by increasing gas rate. This shows that slug can be helpful in oil transportation in terrain oil fields for lower liquid flow rates as it creates more fluctuations and vibrational forces for higher liquid flow.
Bubble columns for condensation at high concentrations of noncondensable gas: Heat-transfer model and experiments
Narayan, G. Prakash
Carrier gas based thermodynamic cycles are common in water desalination applications. These cycles often require condensation of water vapor out of the carrier gas stream. As the carrier gas is most likely a noncondensable ...
Sonoluminescing Air Bubbles Rectify Argon
Detlef Lohse; Michael P. Brenner; Todd F. Dupont; Sascha Hilgenfeldt; Blaine Johnston
The dynamics of single bubble sonoluminescence (SBSL) strongly depends on the percentage of inert gas within the bubble. We propose a theory for this dependence, based on a combination of principles from sonochemistry and hydrodynamic stability. The nitrogen and oxygen dissociation and subsequent reaction to water soluble gases implies that strongly forced air bubbles eventually consist of pure argon. Thus
Phase Diagrams for Sonoluminescing Bubbles
Sascha Hilgenfeldt; Detlef Lohse; Michael P. Brenner
Sound driven gas bubbles in water can emit light pulses. This phenomenon is called sonoluminescence (SL). Two different phases of single bubble SL have been proposed: diffusively stable and diffusively unstable SL. We present phase diagrams in the gas concentration vs forcing pressure state space and also in the ambient radius vs gas concentration and vs forcing pressure state spaces.
6/10/12 Technique Devised to Measure Pipeline Gas Bubbles | Science Business 1/2sciencebusiness.technewslit.com/?p=9481
Sµbester, AndrÃs
of the blow out preventer was a key factor in the extensive damage caused by the BP/Deepwater Horizon oil for Oil and Gas Eight Teams Funded for Research on Gulf Oil Spill Impact * * * NEW PRODUCTS ENGINEERING issue in extracting oil with off-shore oil rigs. When these bubbles are brought up from the seabed
AFM forces between mica and polystyrene surfaces in aqueous electrolyte solutions with and without gas bubbles.
Saavedra, Jorge H; Acuþa, Sergio M; Toledo, Pedro G
Force curves between a flat mica substrate and a polystyrene microsphere were measured with an atomic force microscope (AFM) in carefully degassed water and aqueous NaCl, CaCl2, and AlCl3 solutions. The pH of the water used does not change significantly with degassing treatment, and its value remains close to 6. Electrolyte concentration ranges from 10-4 to 10-2M and pH from 4.7 to 5.1. We have found that the repulsive long-range electrostatic force between mica and polystyrene is attenuated by the presence of electrolytes and counterbalanced by a long-range attractive force, which we referred to as a hydrophobic force, which is longer-ranged than the ever present attractive van der Waals force. This force, which includes the adhesive bridging of residual air bubbles and newborn vapor cavities, and any other unknown forces, is reasonably well represented by a unique exponential law. Prefactor and decaying length are not very sensitive to electrolyte type, concentration, and pH, suggesting that any new force included in the law, in addition to adhesive bridges, should obey a non-classical electrostatic mechanism. However, we also know that liquid/solid contact angle and liquid/vapor surface tension increase with electrolyte concentration and valence increasing the stability of bubbles and cavities which in turn increase the bridging force. Clearly, these effects are hidden in the empirical force law. PMID:23998373
Sonochemistry and bubble dynamics.
Mettin, Robert; Cairµs, Carlos; Troia, Adriano
The details of bubble behaviour in chemically active cavitation are still not sufficiently well understood. Here we report on experimental high-speed observations of acoustically driven single-bubble and few-bubble systems with the aim of clarification of the connection of their dynamics with chemical activity. Our experiment realises the sonochemical isomerization reaction of maleic acid to fumaric acid, mediated by bromine radicals, in a bubble trap set-up. The main result is that the reaction product can only be observed in a parameter regime where a small bubble cluster occurs, while a single trapped bubble stays passive. Evaluations of individual bubble dynamics for both cases are given in form of radius-time data and numerical fits to a bubble model. A conclusion is that a sufficiently strong collapse has to be accompanied by non-spherical bubble dynamics for the reaction to occur, and that the reason appears to be an efficient mixing of liquid and gas phase. This finding corroborates previous observations and literature reports on high liquid phase sonochemical activity under distinct parameter conditions than strong sonoluminescence emissions. PMID:25194210
Cumulative Innovation, Sampling and the Hold-Up Problem
Rufus Pollock
With cumulative innovation and imperfect information about the value of innovations, intellectual property rights can result in hold-up and therefore it may be better not to have them. Extending the basic cumulative innovation model to include 'sampling' by second-stage firms, we find that the lower the cost of sampling, or the larger the differential between high and low value second-stage
Wildeman, Sander; Lhuissier, Henri; Sun, Chao; Lohse, Detlef; Prosperetti, Andrea
We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rubbing force and velocity exceed a certain threshold. Direct observation through a transparent solid shows that each bubble in the trail results from the early coalescence of several microscopic bubbles, themselves detaching from microscopic gas pockets forming between the solids. From a detailed study of the wear tracks, with atomic force and scanning electron microscopy imaging, we conclude that these microscopic gas pockets originate from a local fracturing of the surface asperities, possibly enhanced by chemical reactions at the freshly created surfaces. Our findings will be useful either for preventing undesired bubble formation or, on the contrary, for writing with bubbles, i.e., creating controlled patterns of microscopic bubbles. PMID:24982169
Wildeman, Sander; Lhuissier, Henri; Sun, Chao; Lohse, Detlef; Prosperetti, Andrea
We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rubbing force and velocity exceed a certain threshold. Direct observation through a transparent solid shows that each bubble in the trail results from the early coalescence of several microscopic bubbles, themselves detaching from microscopic gas pockets forming between the solids. From a detailed study of the wear tracks, with atomic force and scanning electron microscopy imaging, we conclude that these microscopic gas pockets originate from a local fracturing of the surface asperities, possibly enhanced by chemical reactions at the freshly created surfaces. Our findings will be useful either for preventing undesired bubble formation or, on the contrary, for "writing with bubbles," i.e., creating controlled patterns of microscopic bubbles. PMID:24982169
Sound propagation in water containing large tethered spherical encapsulated gas bubbles with resonance frequencies in the 50 Hz to 100 Hz range.
Lee, Kevin M; Hinojosa, Kevin T; Wochner, Mark S; Argo, Theodore F; Wilson, Preston S; Mercier, Richard S
The efficacy of large tethered encapsulated gas bubbles for the mitigation of low frequency underwater noise was investigated with an acoustic resonator technique. Tethered latex balloons were used as the bubbles, which had radii of approximately 5 cm. Phase speeds were inferred from the resonances of a water and balloon-filled waveguide approximately 1.8 m in length. The Commander and Prosperetti effective-medium model [J. Acoust. Soc. Am. 85, 732-746 (1989)] quantitatively described the observed dispersion from well below to just below the individual bubble resonance frequency, and it qualitatively predicted the frequency range of high attenuation for void fractions between 2% and 5% for collections of stationary balloons within the waveguide. A finite-element model was used to investigate the sensitivity of the waveguide resonance frequencies, and hence the inferred phase speeds, to changes in individual bubble size and position. The results indicate that large tethered encapsulated bubbles could be used mitigate low frequency underwater noise and that the Commander and Prosperetti model would be useful in the design of such a system. PMID:22088005
Review of Current Literature and Research on Gas Supersaturation and Gas Bubble Trauma: Special Publication Number 1, 1986.
Colt, John; Bouck, Gerald R.; Fidler, Larry
This report presents recently published information and on-going research on the various areas of gas supersaturation. Growing interest in the effects of chronic gas supersaturation on aquatic animals has been due primarily to heavy mortality of salmonid species under hatchery conditions. Extensive examination of affected animals has failed to consistently identify pathogenic organisms. Water quality sampling has shown that chronic levels of gas supersaturation are commonly present during a significant period of the year. Small marine fish larvae are significantly more sensitive to gas supersaturation than salmonids. Present water quality criteria for gas supersaturation are not adequate for the protection of either salmonids under chronic exposure or marine fish larvae, especially in aquaria or hatcheries. To increase communication between interested parties in the field of gas supersaturation research and control, addresses and telephone numbers of all people responding to the questionnaire are included. 102 refs.
Intense gas bubble emissions in the Kerch seep area - A newly discovered high-flux seep site in the Black Sea
NASA Astrophysics Data System (ADS)
R—mer, M.; Sahling, H.; Pape, T.; Bahr, A.; Feseker, T.; Wintersteller, P.; Bohrmann, G.
More than 500 bubble-induced hydroacoustic anomalies (flares) were found in the water column above the seafloor in the study area comprising about 430 km2 at the Don-Kuban paleo-fan (Eastern Black Sea) by using ship mounted single beam and multibeam echosounders. Almost all flares originated from the seafloor above the gas hydrate stability zone (GHSZ), which in that region is located below ~700 m water depth. This observation confirms the sealing mechanism of gas hydrate, which impedes migration of free gas through the GHSZ and subsequent bubble emission from the seafloor. However, an intense seep site, called the "Kerch seep area" was discovered as an exception at 890 m water depth well within the GHSZ. In situ temperature measurements in shallow sediments indicate locally elevated temperatures probably caused by enhanced upward fluid flow. The base of the GHSZ in this region is generally situated at about 150 m below the seafloor. However, the local thermal anomalies result in a thinning of the gas hydrate occurrence zone to only a few meters below the seafloor and allow free gas to reach the seafloor. At sites where gas migrated into near-surface deposits, shallow gas hydrate deposits evolved and up-doming of overlying sediments led to the formation of mounds rising several meters from the surrounding seafloor. Further gas bubbles ascending from greater depth are accumulated below the gas hydrate layer at the base of the mound structures and migrate horizontally to their rims. At the mound edges gas bubbles either might form fresh gas hydrates and increase the extent of the mound structures by pushing up overlying sediments or escape at several sites into the water column. Two mounds were mapped in ultra-high resolution during dives with the autonomous underwater vehicle 'AUV MARUM SEAL 5000'. Several individual flares were detected in the Kerch seep area using hydroacoustic systems. Repeated surveys in that area conducted during three cruises within four years suggested that gas discharge varied spatially and temporally while the total number of flares remained rather constant. During seafloor inspections with MARU?s remotely operated vehicle 'ROV QUEST 4000 m' gas bubble emission sites were investigated in detail. Gas bubbles collected during the ROV dives mainly consisted of methane predominantly of microbial origin. By analyzing the high-definition video material the gas flux from several bubble emission sites was calculated. In combination with the hydroacoustic results (flare distributions) it is estimated that about 2.2 - 87 æ 106 mol CH4/yr are emitted from the seafloor at the Kerch seep area. Despite this high mass of methane injected into the hydrosphere, the peak of the highest flares at ~350 m water depth as revealed by echosounder recording suggest that the ascending methane completely dissolves in the water column and does not pass the sea-atmosphere boundary.
Fluid Dynamics of Bubbly Liquids
NASA Technical Reports Server (NTRS)
Tsang, Y. H.; Koch, D. L.; Zenit, R.; Sangani, A.; Kushch, V. I.; Spelt, P. D. M.; Hoffman, M.; Nahra, H.; Fritz, C.; Dolesh, R.
Experiments have been performed to study the average flow properties of inertially dominated bubbly liquids which may be described by a novel analysis. Bubbles with high Reynolds number and low Weber number may produce a fluid velocity disturbance that can be approximated by a potential flow. We studied the behavior of suspensions of bubbles of about 1.5 mm diameter in vertical and inclined channels. The suspension was produced using a bank of 900 glass capillaries with inner diameter of about 100 microns in a quasi-steady fashion. In addition, salt was added to the suspension to prevent bubble-bubble coalescence. As a result, a nearly monodisperse suspension of bubble was produced. By increasing the inclination angle, we were able to explore an increasing amount of shear to buoyancy motion. A pipe flow experiment with the liquid being recirculated is under construction. This will provide an even larger range of shear to buoyancy motion. We are planning a microgravity experiment in which a bubble suspension is subjected to shearing in a couette cell in the absence of a buoyancy-driven relative motion of the two phases. By employing a single-wire, hot film anemometer, we were able to obtain the liquid velocity fluctuations. The shear stress at the wall was measured using a hot film probe flush mounted on the wall. The gas volume fraction, bubble velocity, and bubble velocity fluctuations were measured using a homemade, dual impedance probe. In addition, we also employed a high-speed camera to obtain the bubble size distribution and bubble shape in a dilute suspension. A rapid decrease in bubble velocity for a dilute bubble suspension is attributed to the effects of bubble-wall collisions. The more gradual decrease of bubble velocity as gas volume fraction increases, due to subsequent hindering of bubble motion, is in qualitative agreement with the predictions of Spelt and Sangani for the effects of potential-flow bubble-bubble interactions on the mean velocity. The ratio of the bubble velocity variance to the square of the mean is 0(0.1). For these conditions Spelt and Sangani predicted that the homogeneous suspension would be unstable and clustering into horizontal rafts will take place. Evidence for bubble clustering is obtained by analysis of video images. The liquid velocity variance is larger than would be expected for a homogeneous suspension and the liquid velocity frequency spectrum indicates the presence of velocity fluctuations that are slow compared with the time for the passage of an individual bubble. These observations provide further evidence for bubble clustering.
NSDL National Science Digital Library
What keeps bubbles and other things, like airplanes, floating or flying in the air? In this activity, learners blow bubbles and wave 3x5 cards above, below and on different sides of the bubbles to keep them afloat as long as possible. The Did You Know section explains the Bernoulli principle: how waving cards above the bubbles helps keep them afloat because faster moving air exerts less pressure to push the bubbles down. The activity can be extended by having learners wave their bubbles through an obstacle course they design themselves.
A three dimensional model of an ultrasound contrast agent gas bubble and its mechanical effects on microvessels
Hosseinkhah, N.; Hynynen, K.
Ultrasound contrast agents inside a microvessel, when driven by ultrasound, oscillate and induce mechanical stresses on the vessel wall. These mechanical stresses can produce beneficial therapeutic effects but also induce vessel rupture if the stresses are too high. Therefore, it is important to use sufficiently low pressure amplitudes to avoid rupturing the vessels while still inducing the desired therapeutic effects. In this work, we developed a comprehensive three dimensional model of a confined microbubble inside a vessel while considering the bubble shell properties, blood viscosity, vessel wall curvature and the mechanical properties of the vessel wall. Two bubble models with the assumption of a spherical symmetric bubble and a simple asymmetrical bubble were simulated. This work was validated with previous experimental results and enabled us to evaluate the microbubbles behaviour and the resulting mechanical stresses induced on the vessel walls. In this study the fluid shear and circumferential stresses were evaluated as indicators of the mechanical stresses. The effects of acoustical parameters, vessel viscoelasticity and rigidity, vessel/bubble size and off-center bubbles on bubble behaviour and stresses on the vessel were investigated. The fluid shear and circumferential stresses acting on the vessel varied with time and location. As the frequency changed, the microbubble oscillated with the highest amplitude at its resonance frequency which was different from the resonance frequency of an unbound bubble. The bubble resonance frequency increased as the rigidity of a flexible vessel increased. The fluid shear and circumferential stresses peaked at frequencies above the bubbles resonance frequency. The more rigid the vessels were, the more damped the bubble oscillations. The synergistic effect of acoustic frequency and vessel elasticity had also been investigated, since the circumferential stress showed either an increasing trend or a decreasing one versus the vessel rigidity at difference acoustic frequencies. When the acoustic pressure was increased from 52 kPa to 680 kPa, the maximum bubble radius increase by 2.5 folds and the maximum shear and circumferential stress increased by 15.7 and 18.3 folds respectively. The shear stress was largest when the acoustic frequency was higher (3.25 MHz) and the ratio of the vessel radius to the bubble radius was lower. The circumferential stress was largest when the bubble wall was closer to the vessel wall. An oscillating off-center bubble forms a mushroom shape with the most damping on the points closest to the vessel wall. PMID:22252221
An inverse approach to estimate bubble-mediated air-sea gas flux from inert gas measurements
Khatiwala, Samar
as a function of wind speed. Our results indicate air injection values at high wind speeds (> 10 m s-1-sea interface commonly is parameterized as the product of a gas transfer coefficient, k, and the air-sea concentration gradient of a gas such that, Fas=-kc([C]-cpc) or Fas=-kc([C]-[C] slp eq ) (1) where [C] (mol m3
This technology assessment addresses design and evaluation of fine bubble aeration equipment. It discusses the associated gas transfer theory used as the basis for measuring water and wastewater oxygenation efficiency. Mixing requirements are also discussed. While bubble aeration...
NSDL National Science Digital Library
Learners explore three-dimensional geometric frames including cubes and tetrahedrons, as they create bubble wands with pipe cleaners and drinking straws. Then they investigate how soap film flows into a state of minimum energy when they lift the wand up from the bubble solution. Learners also see how light reflection and interference create shimmering colors in the bubbles.
NSDL National Science Digital Library
Austen Saltz
In this activity, learners experiment with creating various types of bubble solutions and testing which ingredients form longer-lasting bubbles. Learners investigate how surface tension works and the importance of using a surfactant to make bubbles. This activity includes a video about NASA astronaut Don Pettit, who used candy corn to conduct science experiments during his stint aboard the International Space Station.
Mass transfer and gas-liquid circulation in an airlift bioreactor with viscous non-Newtonian fluids
Guo-Qing Li; Shou-Zhi Yang; Zhao-Ling Cai; Jia-Yong Chen
In an internal loop airlift reactor of 55 l working volume, gas-liquid volumetric oxygen mass transfer coefficient kLa, gas holdup ?G and liquid circulation time tc were measured with the solution of carboxymethyl cellulose to simulate the performance of a reactor with highly viscous broth. Electric conductivity and oxygen probes were used to measure the local gas holdup, liquid circulation
A Simple Economic Teaching Experiment on the Hold-Up Problem
ERIC Educational Resources Information Center
Balkenborg, Dieter; Kaplan, Todd; Miller, Timothy
The hold-up problem is central to the theory of incomplete contracts. This can occur if, after making a sunk investment in a relationship, one party can be taken advantage of by the other party, leading to inefficient underinvestment. The authors describe a simple teaching experiment that illustrates the hold-up problem, and address how to
Free gas bubbles in the hydrate stability zone: evidence from CT investigation under in situ conditions
F. Abegg; J. Freitag; G. Bohrmann; W. Brueckmann; A. Eisenhauer; H. Amann; H.-J. Hohnberg
Determination of the internal structures and the fabric of natural marine gas hydrate as well as its distribution in shallow subseafloor depth was restricted because of dissociation during recovery. Investigation under in situ conditions becomes possible with a pressure coring device. The newly developed MultiAutoclaveCorer (MAC) can take up to four cores which are housed in a pressure vessel called
Silent bubbles - Their effects and detection
NASA Technical Reports Server (NTRS)
Powell, Michael R.
This paper discusses the concept of the 'silent bubble' (a phenomenon due to gas phase formation in tissues, which does not lead to frank decompression sickness). Special attention is given to the conditions for silent bubbles formation, the methods of their detecton, and to their pathophysiology. Data relating the gas formation in blood and the symptoms of decompression sickness indicate that the distinction between the silent bubbles and clinical ones is often vague and that a bubble-free decompression never existed.
Removal of elemental mercury from flue gas by thermally activated ammonium persulfate in a bubble column reactor.
Liu, Yangxian; Wang, Qian
In this article, a novel technique on removal of elemental mercury (Hg(0)) from flue gas by thermally activated ammonium persulfate ((NH4)(2)S(2)O(8)) has been developed for the first time. Some experiments were carried out in a bubble column reactor to evaluate the effects of process parameters on Hg(0) removal. The mechanism and kinetics of Hg(0) removal are also studied. The results show that the parameters, (NH4)(2)S(2)O(8) concentration, activation temperature and solution pH, have significant impacts on Hg(0) removal. The parameters, Hg(0), SO2 and NO concentration, only have small effects on Hg(0) removal. Hg(0) is removed by oxidations of (NH4)(2)S(2)O(8), sulfate and hydroxyl free radicals. When (NH4)(2)S(2)O(8) concentration is more than 0.1 mol/L and solution pH is lower than 9.71, Hg(0) removal by thermally activated (NH4)(2)S(2)O(8) meets a pseudo-first-order fast reaction with respect to Hg(0). However, when (NH4)(2)S(2)O(8) concentration is less than 0.1 mol/L or solution pH is higher than 9.71, the removal process meets a moderate speed reaction with respect to Hg(0). The above results indicate that this technique is a feasible method for emission control of Hg(0) from flue gas. PMID:25251199
Shanahan, Martin E. R.; Sefiane, Khellil
We demonstrate that thermocapillary forces may drive bubbles against liquid flow in anomalous' mixtures. Unlike ordinary' liquids, in which bubbles migrate towards higher temperatures, we have observed vapour bubbles migrating towards lower temperatures, therefore against the flow. This unusual behaviour may be explained by the temperature dependence of surface tension of these binary mixtures. Bubbles migrating towards their equilibrium position follow an exponential trend. They finally settle in a stationary position just downstream' of the minimum in surface tension. The exponential trend for bubbles in anomalous' mixtures and the linear trend in pure liquids can be explained by a simple model. For larger bubbles, oscillations were observed. These oscillations can be reasonably explained by including an inertial term in the equation of motion (neglected for smaller bubbles). PMID:24740256
Gas-bubble snap-off under pressure driven flow in constricted noncircular capillaries
Kovscek, A.R.; Radke, C.J.
A model for snap-off of a gas thread in a constricted cornered pore is developed. The time for wetting liquid to accumulate at a pore throat into an unstable collar is examined, as for the resulting pore-spanning lens to be displaced from the pore so that snap-off is the time may repeat. A comer-flow hydrodynamic analysis for the accumulation rate of wetting liquid due to both gradients in interfacial curvature and in applied liquid-phase pressure reveals that wetting-phase pressure gradients significantly increase the frequency of liquid accumulation for snap-off as compared to liquid rearrangement driven only by differences in pore-wall curvature. For moderate and large pressure gradients, the frequency of accumulation increases linearly with pressure gradient because of the increased rate of wetting liquid flow along pore comers. Pore topology is important to the theory, for pores with relatively small throats connected to large bodies demonstrate excellent ability to snapoff gas threads even when the initial capillary pressure is high or equivalently when the liquid saturation is low. A macroscopic momentum balance across the lens resulting from snap-off reveals that lens displacement rates are not linear with the imposed pressure drop. Instead, the frequency of lens displacement scales with powers between 0.5 and 0.6 for pores with dimensionless constriction radii between 0.15 and 0.40. Statistical percolation arguments are employed to form a generation rate expression and connect pore-level foam generation events to macroscopic pressure gradients in porous media. The rate of foam generation by capillary snap-off increases linearly with the liquid-phase pressure gradient and according to a power-law relationship with respect to the imposed gas-phase pressure gradient.
Heat transfer and hydrodynamic investigations of a baffled slurry bubble column
NASA Astrophysics Data System (ADS)
Saxena, S. C.; Chen, Z. D.
Heat transfer and hydrodynamic investigations have been conducted in a 0.108 m internal diameter bubble column at ambient conditions. The column is equipped with seven 19mm diameter tubes arranged in an equilateral triangular pitch of 36.5 mm. A Monsanto synthetic heat transfer fluid, Therminol-66 having a viscosity of 39.8 cP at 303 K, is used as a liquid medium. Magnetite powders, average diameters 27.7 and 36.6 çm, in five concentrations up to 50 weight percent in the slurry, are used. As a gas phase, industrial grade nitrogen of purity 99.6 percent is employed. Gas holdup in different operating modes and regimes have been measured for the two- and three-phase systems over a superficial gas velocity range up to 0.20 m/s in the semi-batch mode. Heat transfer coefficients are measured at different tube locations in the bundle at different radial and vertical locations over a range of operating conditions. All these data are compared with the existing literature correlations and models. New correlations are proposed.
Mesoscale Benchmark Demonstration Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing
Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert; Gao, Fei; Sun, Xin; Tonks, Michael; Biner, Bullent; Millet, Paul; Tikare, Veena; Radhakrishnan, Balasubramaniam; Andersson , David
A study was conducted to evaluate the capabilities of different numerical methods used to represent microstructure behavior at the mesoscale for irradiated material using an idealized benchmark problem. The purpose of the mesoscale benchmark problem was to provide a common basis to assess several mesoscale methods with the objective of identifying the strengths and areas of improvement in the predictive modeling of microstructure evolution. In this work, mesoscale models (phase-field, Potts, and kinetic Monte Carlo) developed by PNNL, INL, SNL, and ORNL were used to calculate the evolution kinetics of intra-granular fission gas bubbles in UO2 fuel under post-irradiation thermal annealing conditions. The benchmark problem was constructed to include important microstructural evolution mechanisms on the kinetics of intra-granular fission gas bubble behavior such as the atomic diffusion of Xe atoms, U vacancies, and O vacancies, the effect of vacancy capture and emission from defects, and the elastic interaction of non-equilibrium gas bubbles. An idealized set of assumptions was imposed on the benchmark problem to simplify the mechanisms considered. The capability and numerical efficiency of different models are compared against selected experimental and simulation results. These comparisons find that the phase-field methods, by the nature of the free energy formulation, are able to represent a larger subset of the mechanisms influencing the intra-granular bubble growth and coarsening mechanisms in the idealized benchmark problem as compared to the Potts and kinetic Monte Carlo methods. It is recognized that the mesoscale benchmark problem as formulated does not specifically highlight the strengths of the discrete particle modeling used in the Potts and kinetic Monte Carlo methods. Future efforts are recommended to construct increasingly more complex mesoscale benchmark problems to further verify and validate the predictive capabilities of the mesoscale modeling methods used in this study.
Growth and setting of gas bubbles in a viscoelastic matrix imaged by X-ray microtomography: the evolution of cellular structures in fermenting wheat flour dough.
Turbin-Orger, A; Babin, P; Boller, E; Chaunier, L; Chiron, H; Della Valle, G; Dendievel, R; RÕguerre, A L; Salvo, L
X-ray tomography is a relevant technique for the dynamic follow-up of gas bubbles in an opaque viscoelastic matrix, especially using image analysis. It has been applied here to pieces of fermenting wheat flour dough of various compositions, at two different voxel sizes (15 and 5 ?m). The resulting evolution of the main cellular features shows that the creation of cellular structures follows two regimes that are defined by a characteristic time of connectivity, tc [30 and 80 min]: first (t ? tc), bubbles grow freely and then (t ? tc) they become connected since the percolation of the gas phase is limited by liquid films. During the first regime, bubbles can be tracked and the local strain rate can be measured. Its values (10(-4)-5 æ 10(-4) s(-1)) are in agreement with those computed from dough viscosity and internal gas pressure, both of which depend on the composition. For higher porosity, P = 0.64 in our case, and thus occurring in the second regime, different cellular structures are obtained and XRT images show deformed gas cells that display complex shapes. The comparison of these images with confocal laser scanning microscopy images suggests the presence of liquid films that separate these cells. The dough can therefore be seen as a three-phase medium: viscoelastic matrix/gas cell/liquid phase. The contributions of the different levels of matter organization can be integrated by defining a capillary number (C = 0.1-1) that makes it possible to predict the macroscopic dough behavior. PMID:25816111
Sonoluminescing bubbles and mass diffusion
Ritva L—fstedt; Keith Weninger; Seth Putterman; Bradley P. Barber
The transduction of sound into light by a pulsating bubble in water occurs when its maximum radius is about ten times greater than its ambient radius. For such high-amplitude motion, the steady-state balance of mass flow between the bubble and gas dissolved in the surrounding fluid can be maintained by diffusion only at low partial pressures, about 3 Torr. The
Enhancing gas-liquid mass transfer rates in non-newtonian fermentations by confining mycelial growth to microbeads in a bubble column
Gbewonyo, K.; Wang, D.I.C.
The performance of a penicillin fermentation was assessed in a laboratory-scale bubble column fermentor, with mycelial growth confined to the pore matrix of celite beads. Final cell densities of 29 g/L and penicillin titres of 5.5 g/L were obtained in the confined cell cultures. In comparison, cultures of free mycelial cells grown in the absence of beads experienced dissolved oxygen limitations in the bubble column, giving only 17 g/L final cell concentrations with equally low penicillin titres of 2 g/L. The better performance of the confined cell cultures was attributed to enhanced gas liquid mass transfer rates, with mass transfer coefficients (k /SUB L/ a) two to three times higher than those determined in the free cell cultures. Furthermore, the confined cell cultures showed more efficient utilization of power input for mass transfer, providing up to 50% reduction in energy requirements for aeration.
NSDL National Science Digital Library
How do you measure a bubble when it's floating? You can't really, but in this activity, learners can measure the diameter of the ring of suds a bubble leaves on a flat surface. The fun is blowing up the bubbles as big as possible with a straw. Then comes the measuring. This activity can be used to connect science and math, and makes a great rainy day or indoor lunch activity.
25 July 2002 Sonoluminescence: Bubble power
Suslick, Kenneth S.
25 July 2002 Sonoluminescence: Bubble power When a gas bubble in a liquid is excited by ultrasonic. These flashes of light, known as 'sonoluminescence', occur as the bubble implodes, or cavitates. Now DidenkoÙ397 (2002); doi:10.1038/nature00895 | First Paragraph | Full Text (HTML / PDF) | Sonoluminescence: Inside
Mechanisms for stable single bubble sonoluminescence
Brenner, M.P. [Department of Mathematics, MIT, Cambridge, Massachusetts 02139 (United States)] [Department of Mathematics, MIT, Cambridge, Massachusetts 02139 (United States); Lohse, D. [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany)] [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany); [Department of Mathematics, The University of Chicago, Chicago, Illinois 60637 (United States); Oxtoby, D. [Department of Chemistry and James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Chemistry and James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Dupont, T.F. [Department of Mathematics, The University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Mathematics, The University of Chicago, Chicago, Illinois 60637 (United States)
A gas bubble trapped in water by an oscillating acoustic field is expected to either shrink or grow on a diffusive time scale, depending on the forcing strength and the bubble size. At high ambient gas concentration this has long been observed. However, recent sonoluminescence experiments show that when the ambient gas concentration is low the bubble can be stable for days. This paper discusses mechanisms leading to stability. {copyright} {ital 1996 The American Physical Society.}
Ammonia absorption from a bubble expanding at a submerged orifice into water
Koichi Terasaka; Junko Oka; Hideki Tsuge
To investigate the mechanism of gas absorption from a bubble containing soluble and insoluble components, a gaseous mixture of ammonia and nitrogen was bubbled into water. The growth curve, volume, surface area and shape of the growing bubbles were measured with parameters such as inlet gas composition, gas flow rate and gas chamber volume. The bubble volume decreased with the
NASA Technical Reports Server (NTRS)
2007-01-01In this processed Spitzer Space Telescope image, baby star HH 46/47 can be seen blowing two massive 'bubbles.' The star is 1,140 light-years away from Earth. The infant star can be seen as a white spot toward the center of the Spitzer image. The two bubbles are shown as hollow elliptical shells of bluish-green material extending from the star. Wisps of green in the image reveal warm molecular hydrogen gas, while the bluish tints are formed by starlight scattered by surrounding dust. These bubbles formed when powerful jets of gas, traveling at 200 to 300 kilometers per second, or about 120 to 190 miles per second, smashed into the cosmic cloud of gas and dust that surrounds HH 46/47. The red specks at the end of each bubble show the presence of hot sulfur and iron gas where the star's narrow jets are currently crashing head-on into the cosmic cloud's gas and dust material. Whenever astronomers observe a star, or snap a stellar portrait, through the lens of any telescope, they know that what they are seeing is slightly blurred. To clear up the blurring in Spitzer images, astronomers at the Jet Propulsion Laboratory developed an image processing technique for Spitzer called Hi-Res deconvolution. This process reduces blurring and makes the image sharper and cleaner, enabling astronomers to see the emissions around forming stars in greater detail. When scientists applied this image processing technique to the Spitzer image of HH 46/47, they were able to see winds from the star and jets of gas that are carving the celestial bubbles. This infrared image is a three-color composite, with data at 3.6 microns represented in blue, 4.5 and 5.8 microns shown in green, and 24 microns represented as red.
Numerical simulations of single bubble sonoluminescence
Mourad, P.D. (Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98195 (United States)); Marcus, D.L. (Lawrence Livermore Natl. Lab., Livermore, CA 94551 (United States)); Roy, R.A.; Matula, T.J. (Univ. of Washington, Seattle, WA 98195 (United States))
A higher-order Godunov method is used to solve the spherically symmetric, compressible Euler equations with an ideal gas equation of state as a model for single bubble sonoluminescence. Basic shock physics is discussed in this context, exploring how modeled variations of the bubble interior support or suppress the generation and propagation of shock waves within the bubble as well as the interaction of a shock with the bubble interface. [Work supported by ONR through the ONR/ARL program.
Multicompartment hydrodynamic model for slurry bubble columns
Ion Iliuta; Damien Desvigne; JÕr¶me Anfray; Nicolas Dromard; Daniel Schweich
A core-annulus multicompartment two-dimensional two-bubble class model accounting for slurry recirculation and coupled with catalyst transport was developed as a part and parcel of the analysis of the behavior of slurry bubble column reactors at high gas throughputs corresponding to the churn turbulent flow regime. The model analyzed the contributions of bubble-induced turbulence closures, bubble coalescence and breakup phenomena, and
NSDL National Science Digital Library
In this activity on page 15 of the PDF, learners measure the amount of bubbles that they make using a detergent. Learners investigate whether adding Epsom salt to the solution affects its "sudsiness"--an important attribute of soap, since sudsy bubbles help soap clean greasy dirt. Use this activity to explore how chemicals can change a material's properties and how substances dissolve.
NSDL National Science Digital Library
The Exploratorium
In this activity, learners use simple materials to create giant bubbles. Learners will explore what gives bubbles their shape, what makes them break or last, what causes the colors and patterns in the soap film, and why do they change? Use this activity to introduce the concepts of surface tension and interference.
Gravity driven flows of bubble suspensions.
NASA Astrophysics Data System (ADS)
Zenit, Roberto; Koch, Donald L.; Sangani, Ashok K.
Experiments on vertical and inclined channels were performed to study the behavior of a mono-dispersed bubble suspension for which the dual limit of large Reynolds number and small Weber number is satisfied. A uniform stream of 1.5 mm diameter bubbles is produced by a bank of identical capillaries and coalescence is inhibited by addition of salt to the water. Measurements of the liquid velocity and bubble-probe collision rate are obtained with a hot wire anemometer. The gas volume fraction, bubble velocity, velocity variance and chord length are measured using a dual impedance probe. Image analysis is used to quantify the distributions of bubble size and aspect ratio. For vertical channels the bubble velocity is observed to decrease as the bubble concentration increases in accord with the predictions of Spelt and Sangani (1998). The bubble velocity variance arises largely due to bubble-wall and bubble-bubble collisions. For inclined channels, the strength of the shear flow is controlled by the extent of bubble segregation and the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion for a range of gas volume fractions and channel inclination angles.
NASA Technical Reports Server (NTRS)
Mattox, D. M.
Surface tension gradient in melt forces gas bubbles to surface, increasing glass strength and transparency. Conventional chemical and buoyant fining are extremely slow in viscous glasses, but tension gradient method moves 250 um bubbles as rapidly as 30 um/s. Heat required for high temperature part of melt is furnished by stationary electrical or natural-gas heater; induction and laser heating are also possible. Method has many applications in industry processes.
Biomass gasification with air in an atmospheric bubbling fluidized bed. Effect of six operational variables on the quality of the produced raw gas
Narvaez, I.; Orio, A.; Corella, J. [Univ. Complutense of Madrid (Spain). Dept. of Chemical Engineering] [Univ. Complutense of Madrid (Spain). Dept. of Chemical Engineering; Aznar, M.P. [Univ. of Saragossa (Spain). Dept. of Chemical Engineering] [Univ. of Saragossa (Spain). Dept. of Chemical Engineering
Biomass gasification with air in a bubbling fluidized bed is studied in a small pilot plant. Variables analyzed are equivalence ratio (from 0.20 to 0.45), temperatures of the gasifier bed (750--850 C) and of its freeboard (500--600 C), H/C ratio in the feed, use of secondary air (10% of the overall) in the freeboard, and addition (2--5 wt %) of a calcined dolomite mixed with the biomass used as the feedstock. Using advanced tar and gas sampling and analysis methods, the gas composition and tar content in the gas are determined and their variation with the operation parameters is given. A statistical analysis of the effects of the gasification variables is also here presented.
Sonoluminescing Air Bubbles Rectify Argon
Lohse, D.; Hilgenfeldt, S. [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany)] [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany); Brenner, M.P. [Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Dupont, T.F. [Department of Computer Science, University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Computer Science, University of Chicago, Chicago, Illinois 60637 (United States); Johnston, B. [Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States)
The dynamics of single bubble sonoluminescence (SBSL) strongly depends on the percentage of inert gas within the bubble. We propose a theory for this dependence, based on a combination of principles from sonochemistry and hydrodynamic stability. The nitrogen and oxygen dissociation and subsequent reaction to water soluble gases implies that strongly forced air bubbles eventually consist of pure argon. Thus it is the partial argon (or any other inert gas) pressure which is relevant for stability. The theory provides quantitative explanations for many aspects of SBSL. {copyright} {ital 1997} {ital The American Physical Society}
Bubble, Bubble, Toil and Trouble.
ERIC Educational Resources Information Center
Journal of Chemical Education, 2001
Bubbles are a fun way to introduce the concepts of surface tension, intermolecular forces, and the use of surfactants. Presents two activities in which students add chemicals to liquid dishwashing detergent with water in order to create longer lasting bubbles. (ASK)
Study on the dynamic holdup distribution of the pulsed extraction column
Wang, S.; Chen, J.; Wu, Q. [Tsinghua University, Beijing 100084 (China)
In the study, a CSTR cascade dynamic hydraulic model was developed to investigate the dynamic holdup distribution of the pulsed extraction column. It is assumed that the dynamic process of the dispersed phase holdup of pulsed extraction column has equal effects with the operational process of multiple cascade CSTRs. The process is consistent with the following assumptions: the holdups vary on different stages but maintain uniform on each stage; the changes of the hydraulic parameters have impact initially on the inlet of dispersed phase, and stability will be reached gradually through stage-by-stage blending. The model was tested and verified utilizing time domain response curves of the average holdup. Nearly 150 experiments were carried out with different capillary columns, various feed liquids, and diverse continuous phases and under different operation conditions. The regression curves developed by the model show a good consistency with the experimental results. After linking parameters of the model with operational conditions, the study further found that the parameters are only linearly correlated with pulse conditions and have nothing to do with flow rate for a specific pulsed extraction column. The accuracy of the model is measured by the average holdup, and the absolute error is Ý0.01. The model can provide supports for the boundary studies on hydraulics and mass transfer by making simple and reliable prediction of the dynamic holdup distribution, with relatively less accessible hydraulic experimental data. (authors)
Animation of Bubbles in Liquid
Jeong-mo Hong; Chang-hun Kim
We present a new fluid animation technique in which liquid and gas interact with each other, using the example of bubbles rising in water. In contrast to previous studies which only focused on one fluid, our system considers both the liquid and the gas simultaneously. In addition to the flowing motion, the interactions between liquid and gas cause buoyancy, surface
Can high-frequency sound affect gas-bubble dynamics? A study in the intact prawn Palaemon elegans
Yehuda Arieli; Ran Arieli; Avi Shupak
Underwater sound beacons (pingers) are employed in professional and scientific diving for location and navigation. Previous studies have demonstrated that exposure to acoustic fields may lead to the emergence of bubbles and cavities in tissues by rectified diffusion. However, this issue was studied mainly in vitro in various gels and isolated tissues. In the present study, we used the intact
Electrowetting-on-dielectrics for manipulation of oil drops and gas bubbles in aqueous-shell compound drops.
Li, Jiang; Wang, Yixuan; Chen, Haosheng; Wan, Jiandi
We present the manipulation of oil, organic and gaseous chemicals by electrowetting-on-dielectric (EWOD) technology using aqueous-shell compound drops. We demonstrate that the transport and coalescence of viscous oil drops, the reaction of bromine with styrene in benzene solution, and the reaction of red blood cells with carbon monoxide bubbles can be accomplished using this method. PMID:25236507
Acoustic emission associated with the bursting of a gas bubble at the free surface of a non-newtonian fluid.
Paris-Sud XI, Universitûˋ de
either volcanoes or foams, where one observes respectively, the bursting of giant bubbles at the free of a volcano vent, or at the surface of a lava lake, are examples whose understanding might be crucial of aqueous foams [3] typically produced by wash- or beauty- products or even by poured beer. The analysis
Controlling the Mobility of the Fluid Interface of Moving Gas Bubbles or Liquid Drops by Using Micellar Solutions of Surfactants
NASA Technical Reports Server (NTRS)
Maldarelli, Charles; Papageorgiou, Demetrios
Microgravity processes must rely on mechanisms other than buoyancy to move bubbles or droplets from one region to another in a continuous liquid phase. One suggested method is thermocapillary migration in which a temperature gradient is applied to the continuous phase. A significant and as yet unresolved impediment to the use of thermocapillary migration to direct bubble or drop motion is that these migrations can be significantly retarded by the adsorption onto the fluid particle surface of surface active impurities unavoidably present in the continuous or (if the particle is a liquid) droplet phases. The focus of our research was to develop a theory for remobilizing fluid particle interfaces retarded by a surfactant impurity in an effort to make more viable the use of thermocapillary migrations for the management of bubbles and drops in microgravity. We postulated that a surfactant at high bulk concentration which kinetically exchanges rapidly with the surface can restore interface mobility. The scaling arguments along with a discussion of the previous literature is reviewed in the context of the scaling framework. The specific objectives of the research were twofold. The first was to prove the remobilization theory by studying a model problem. As the mechanism for remobilization is independent of the force which drives the particle, the fluid particle shape and the presence of fluid inertia, we chose the simplest model consisting of a spherical bubble rising steadily by buoyancy in creeping flow. We solved the hydrodynamic and surfactant transport equations for rapid kinetic exchange to demonstrate that as the concentration increases, the Marangoni retardation at first increases (the low k behavior) and then decreases (the high k behavior). The second objective was to develop a method to determine the kinetic rate constants of a surfactant molecule, since this information is necessary to select surfactants which will exchange rapidly enough relative to the convective rate in the thermocapillary process of interest. To measure the kinetic rate, we measure the dynamic tension change accompanying adsorption onto an initially clean interface, or the re-equilibration in tension when an equilibrium interface is compressed. The dynamic tension measurements are made by a pendant bubble method, in which surfactant adsorbs onto a pendant bubble, and the tension is measured by analyzing the shape change in the bubble. We conclude this report by detailing the publications, presentations and doctoral thesis completed under the auspices of this grant.
Experimental evidence for seismically initiated gas bubble nucleation and growth in groundwater as a mechanism for coseismic borehole water level rise and remotely triggered seismicity
NASA Astrophysics Data System (ADS)
Crews, Jackson B.; Cooper, Clay A.
Changes in borehole water levels and remotely triggered seismicity occur in response to near and distant earthquakes at locations around the globe, but the mechanisms for these phenomena are not well understood. Experiments were conducted to show that seismically initiated gas bubble growth in groundwater can trigger a sustained increase in pore fluid pressure consistent in magnitude with observed coseismic borehole water level rise, constituting a physically plausible mechanism for remote triggering of secondary earthquakes through the reduction of effective stress in critically loaded geologic faults. A portion of the CO2 degassing from the Earth's crust dissolves in groundwater where seismic Rayleigh and P waves cause dilational strain, which can reduce pore fluid pressure to or below the bubble pressure, triggering CO2 gas bubble growth in the saturated zone, indicated by a spontaneous buildup of pore fluid pressure. Excess pore fluid pressure was measured in response to the application of 0.1-1.0 MPa, 0.01-0.30 Hz confining stress oscillations to a Berea sandstone core flooded with initially subsaturated aqueous CO2, under conditions representative of a confined aquifer. Confining stress oscillations equivalent to the dynamic stress of the 28 June 1992 Mw 7.3 Landers, California, earthquake Rayleigh wave as it traveled through the Long Valley caldera, and Parkfield, California, increased the pore fluid pressure in the Berea core by an average of 36 Ý 15 cm and 23 Ý 15 cm of equivalent freshwater head, respectively, in agreement with 41.8 cm and 34 cm rises recorded in wells at those locations.
NASA Astrophysics Data System (ADS)
Lohse, Detlef; Prosperetti, Andrea
In this short overview we report on our ongoing work on the dynamics of bubbles in various flows. Three different situations are explored: the competition between acoustic and hydrodynamics forces in a vertical pipe (Rensen J, Bosman D, Magnaudet J, Ohl C D, Prosperetti A, T—gel R, Versluis M and Lohse D 2001 Phys. Rev. Lett. 86 4819), a rising bubble on which shape oscillations have been induced (de Vries J, Luther S and Lohse D 2002 Eur. J. Phys. B 29 503), and a bubble in a rotating horizontal cylinder. Whereas for the first two situations the standard bubble force models (Magnaudet J and Eames I 2000 Annu. Rev. Fluid Mech. 32 659) are consistent with our measurements, modifications for the lift force model seem to be required in the last case.
NSDL National Science Digital Library
WGBH Boston
In this activity, learners mix up a bubbly brew and examine density. Learners explore how they can make different materials fall and rise in water using oil, water, and salt. Learners can experiment using other materials like sugar and sand.
Generator for single bubbles of controllable size
NASA Astrophysics Data System (ADS)
Ohl, C. D.
A new type of apparatus for the production of single bubbles of adjustable size is presented. A single bubble is generated by injecting a short burst of gas into a liquid channel flow. The radius of the bubble can be varied continuously from 300 ?m up to a 3 mm by adjusting the timing of a valve injecting the gas. The device works also in liquids with variable pressure and can be microcomputer controlled.
Model of single bubble sonoluminescence
An Yu; Ying, C.F. [Department of Physics, Tsinghua University, Beijing 100084 (China); Institute of Acoustics, Chinese Academy of Science, Beijing 100080 (China)
The temperature within and the sonoluminescence characteristics of a stable inert-gas single bubble grown in water under some given conditions are computed by using a model that is as sufficiently complete as we can manage, except that possible chemical reactions within the bubble are neglected. We work with several different versions of the equation describing the motion of the bubble wall, which are usually considered to give merely slight differences; or vary a parameter in the formula calculating the net increment of the water condensed at the bubble wall. It is found that the final outcomes of the temperature and the sonoluminescence can be significantly different in some cases. This illustration points to the importance of differentiating among the various seemingly similar equations and of adopting the correct value of the parameter used in the computation model of a single bubble.
Bubble fusion: Preliminary estimates
Krakowski, R.A.
The collapse of a gas-filled bubble in disequilibrium (i.e., internal pressure {much_lt} external pressure) can occur with a significant focusing of energy onto the entrapped gas in the form of pressure-volume work and/or acoustical shocks; the resulting heating can be sufficient to cause ionization and the emission of atomic radiations. The suggestion that extreme conditions necessary for thermonuclear fusion to occur may be possible has been examined parametrically in terms of the ratio of initial bubble pressure relative to that required for equilibrium. In this sense, the disequilibrium bubble is viewed as a three-dimensional ``sling shot`` that is ``loaded`` to an extent allowed by the maximum level of disequilibrium that can stably be achieved. Values of this disequilibrium ratio in the range 10{sup {minus}5}--10{sup {minus}6} are predicted by an idealized bubble-dynamics model as necessary to achieve conditions where nuclear fusion of deuterium-tritium might be observed. Harmonic and aharmonic pressurizations/decompressions are examined as means to achieve the required levels of disequilibrium required to create fusion conditions. A number of phenomena not included in the analysis reported herein could enhance or reduce the small levels of nuclear fusions predicted.
What Can Be Learned from X-Ray Spectroscopy Concerning Hot Gas in the Local Bubble and Charge Exchange Processes?
NASA Technical Reports Server (NTRS)
Snowden, S. L.
Both solar wind charge exchange emission and diffuse thermal emission from the Local Bubble are strongly dominated in the soft X-ray band by lines from highly ionized elements. While both processes share many of the same lines, the spectra should differ significantly due to the different production mechanisms, abundances, and ionization states. Despite their distinct spectral signatures, current and past observatories have lacked the spectral resolution to adequately distinguish between the two sources. High-resolution X-ray spectroscopy instrumentation proposed for future missions has the potential to answer fundamental questions such as whether there is any hot plasma in the Local Hot Bubble, and if so, what are the abundances of the emitting plasma and whether the plasma is in equilibrium. Such instrumentation will provide dynamic information about the solar wind including data on ion species which are currently difficult to track. It will also make possible remote sensing of the solar wind.
Modelling isothermal bubbly-cap flows using two-group averaged bubble number density approach
NASA Astrophysics Data System (ADS)
Cheung, S. C. P.; Yeoh, G. H.; Tu, J. Y.
Gas-liquid flows with wide range of bubble sizes are commonly encountered in many nuclear gas-liquid flow systems. In tracking the changes of gas volume fraction and bubble size distribution under complex flow conditions, numerical studies have been performed to predict the temporal and spatial evolution of two-phase geometrical structure caused by the effects of bubble interactions in gas-liquid flows. Within literatures, the development of most coalescence and break-up mechanisms were primarily focused on the interaction of spherical bubbles. Nevertheless, cap bubbles which are precursors to the formation of slug units in the slug flow regime with increasing volume fraction become ever more prevalent at high gas velocity conditions. It has been shown through many experiments that interaction behaviors between non-spherical bubbles in a liquid flow are remarkably different when compared to those of spherical bubbles. Based on the computational fluid dynamics (CFD) framework, a three-fluid model was solved, one set of conservation equations for the liquid phase while two sets of conservation equations for the gas phase with one being Group 1 spherical bubbles and the other depicting Group 2 cap bubbles. In this initial assessment, the bubble mechanistic models proposed by Hibiki and Ishii [1] have been adopted to describe the intra-group and inter-group interactions. The numerical predictions were evaluated against the experiment data of the TOPFLOW facility for vertical, upwards, airwater flows in a large pipe diameter [2].
Flow structure and phase distributions in a slurry bubble column
Warsito M. Ohkawa; A. Maezawa; S. Uchida
In this paper, the axial and radial distributions of the gas and solid concentrations in a slurry bubble column are measured by an ultrasonic penetration technique, which provides a method capable of monitoring simultaneously the concentrations of the gas bubbles and the solid particles in the system. The macroscopic flow structure of the slurry bubble column is analyzed based on
Seismically Initiated Carbon Dioxide Gas Bubble Growth in Groundwater: A Mechanism for Co-seismic Borehole Water Level Rise and Remotely Triggered Secondary Seismicity
NASA Astrophysics Data System (ADS)
Crews, Jackson B.
Visualization experiments, core-scale laboratory experiments, and numerical simulations were conducted to examine the transient effect of dilational seismic wave propagation on pore fluid pressure in aquifers hosting groundwater that is near saturation with respect to dissolved carbon dioxide (CO2) gas. Groundwater can become charged with dissolved CO2 through contact with gas-phase CO2 in the Earth's crust derived from magma degasing, metamorphism, and biogenic processes. The propagation of dilational seismic waves (e.g., Rayleigh and p-waves) causes oscillation of the mean normal confining stress and pore fluid pressure. When the amplitude of the pore fluid pressure oscillation is large enough to drive the pore fluid pressure below the bubble pressure, an aqueous-to-gas-phase transition can occur in the pore space, which causes a buildup of pore fluid pressure and reduces the inter-granular effective stress under confined conditions. In visualization experiments conducted in a Hele-Shaw cell representing a smooth-walled, vertically oriented fracture, millisecond-scale pressure perturbations triggered bubble nucleation and growth lasting tens of seconds, with resulting pore fluid overpressure proportional to the magnitude of the pressure perturbation. In a Berea sandstone core flooded with initially under-saturated aqueous CO2 under conditions representative of a confined aquifer, rapid reductions in confining stress triggered transient pore pressure rise up to 0.7 MPa (100 psi) overpressure on a timescale of ~10 hours. The rate of pore pressure buildup in the first 100 seconds was proportional to the saturation with respect to dissolved CO 2 at the pore pressure minimum. Sinusoidal confining stress oscillations on a Berea sandstone core produced excess pore fluid pressure after the oscillations were terminated. Confining stress oscillations in the 0.1-0.4 MPa (15-60 psi) amplitude range and 0.05-0.30 Hz frequency band increased the pore fluid pressure by 13-60 cm of freshwater. Co-seismic borehole water level increases of the same magnitude were observed in Parkfield, California, and Long Valley caldera, California, in response to the propagation of a Rayleigh wave in the same amplitude and frequency range produced by the June 28, 1992 MW 7.3 Landers, California, earthquake. Co-seismic borehole water level rise is well documented in the literature, but the mechanism is not well understood, and the results of core-scale experiments indicate that seismically initiated CO2 gas bubble nucleation and growth in groundwater is a reasonable mechanism. Remotely triggered secondary seismicity is also well documented, and the reduction of effective stress due to CO2 bubble nucleation and growth in critically loaded faults may potentially explain how, for example, the June 28, 1992 MW 7.3 Landers, California, earthquake triggered seismicity as far away as Yellowstone, Wyoming, 1250 km from the hypocenter. A numerical simulation was conducted using Euler's method and a first-order kinetic model to compute the pore fluid pressure response to confining stress excursions on a Berea sandstone core flooded with initially under-saturated aqueous CO2. The model was calibrated on the pore pressure response to a rapid drop and later recovery of the confining stress. The model predicted decreasing overpressure as the confining stress oscillation frequency increased from 0.05 Hz to 0.30 Hz, in contradiction with the experimental results and field observations, which exhibit larger excess pore fluid pressure in response to higher frequency oscillations. The limitations of the numerical model point to the important influence of non-ideal behavior arising from a discontinuous gas phase and complex dynamics at the gas-liquid interface.
Achieving Higher Accuracy in the Gamma-Ray Spectrocopic Assay of Holdup
Russo, P.A.; Wenz, T.R.; Smith, S.E.; Harris, J.F.
Gamma-ray spectroscopy is an important technique for the measurement of quantities of nuclear material holdup in processing equipment. Because the equipment in large facilities dedicated to uranium isotopic enrichment, uranium/plutonium scrap recovery or various stages of fuel fabrication is extensive, the total holdup may be large by its distribution alone, even if deposit thicknesses are small. Good accountability practices require unbiased measurements with uncertainties that are as small as possible. This paper describes new procedures for use with traditional holdup analysis methods based on gamma-ray spectroscopy. The procedures address the two sources of bias inherent in traditional gamma-ray measurements of holdup. Holdup measurements are performed with collimated, shielded gamma-ray detectors. The measurement distance is chosen to simplify the deposit geometry to that of a point, line or area. The quantitative holdup result is based on the net count rate of a representative gamma ray. This rate is corrected for contributions from room background and for attenuation by the process equipment. Traditional holdup measurements assume that the width of the point or line deposit is very small compared to the measurement distance, and that the self-attenuation effects can be neglected. Because each point or line deposit has a finite width and because self-attenuation affects all measurements, bias is incurred in both assumptions. In both cases the bias is negative, explaining the systematically low results of gamma-ray holdup measurements. The new procedures correct for bias that arises from both the finite-source effects and the gamma-ray self-attenuation. The procedures used to correct for both of these effects apply to the generalized geometries. One common empirical parameter is used for both corrections. It self-consistently limits the total error incurred (from uncertain knowledge of this parameter) in the combined correction process, so that it is compelling to use these procedures. The algorithms and the procedures are simple, general, and easily automated for use plant-wide. This paper shows the derivation of the new, generalized correction algorithms for finite-source and self-attenuation effects. It also presents an analysis of the sensitivity of the holdup result to the uncertainty in the empirical parameter when one or both corrections are made. The paper uses specific examples of the magnitudes of finite-source and self-attenuation corrections to measurements that were made in the field. It discusses the automated implementation of the correction procedure.
Oscillation of Droplets and Bubbles
N. Ashgriz; M. Movassat
\\u000a A liquid droplet may go through shape oscillation if it is forced out of its equilibrium spherical shape, while gas bubbles\\u000a undergo both shape and volume oscillations because they are compressible. This can happen when droplets and bubbles are exposed\\u000a to an external flow or an external force. Liquid droplet oscillation is observed during the atomization process when a liquid
Microwave, optical and IR combined studies of the sea surface perturbations caused by underwater gas bubble plume
M. G. Bulatov; Yu. A. Kravtsov; M. D. Raev; I. A. Repina; E. I. Skvortsov
In connection with extensive world-wide development of transporting gas networks the problem of the gas leakage detection on the underwater gas pipes becomes rather actual. The present paper is devoted to the solution of the problem of underwater gas plume detection by microwave remote sensing methods.
Single-bubble sonochemiluminescence in aqueous luminol solutions.
Hatanaka, Shin-Ichi; Mitome, Hideto; Yasui, Kyuichi; Hayashi, Shigeo
Sonochemiluminescence (SCL) of luminol due to a single bubble is studied through spectral measurement. No SCL was observed from a stable single bubble that emitted high-intensity sonoluminescence (SL). In contrast, SCL was observed under conditions of an unstable dancing bubble, where a bubble grows and ejects tiny bubbles, making it "dance" by counteraction. Furthermore, SCL was observed from dancing bubbles even when SL was not observed, depending on the dissolved gas content. The instability of bubble collapse is the key parameter governing SCL. PMID:12197706
Holdup Measurement System II (HMSII): Version 2.1. User`s guide and software documentation
Smith, S.E.
The Holdup Measurement System II (HMSII) software is a database management package for doing Holdup Measurements. It is based on the generalized geometry holdup (GGH) methodology taught in the US Department of Energy Safeguards Technology Training Program, ``Nondestructive Assay of Special Nuclear Materials Holdup.`` This program was developed and taught by Los Alamos National Laboratory (LANL). The HMSII was developed as a joint effort between LANL and the Oak Ridge Y-12 Plant, managed for the US Department of Energy by Lockheed Martin Energy Systems, Inc. The system is designed specifically for use with three types of Multichannel Analyzer (MCA): a Davidson Portable MultiChannel Analyzer (MCA); a EG&G Ortec MicroNOMAD ({mu}NOMAD); or a new Miniature Modular MultiChannel Analyzer (M{sup 3}CA) under development at LANL. It is also designed assuming a 512 channel spectrum from a low resolution (e.g., NaI) detector measuring Uranium or Plutonium. Another important hardware component of the system is a portable bar code reader (also called a DataLogger or Trakker), by Intermec Corporation. The 944X series and the JANUS 2OXX series readers are compatible models with the HMSII. The JANUS series is a bar code reader which is also a 386 compatible palmtop PC with MS-DOS 5.0 built-in. Both series readers are programmable and control all the aspects of field holdup data collection from the MCAs.
First measurements of gas output from bubbling pools in a mud volcano at the periphery of Mt Etna (Italy): methodologies and implications for monitoring purposes
NASA Astrophysics Data System (ADS)
Federico, Cinzia; Giudice, Gaetano; Liuzzo, Marco; Pedone, Maria; Cosenza, Paolo; Riccobono, Giuseppe
Gases and brines emitted in the southern sector of Mt Etna from mofettes, mud pools and mud volcanoes come from an hydrothermal reservoir hosted within the clayey formations of the sedimentary basement (Chiodini et al., 1996). The gas emitted consists mainly of CO2, with CH4, N2 and He as minor species. CO2 and He stable isotopes indicate a clear magmatic origin for these gases, and their compositional changes during either eruptive or rest periods closely parallel that of crater fumaroles (Paonita et al., 2012). Altough these manifestations are the most significant CO2 emitters outside the crater area, their mass output has never been measured. We present the first measurements of gas flux from several bubbling mud pools in a mud volcano located in the village of Patern· (Lon 14.89¯ Lat 37.57¯), in the southern flank of the volcano. We performed gas measurements using a home-made apparatus, able to capture all the bubbles over an area of 0.4 m2. Over an area of about 7000 m2, we measured the flow rate of every single bubbling pool, providing that it had a minimum flux rate of 0.5 l/min. The maximum measured flow rate for a single pool was 15 l/min. A preliminary estimate of the total CO2 output over the whole mud volcano is in the order of few t/d. At the same time, we measured the chemical composition of emitted gases in various pools, characterised by different gas flow rates, to calculate the output of CO2 and verify the effect of eventual chemical fractionation processes upon gas chemistry. During the same campaign of direct measurements, we also used a commercial infrared laser unit (GasFinder 2.0 from Boreal Laser Ltd) for measurement of volcanic CO2 path-integrated concentrations along cross-sections of the atmospheric plumes in the area. The GasFinder was set as to measure CO2 concentrations at 1 Hz rate. During the field campaigns, the position of the GasFinder unit was sequentially moved so as to scan the plumes from different viewing directions and angles. The positions of both laser source and retro-reflectors were chosen so to have the target CO2 plume in between retro-reflectors and the GasFinder, and to realize the complete coverage of the degassing area. We therefore explored the possibility to combine the available path-integrated CO2 concentration data to derive a two-dimensional mapping of CO2 over the mud volcano. The periodic survey of total CO2 output in a subset of vigorously degassing pools, paralleled to the chemical and isotopic measurements routinely performed in selected pools, would offer a robust monitoring tool in a peripheral sector of the volcano. Chiodini G., D'Alessandro W. and Parello F. (1996) Geochemistry of gases and water discharged by the mud volcanoes at Patern·, Mt. Etna (Italy). Bull. Volcanol. 58, 51-58. Paonita A., Caracausi A., Iacono-Marziano G., Martelli M., Rizzo A. (2012) Geochemical evidence for mixing between fluids exsolved at different depths in the magmatic system of Mt Etna (Italy). Geochim. Cosmochim. Acta 84 (2012) 380-394.
Stable tridimensional bubble clusters in multi-bubble sonoluminescence (MBSL).
Rossellµ, J M; Dellavale, D; Bonetto, F J
In the present work, stable clusters made of multiple sonoluminescent bubbles are experimentally and theoretically studied. Argon bubbles were acoustically generated and trapped using bi-frequency driving within a cylindrical chamber filled with a sulfuric acid aqueous solution (SA85w/w). The intensity of the acoustic pressure field was strong enough to sustain, during several minutes, a large number of positionally and spatially fixed (without pseudo-orbits) sonoluminescent bubbles over an ellipsoidally-shaped tridimensional array. The dimensions of the ellipsoids were studied as a function of the amplitude of the applied low-frequency acoustic pressure (PAc(LF)) and the static pressure in the fluid (P0). In order to explain the size and shape of the bubble clusters, we performed a series of numerical simulations of the hydrodynamic forces acting over the bubbles. In both cases the observed experimental behavior was in excellent agreement with the numerical results. The simulations revealed that the positionally stable region, mainly determined by the null primary Bjerknes force (F?Bj), is defined as the outer perimeter of an axisymmetric ellipsoidal cluster centered in the acoustic field antinode. The role of the high-frequency component of the pressure field and the influence of the secondary Bjerknes force are discussed. We also investigate the effect of a change in the concentration of dissolved gas on the positional and spatial instabilities through the cluster dimensions. The experimental and numerical results presented in this paper are potentially useful for further understanding and modeling numerous current research topics regarding multi-bubble phenomena, e.g. forces acting on the bubbles in multi-frequency acoustic fields, transient acoustic cavitation, bubble interactions, structure formation processes, atomic and molecular emissions of equal bubbles and nonlinear or unsteady acoustic pressure fields in bubbly media. PMID:24974006
Comparison of electrical capacitance tomography & gamma densitometer measurement in viscous oil-gas flows
NASA Astrophysics Data System (ADS)
Archibong Eso, A.; Zhao, Yabin; Yeung, Hoi
Multiphase flow is a common occurrence in industries such as nuclear, process, oil & gas, food and chemical. A prior knowledge of its features and characteristics is essential in the design, control and management of such processes due to its complex nature. Electrical Capacitance Tomography (ECT) and Gamma Densitometer (Gamma) are two promising approaches for multiphase visualization and characterization in process industries. In two phase oil & gas flow, ECT and Gamma are used in multiphase flow monitoring techniques due to their inherent simplicity, robustness, and an ability to withstand wide range of operational temperatures and pressures. High viscous oil (viscosity > 100 cP) is of interest because of its huge reserves, technological advances in its production and unlike conventional oil (oil viscosity < 100 cP) and gas flows where ECT and Gamma have been previously used, high viscous oil and gas flows comes with certain associated concerns which include; increased entrainment of gas bubbles dispersed in oil, shorter and more frequent slugs as well as oil film coatings on the walls of flowing conduits. This study aims to determine the suitability of both devices in the visualization and characterization of high-viscous oil and gas flow. Static tests are performed with both devices and liquid holdup measurements are obtained. Dynamic experiments were also conducted in a 1 & 3 inch facility at Cranfield University with a range of nominal viscosities (1000, 3000 & 7500 cP). Plug, slug and wavy annular flow patterns were identified by means of Probability Mass Function and time series analysis of the data acquired from Gamma and ECT devices with high speed camera used to validate the results. Measured Liquid holdups for both devices were also compared.
Comparison of electrical capacitance tomography and gamma densitometer measurement in viscous oil-gas flows
Archibong Eso, A.; Zhao, Yabin; Yeung, Hoi [Department of Offshore Process and Energy Systems Engineering, Cranfield University, Cranfield (United Kingdom)
Multiphase flow is a common occurrence in industries such as nuclear, process, oil and gas, food and chemical. A prior knowledge of its features and characteristics is essential in the design, control and management of such processes due to its complex nature. Electrical Capacitance Tomography (ECT) and Gamma Densitometer (Gamma) are two promising approaches for multiphase visualization and characterization in process industries. In two phase oil and gas flow, ECT and Gamma are used in multiphase flow monitoring techniques due to their inherent simplicity, robustness, and an ability to withstand wide range of operational temperatures and pressures. High viscous oil (viscosity > 100 cP) is of interest because of its huge reserves, technological advances in its production and unlike conventional oil (oil viscosity < 100 cP) and gas flows where ECT and Gamma have been previously used, high viscous oil and gas flows comes with certain associated concerns which include; increased entrainment of gas bubbles dispersed in oil, shorter and more frequent slugs as well as oil film coatings on the walls of flowing conduits. This study aims to determine the suitability of both devices in the visualization and characterization of high-viscous oil and gas flow. Static tests are performed with both devices and liquid holdup measurements are obtained. Dynamic experiments were also conducted in a 1 and 3 inch facility at Cranfield University with a range of nominal viscosities (1000, 3000 and 7500 cP). Plug, slug and wavy annular flow patterns were identified by means of Probability Mass Function and time series analysis of the data acquired from Gamma and ECT devices with high speed camera used to validate the results. Measured Liquid holdups for both devices were also compared.
A. T. Hare
I HAVE on several occasions noticed the beautiful bubbles described by Mr. Wright and Sir William Crookes (pp. 8 and 37). On each occasion I was purifying mercury in the following way. I half filled a rather large Woulffe's bottle with mercury and poured on to it weak nitric acid. Then, in order to keep, the whole in a state
235U Holdup Measurements in Three 321-M Exhaust HEPA Banks
Dewberry, R
The Analytical Development Section of Savannah River National Laboratory (SRNL) was requested by the Facilities Disposition Division to determine the holdup of enriched uranium in the 321-M facility as part of an overall deactivation project of the facility. The 321-M facility was used to fabricate enriched uranium fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the production reactors. The results of the holdup assays are essential for determining compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to meet criticality safety controls. This report covers holdup measurements of uranium residue in three HEPA filter exhaust banks of the 321-M facility. Each of the exhaust banks has dimensions near 7' x 14' x 4' and represents a complex holdup problem. A portable HPGe detector and EG&G Dart system that contains the high voltage power supply and signal processing electronics were used to determine highly enriched uranium (HEU) holdup. A personal computer with Gamma-Vision software was used to control the Dart MCA and to provide space to store and manipulate multiple 4096-channel {gamma}-ray spectra. Some acquisitions were performed with the portable detector configured to a Canberra Inspector using NDA2000 acquisition and analysis software. Our results for each component uses a mixture of redundant point source and area source acquisitions that yielded HEU contents in the range of 2-10 grams. This report discusses the methodology, non-destructive assay (NDA) measurements, assumptions, and results of the uranium holdup in these items. This report includes use of transmission-corrected assay as well as correction for contributions from secondary area sources.
Investigation of the effects of radiolytic-gas bubbles on the long-term operation of solution reactors for medical-isotope production
NASA Astrophysics Data System (ADS)
Souto Mantecon, Francisco Javier
One of the most common and important medical radioisotopes is 99Mo, which is currently produced using the target irradiation technology in heterogeneous nuclear reactors. The medical isotope 99Mo can also be produced from uranium fission using aqueous homogeneous solution reactors. In solution reactors, 99Mo is generated directly in the fuel solution, resulting in potential advantages when compared with the target irradiation process in heterogeneous reactors, such as lower reactor power, less waste heat, and reduction by a factor of about 100 in the generation of spent fuel. The commercial production of medical isotopes in solution reactors requires steady-state operation at about 200 kW. At this power regime, the formation of radiolytic-gas bubbles creates a void volume in the fuel solution that introduces a negative coefficient of reactivity, resulting in power reduction and instabilities that may impede reactor operation for medical-isotope production. A model has been developed considering that reactivity effects are due to the increase in the fuel-solution temperature and the formation of radiolytic-gas bubbles. The model has been validated against experimental results from the Los Alamos National Laboratory uranyl fluoride Solution High-Energy Burst Assembly (SHEBA), and the SILENE uranyl nitrate solution reactor, commissioned at the Commissariat a l'Energie Atomique, in Valduc, France. The model shows the feasibility of solution reactors for the commercial production of medical isotopes and reveals some of the important parameters to consider in their design, including the fuel-solution type, 235U enrichment, uranium concentration, reactor vessel geometry, and neutron reflectors surrounding the reactor vessel. The work presented herein indicates that steady-state operation at 200 kW can be achieved with a solution reactor consisting of 120 L of uranyl nitrate solution enriched up to 20% with 235U and a uranium concentration of 145 kg/m3 in a graphite-reflected cylindrical geometry.
Buoyancy Driven Shear Flows of Bubble Suspensions
NASA Astrophysics Data System (ADS)
Hill, R. J.; Zenit, R.; Chellppannair, T.; Koch, D. L.; Spelt, P. D. M.; Sangani, A.
In this work the gas volume fraction and the root-mean-squared fluid velocity are measured in buoyancy driven shear flows of bubble suspensions in a tall, inclined, rectangular channel. The experiments are performed under conditions where We << 1 and Re >> 1 , so that the bubbles are relatively undeformed and the flow is inviscid and approximately irrotational. Nitrogen is introduced through an array of capillaries at the base of a .2x.02x2 m channel filled with an aqueous electrolyte solution (0.06 molL-1 MgSO_4). The rising bubbles generate a unidirectional shear flow, where the denser suspension at the lower surface of the channel falls, while the less dense suspension at the upper surface rises. Hot-film anemometry is used to measure the resulting gas volume fraction and fluid velocity profiles. The bubble collision rate with the sensor is related to the gas volume fraction and the mean and variance of the bubble velocity using an experimentally measured collision surface area for the sensor. Bubble collisions with the sensor are identified by the characteristic slope of the hot-film anemometer signal when bubbles collide with the sensor. It is observed that the steady shear flow develops a bubble phase pressure gradient across the channel gap as the bubbles interchange momentum through direct collisions. The discrete phase presssure gradient balances the buoyancy force driving bubbles toward the upper surface resulting in a steady void fraction profile across the gap width. The strength of the shear flow is controlled by the extent of bubble segregation and by the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion (Kang et al. 1997; Spelt and Sangani, 1998), for a range of gas volume fractions and channel inclination angles.
Simulations of Bubble Motion in an Oscillating Liquid
NASA Astrophysics Data System (ADS)
Kraynik, A. M.; Romero, L. A.; Torczynski, J. R.
Finite-element simulations are used to investigate the motion of a gas bubble in a liquid undergoing vertical vibration. The effect of bubble compressibility is studied by comparing "compressible" bubbles that obey the ideal gas law with "incompressible" bubbles that are taken to have constant volume. Compressible bubbles exhibit a net downward motion away from the free surface that does not exist for incompressible bubbles. Net (rectified) velocities are extracted from the simulations and compared with theoretical predictions. The dependence of the rectified velocity on ambient gas pressure, bubble diameter, and bubble depth are in agreement with the theory. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
A Laboratory Experiment To Measure Henry's Law Constants of Volatile Organic Compounds with a Bubble Column and a Gas
Lee, Shan-Hu
and these VOCs can directly participate in the production of ozone and secondary aerosol particles and in turn, steady-state equilibrium of the solute is reached between the gas and aqueous phases in an enclosed (in the headspace) and the aqueous phases, the decay of gas phase concentrations of the solute
Computed optical emissions from a sonoluminescing bubble
William C. Moss; David A. Young; Judith A. Harte; Joanne L. Levatin; Balazs F. Rozsnyai; George B. Zimmerman; I. Harold Zimmerman
A sonoluminescing bubble has been modeled as a thermally conducting, partially ionized plasma. The model is more complete than previous models, due to the inclusion of both plasma and normal molecular thermal conduction, vapor pressure, surface tension, the mixing of gas and water vapor in the bubble, and opacities. The model accounts for most of the observed experimental trends, including
Injunctions, Hold-Up, and Patent Royalties Carl Shapiro, University of California at Berkeley
Sadoulet, Elisabeth
Injunctions, Hold-Up, and Patent Royalties Carl Shapiro, University of California at Berkeley Send royalty negotiations between a patent holder and a downstream firm whose product is more valuable if it includes a feature cov- ered by the patent. The downstream firm must make specific investments to de- velop
Bougie-related airway trauma: dangers of the hold-up sign.
Marson, B A; Anderson, E; Wilkes, A R; Hodzovic, I
The bougie is a popular tool in difficult intubations. The hold-up sign is used to confirm tracheal placement of a bougie. This study aimed to establish the potential for airway trauma when using this sign with an Eschmann re-usable bougie or a Frova single-use bougie. Airways were simulated using a manikin (hold-up force) and porcine lung model (airway perforation force). Mean (SD) hold-up force (for airway lengths over the range 25-45 cm) of 1.0 (0.4) and 5.2 (1.1) N were recorded with the Eschmann and Frova bougies, respectively (p < 0.001). The mean (SD) force required to produce airway perforation was 0.9 (0.2) N with the Eschmann bougie and 1.1 (0.3) N with the Frova bougie (p = 0.11). It is possible to apply a force at least five times greater than the force required to produce significant trauma with a Frova single-use bougie. We recommend that the hold-up sign should no longer be used with single-use bougies. Clinicians should be cautious when eliciting this sign using the Eschmann re-usable bougie. PMID:24548354
Simulation of bubbly flows: Comparison between direct quadrature method of moments (DQMOM) and method of classes (CM)
B. Selma; R. Bannari; P. Proulx
In typical bubbly flow applications, bubbles can break or coalesce due to bubblebubble and bubblefluid interactions in presence of turbulence. Under this assumption, a fixed bubble size model might not be suitable for predicting correct multiphase flow behaviour in the gasliquid system. For example, breakage and coalescence events produce very different bubble size distribution and then affects the interfacial interactions
Mechanisms of stability of armored bubbles: FY 1995 progress report
W. R. Rossen; S. K. Das
Experimental and theoretical studies of stabilization of liquid films between bubbles were undertaken as part of an effort to model gas release in waste tanks at the Hanford nuclear reservation. Synthetic Hanford waste created here showed solids accumulation at bubble surfaces and some stabilization of bubbles in a froth upon sparging with nitrogen. Dilational interfacial rheological measurements indicate increasing hydrophobicity
Bubble-Free Containers For Liquids In Microgravity
NASA Technical Reports Server (NTRS)
Kornfeld, Dale M.; Antar, Basil L.
Reports discuss entrainment of gas bubbles during handling of liquids in microgravity, and one report proposes containers filled with liquids in microgravity without entraining bubbles. Bubbles are troublesome in low-gravity experiments - particularly in biological experiments. Wire-mesh cage retains liquid contents without solid wall, because in microgravity, surface tension of liquid exerts sufficient confining force.
Characterization of capacitance sensor for the measurement of water droplet in gas
NASA Astrophysics Data System (ADS)
Guo, Liye; Yang, Yunjie; Lei, Lei; Peng, Lihui
The measurement of water droplet in gas may play an important role in air-condition, gas delivery under precise instrument environment or other applications. To fulfill the requirement of the detection of water droplet hold-up in gas-liquid two-phase flow, the characterization of capacitance sensor is studied. Two classicalcategories of capacitancesensors, which are capacitance sensors with concave electrode and helical electrode, areinvestigated comparatively by simulation and experiments. The simulation results show that concave capacitance appears better performances in the measurement of water droplet in gas. Droplet near the helical electrode (near the pipe wall) may cause considerably higher capacitance fluctuation than that locates centrally, which would result in high measure error or uncertainty in real applications. On the contract, the concave electrode has less capacitance fluctuation. The spanning angle of concave electrodes is the main factor that influences the sensor sensitivity distribution. To achieve the best angle of concave electrodes, the characterization of concave capacitance sensor is investigated theoretically. The sensitivity distribution is obtained by COMSOL Multiphysics and quantitativelyanalyzed. The sensitivity distribution of concave sensor has the shape of a saddle, high sensitivity in the edge of electrodes and negative sensitivity between the edges of different electrodes. The capacitancesare calculated while water droplet in different positions under different concave electrode angles. By interpolation calculation, the optimal concave capacitance sensor with homogeneous sensitivity distribution is obtained aselectrode spanning angle of 135¯ and verified by experiments. The test samplesmonitoring water droplet including small rubble bubble with water inside, small wet paper ball, etc., havebeen used to conduct the static experiment. The relationship between the capacitance variation and water droplet hold-up is obtained. The preliminary results show that the designed sensor is able to measure water droplet of 1ml.
Bubbles and foams in microfluidics.
Huerre, Axel; Miralles, Vincent; Jullien, Marie-Caroline
Microfluidics offers great tools to produce highly-controlled dispersions of gas into liquid, from isolated bubbles to organized microfoams. Potential technological applications are manifold, from novel materials to scaffolds for tissue engineering or enhanced oil recovery. More fundamentally, microfluidics makes it possible to investigate the physics of complex systems such as foams at scales where the capillary forces become dominant, in model experiments involving few well-controlled parameters. In this context, this review does not have the ambition to detail in a comprehensive manner all the techniques and applications involving bubbles and foams in microfluidics. Rather, it focuses on particular consequences of working at the microscale, under confinement, and hopes to provide insight into the physics of such systems. The first part of this work focuses on bubbles, and more precisely on (i) bubble generation, where the confinement can suppress capillary instabilities while inertial effects may play a role, and (ii) bubble dynamics, paying special attention to the lubrication film between bubble and wall and the influence of confinement. The second part addresses the formation and dynamics of microfoams, emphasizing structural differences from macroscopic foams and the influence of the confinement. PMID:24913678
Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble?s dynamics
M. Mahdi; R. Ebrahimi; M. Shams
A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with
Discrete Bubble Modeling for Cavitation Bubbles
NASA Astrophysics Data System (ADS)
Choi, Jin-Keun; Chahine, Georges; Hsiao, Chao-Tsung
Dynaflow, Inc. has conducted extensive studies on non-spherical bubble dynamics and interactions with solid and free boundaries, vortical flow structures, and other bubbles. From these studies, emerged a simplified Surface Averaged Pressure (SAP) spherical bubble dynamics model and a Lagrangian bubble tracking scheme. In this SAP scheme, the pressure and velocity of the surrounding flow field are averaged on the bubble surface, and then used for the bubble motion and volume dynamics calculations. This model is implemented using the Fluent User Defined Function (UDF) as Discrete Bubble Model (DBM). The Bubble dynamics portion can be solved using an incompressible liquid modified Rayleigh-Plesset equation or a compressible liquid modified Gilmore equation. The Discrete Bubble Model is a very suitable tool for the studies on cavitation inception of foils and turbo machinery, bubble nuclei effects, noise from the bubbles, and can be used in many practical problems in industrial and naval applications associated with flows in pipes, jets, pumps, propellers, ships, and the ocean. Applications to propeller cavitation, wake signatures of waterjet propelled ships, bubble-wake interactions, modeling of cavitating jets, and bubble entrainments around a ship will be presented.
Numerical simulations of non-spherical bubble collapse
A high-order accurate shock- and interface-capturing scheme is used to simulate the collapse of a gas bubble in water. In order to better understand the damage caused by collapsing bubbles, the dynamics of the shock-induced and Rayleigh collapse of a bubble near a planar rigid surface and in a free field are analysed. Collapse times, bubble displacements, interfacial velocities and
Electrolysis Bubbles Make Waterflow Visible
NASA Technical Reports Server (NTRS)
Schultz, Donald F.
Technique for visualization of three-dimensional flow uses tiny tracer bubbles of hydrogen and oxygen made by electrolysis of water. Strobe-light photography used to capture flow patterns, yielding permanent record that is measured to obtain velocities of particles. Used to measure simulated mixing turbulence in proposed gas-turbine combustor and also used in other water-table flow tests.
Analysis of bubble dynamics and local hydrodynamics based on instantaneous heat transfer measurements in a slurry bubble column
H. Li; A. Prakash
A fast response heat transfer probe was designed to measure local instantaneous heat transfer coefficients at various gas velocities and slurry concentrations in a slurry bubble column. The enhancement of heat transfer due to turbulent bubble-wake region has been analyzed to understand bubble-wake dynamics. To quantitatively describe instantaneous heat transfer coefficient due to bubble-wake enhancement, a peak-fitting method was applied
Multiple effects of operating variables on the bubble properties in three-phase slurry bubble columns
Ik Sang Shin; Sung Mo Son; Uk Yeong Kim; Yong Kang; Sang Done Kim; Heon Jung
Flow properties of gas phase reactants such as size, rising velocity and frequency were investigated in simulated three-phase\\u000a slurry bubble column reactors. Effects of gas velocity, reactor pressure, liquid viscosity, solid content in the slurry phase\\u000a and column diameter on the flow properties of a gas reactant were determined. The multiple effects of operating variables\\u000a on the bubble properties were
Buoyancy Driven Shear Flows of Bubble Suspensions
NASA Technical Reports Server (NTRS)
Koch, D. L.; Hill, R. J.; Chellppannair, T.; Zenit, R.; Zenit, R.; Spelt, P. D. M.
In this work the gas volume fraction and the root-mean-squared fluid velocity are measured in buoyancy driven shear flows of bubble suspensions in a tall, inclined, rectangular channel. The experiments are performed under conditions where We << 1a nd Re >> 1, for which comparisons are made with kinetic theory and numerical simulations. Here Re = gamma(a(exp 2)/nu is the Reynolds number and We = rho(gamma(exp 2))a(exp 3)/sigma is the Weber number; gamma is the shear rate, a is the bubble radius, nu is the kinematic viscosity of the liquid, rho is the density of the liquid, and sigma is the surface tension of the gas/liquid interface. Kang et al. calculated the bubble phase pressure and velocity variance of sheared bubble suspensions under conditions where the bubbles are spherical and the liquid phase velocity field can be approximated using potential flow theory, i.e. We= 0 and Re >> 1. Such conditions can be achieved in an experiment using gas bubbles, with a radius of O(0.5mm), in water. The theory requires that there be no average relative motion of the gas and liquid phases, hence the motivation for an experimental program in microgravity. The necessity of performing preliminary, Earth based experiments, however, requires performing experiments where the gas phase rises in the liquid, which significantly complicates the comparison of experiments with theory. Rather than comparing experimental results with theory for a uniform, homogeneous shear flow, experiments can be compared directly with solutions of the averaged equations of motion for bubble suspensions. This requires accounting for the significant lift force acting on the gas phase when the bubbles rise parallel to the average velocity of the sheared suspension. Shear flows can be produced in which the bubble phase pressure gradient, arising from shear induced collisions amongst the bubbles, balances a body force (centrifugal or gravitational) on the gas phase. A steady, non-uniform gas volume fraction can be measured, from which the bubble phase pressure gradient can be obtained and compared to theory and numerical simulations. The presence of bounding walls further complicates the experiments, since the detailed interactions of the bubbles with bounding walls is not well understood, especially in the presence of gravity, where the momentum and energy exchange depends on the inclination of the wall.
Building self-ordered tubular macro- and mesoporous nitridated titania from gas bubbles towards high-performance lithium-ion batteries.
Wang, Hai; Yang, Hongxing; Lu, Lin; Zhou, Yu; Wang, Yuanhao
Robust well-defined tubular structural materials based on macro- and mesoporous nitridated titania (TMMN-TiO2) were obtained by a simple solution-phase approach in ammonia solution. In this approach, the gas bubbles derived from ammonia solution play the role of templates that direct the ordered growth in the form of a tubular structure. The results demonstrated that the volume ratio of ammonia to water can be favorable for the formation of TMMN-TiO2, which are characterized by FESEM and FTIR. What is more, ammonia was used not only as the template but also as the nitrogen source. Interestingly, it was found that the TiO2 nanocrystals building blocks were assembled into an interconnected mesoporous skeleton and built in ordered tubular macroporous channels. This unique architecture provides many important features that are required for high-performance anodes, such as fast ion transport, high conductivity, and structure stability, thus enabling an electrode with outstanding lithium storage performance. For example, such an electrode delivers 112 mA h g(-1) capacity at 5100 mA g(-1) (30 C) even after 1200 cycles. PMID:23640367
Gas exchange across an air-water interface: experimental results and modeling of bubble contribution to transfer
Liliane Merlivat; Laurent Memery
Gas exchange experiments have been performed in a wind-water tunnel filled with fresh water or seawater. Transfer velocities have been measured for nitrous oxide and argon in a range of wind speeds extending from 3 m\\/s to 14 m\\/s. The air-liquid interface was covered either with only normally developed wind waves or with mechanically generated waves in addition. For u<9
Sonoluminescence and phase diagrams of single bubbles at low dissolved air concentrations I. Csabai,2
HorvÃth, êkos
Sonoluminescence and phase diagrams of single bubbles at low dissolved air concentrations G. Simon. INTRODUCTION Single bubble sonoluminescence SBSL is a phenom- enon where an acoustically levitated gas bubble bubble exhibit sonoluminescence SL only in a limited part of the (Pa ,R0 ,Ci /C0) parameter space 7
Molecular and atomic emission during single-bubble cavitation in concentrated sulfuric acid
Suslick, Kenneth S.
: April 12, 2005 1. Introduction A single gas bubble in a liquid can be acoustically levitated and driven and to the overall bubble oscillation will lead to a much more detailed understanding of SBSL. ˋ 2005 Acoustical,2 This light emission from single acoustically driven bubbles, dubbed single-bubble sonoluminescence (SBSL
Hydroacoustic experiments to establish a method for the determination of methane bubble fluxes at cold seeps
J. Greinert; B. N■tzel
Hydroacoustic methods are particularly suitable for investigations of the occurrence, cyclicity and amount of bubbles released at cold seeps without disturbing them. Experiments with a horizontally looking single beam transducer (40 and 300 kHz) directed towards artificially produced bubbles show that the backscattering strength of the bubbles increases with the gas flux rate independently of the bubble radii distribution. It is
The migration of a gas bubble under the action of surface tension and friction is dealt with numerically in some detail. The bubble is immersed in an infinitely extended liquid medium. Within the liquid there exists a constant temperature gradient far away from the bubble. Since surface tension decreases with increasing temperature, the bubble will move in the direction of
Fate of rising methane bubbles in stratified waters: How much methane reaches the atmosphere?
D. F. McGinnis; J. Greinert; Y. Artemov; S. E. Beaubien; A. W■est
There is growing concern about the transfer of methane originating from water bodies to the atmosphere. Methane from sediments can reach the atmosphere directly via bubbles or indirectly via vertical turbulent transport. This work quantifies methane gas bubble dissolution using a combination of bubble modeling and acoustic observations of rising bubbles to determine what fraction of the methane transported by
Metamorphism of stratified firn at Dome Fuji, Antarctica: A mechanism for local insolation modulation of gas transport conditions during bubble close off
NASA Astrophysics Data System (ADS)
Fujita, Shuji; Okuyama, Junichi; Hori, Akira; Hondoh, Takeo
The evolution of the structure of a 112.59 m long firn core recovered at Dome Fuji, East Antarctica, was investigated in order to improve understanding of firn densification and bubble formation processes, which are important for interpreting local insolation proxies used for astronomical dating of deep ice cores. Using selected samples, we measured physical properties including (1) the relative dielectric permittivities in both the vertical and horizontal planes, (2) the bulk density at a resolution of millimeters, (3) the three-dimensional geometric structure of pore space, and (4) crystal orientation fabrics. We found that the firn at Dome Fuji contains horizontal strata with thicknesses of several centimeters. Near the surface of the ice sheet, these strata are characterized by contrasting bulk density. Earlier field studies suggest that summer insolation causes densification of surface firn. Down to 30 m, density maxima exhibited a clear positive correlation with the strength of structural anisotropy and c axis clustering around the vertical. In contrast, the correlation is negative in deeper firn, confirming previous findings that initially less dense firn became denser than initially dense firn. In addition, numerous examples of textures indicating that deformation preferentially occurred in weaker layers were found. Moreover, the initially dense firn layers were more permeable for air near the bottom of firn. We propose a model linking firn properties with conditions for the gas transport processes near the bottom of firn. The model explains how stronger insolation can lead to bulk ice with a lower O2/N2 ratio and smaller total gas content.
Metamorphism of stratified firn at Dome Fuji, Antarctica: A mechanism for local insolation modulation of gas transport conditions during bubble close-off
NASA Astrophysics Data System (ADS)
Fujita, S.; Okuyama, J.; Hori, A.; Hondoh, T.
The evolution of the structure of a 112.59-m-long firn core recovered at Dome Fuji, East Antarctica, was investigated in order to improve understanding of firn densification and bubble formation processes, which are important for interpreting local insolation proxies used for astronomical dating of deep ice cores. Using selected samples, we measured physical properties including: (i) the relative dielectric permittivities in both the vertical and horizontal planes, (ii) the bulk density at a resolution of millimeters, (iii) the three-dimensional geometric structure of pore space, and (iv) crystal orientation fabrics. We found that the firn at Dome Fuji contains horizontal strata with thicknesses of several centimeters. Near the surface of the ice sheet, these strata are characterized by contrasting bulk density. Earlier field studies suggest that summer insolation causes densification of surface firn. Down to ~30 m, density maxima exhibited a clear positive correlation with the strength of structural anisotropy and c-axis clustering around the vertical. In contrast, the correlation is negative in deeper firn, confirming previous findings that initially less-dense firn became denser than initially dense firn. In addition, numerous examples of textures indicating that deformation preferentially occurred in weaker layers were found. Moreover, the initially dense firn layers were more permeable for air near the bottom of firn. We propose a model linking firn properties with conditions for the gas transport processes near the bottom of firn. The model explains how stronger insolation can lead to bulk ice with a lower O2/N2 ratio and smaller total gas content.
Heat transfer and bubble dynamics in slurry bubble columns for Fischer-Tropsch clean alternative energy
Chengtian Wu
With the increasing demand for alternative energy resources, the Fischer-Tropsch (FT) process that converts synthesis gas into clean liquid fuels has attracted more interest from the industry. Slurry bubble columns are the most promising reactors for FT synthesis due to their advantages over other reactors. Successful operation, design, and scale-up of such reactors require detailed knowledge of hydrodynamics, bubble dynamics,
Optimization of the bubble radius in a moving single bubble sonoluminescence
NASA Astrophysics Data System (ADS)
Mirheydari, Mona; Sadighi-Bonabi, Rasoul; Rezaee, Nastaran; Ebrahimi, Homa
A complete study of the hydrodynamic force on a moving single bubble sonoluminescence in N-methylformamide is presented in this work. All forces exerted, trajectory, interior temperature and gas pressure are discussed. The maximum values of the calculated components of the hydrodynamic force for three different radii at the same driving pressure were compared, while the optimum bubble radius was determined. The maximum value of the buoyancy force appears at the start of bubble collapse, earlier than the other forces whose maximum values appear at the moment of bubble collapse. We verified that for radii larger than the optimum radius, the temperature peak value decreases.
Comparison of steam-generator liquid holdup and core uncovery in two facilities of differing scale
Motley, F.; Schultz, R.
This paper reports on Run SB-CL-05, a test similar to Semiscale Run S-UT-8. The test results show that the core was uncovered briefly during the accident and that the rods overheated at certain core locations. Liquid holdup on the upflow side of the steam-generator tubes was observed. After the loop seal cleared, the core refilled and the rods cooled. These behaviors were similar to those observed in the Semiscale run. The Large-Scale Test Facility (LSTF) Run SB-CL-06 is a counterpart test to Semiscale Run S-LH-01. The comparison of the results of both tests shows similar phenomena. The similarity of phenomena in these two facilities build confidence that these results can be expected to occur in a PWR. Similar holdup has now been observed in the 6 tubes of Semiscale and in the 141 tubes of LSTF. It is now more believable that holdup may occur in a full-scale steam generator with 3000 or more tubes. These results confirm the scaling of these phenomena from Semiscale (1/1705) to LSTF (1/48). The TRAC results for SB-CL-05 are in reasonable agreement with the test data. TRAC predicted the core uncovery and resulting rod heatup. The liquid holdup on the upflow side of the steam-generator tubes was also correctly predicted. The clearing of the loop seal allowed core recovery and cooled the overheated rods just as it had in the data. The TRAC analysis results of Run SB-CL-05 are similar to those from Semiscale Run S-UT-8. The ability of the TRAC code to calculate the phenomena equally well in the two experiments of different scales confirms the scalability of the many models in the code that are important in calculating this small break.
Drop size distribution and holdup in a rotating impeller extraction column
Yong Kuk Lee; Dong Pyo Ju; Chul Kim
A stagewise hydrodynamic model, applying drop population balance equations derived from models for breakage and coalescence\\u000a of drops in a countercurrent liquid-liquid extraction system, was developed to predict the drop size distribution and the\\u000a holdup of the dispersed phase in a rotating impeller extraction column. The drop size distributions were obtained by taking\\u000a the photographs of the dispersions at the
Data Pre-Processing Method to Remove Interference of Gas Bubbles and Cell Clusters During Anaerobic and Aerobic Yeast Fermentations in a Stirred Tank Bioreactor
NASA Astrophysics Data System (ADS)
Princz, S.; Wenzel, U.; Miller, R.; Hessling, M.
One aerobic and four anaerobic batch fermentations of the yeast Saccharomyces cerevisiae were conducted in a stirred bioreactor and monitored inline by NIR spectroscopy and a transflectance dip probe. From the acquired NIR spectra, chemometric partial least squares regression (PLSR) models for predicting biomass, glucose and ethanol were constructed. The spectra were directly measured in the fermentation broth and successfully inspected for adulteration using our novel data pre-processing method. These adulterations manifested as strong fluctuations in the shape and offset of the absorption spectra. They resulted from cells, cell clusters, or gas bubbles intercepting the optical path of the dip probe. In the proposed data pre-processing method, adulterated signals are removed by passing the time-scanned non-averaged spectra through two filter algorithms with a 5% quantile cutoff. The filtered spectra containing meaningful data are then averaged. A second step checks whether the whole time scan is analyzable. If true, the average is calculated and used to prepare the PLSR models. This new method distinctly improved the prediction results. To dissociate possible correlations between analyte concentrations, such as glucose and ethanol, the feeding analytes were alternately supplied at different concentrations (spiking) at the end of the four anaerobic fermentations. This procedure yielded low-error (anaerobic) PLSR models for predicting analyte concentrations of 0.31 g/l for biomass, 3.41 g/l for glucose, and 2.17 g/l for ethanol. The maximum concentrations were 14 g/l biomass, 167 g/l glucose, and 80 g/l ethanol. Data from the aerobic fermentation, carried out under high agitation and high aeration, were incorporated to realize combined PLSR models, which have not been previously reported to our knowledge.
Measurement of the oil holdup for a two-phase oil-water flow through a sudden contraction in a horizontal pipe
NASA Astrophysics Data System (ADS)
Colombo, L. P. M.; Guilizzoni, M.; Sotgia, G. M.; Bortolotti, S.; Pavan, L.
Oil-water two-phase flow experiments were conducted in a horizontal duct made of PlexiglasÛ to determine the holdup of oil by means of the quick closing valves technique, using mineral oil (viscosity: 0.838 Pa s at 20 ¯C density: 890 kg m-3) and tap water. The duct presents a sudden contraction, with contraction ratio of 0.64. About 200 tests were performed by varying the flow rates of the phases. Flow patterns were investigated for both the up- and downstream pipe. Due to the relatively high value of the contraction ratio, it was not observed any relevant variation of the flow patterns across the sudden contraction. Data were then compared with predictions of a specific correlation for oil-water flow and some correlations for gas-water flow. A drift-flux model was also applied to determine the distribution parameter. The results agree quite well with flow pattern visualization.
Externally triggered renewed bubble nucleation in basaltic magma: The 12 October 2008 eruption at Halema`uma`u
Manga, Michael
additional bubbles in the shallow conduit leading to high number densities of small bubbles and (2) expanded this is manifested as continuous gas emission, gas pistoning, and lava spattering eruption styles [e.g., Edmonds
Effect of ultrasound on bubble breakup within the mixing chamber of an effervescent atomizer
T. K. Jagannathan; R. Nagarajan; K. Ramamurthi
Gas bubbles introduced into a liquid in the mixing chamber help to break up the liquid into fine droplets on being expanded to the ambient pressure. The passage of gas bubbles through the orifice of the nozzle requires that the size of the bubbles be much smaller than the diameter of the orifice. In the present work, the effectiveness of
CFD modeling of slurry bubble column reactors for FisherTropsch synthesis
Andrey A. Troshko; Franz Zdravistch
Industrial bubble column reactors for FischerTropsch (FT) synthesis include complex hydrodynamic, chemical and thermal interaction of three material phases: a population of gas bubbles of different sizes, a liquid phase and solid catalyst particles suspended in the liquid. In this paper, a CFD model of FT reactors has been developed, including variable gas bubble size, effects of the catalyst present
Bubble formation in microgravity
NASA Technical Reports Server (NTRS)
Antar, Basil N.
Two KC-135 flight campaigns have been conducted to date which are specifically dedicated to study bubble formation in microgravity. The first flight was conducted during March 14-18, 1994, and the other during June 20-24, 1994. The results from the June 1994 flight have not been analyzed yet, while the results from the March flight have been partially analyzed. In the first flight three different experiments were performed, one with the specific aim at determining whether or not cavitation can take place during any of the fluid handling procedures adopted in the shuttle bioprocessing experiments. The other experiments were concerned with duplicating some of the procedures that resulted in bubble formation, namely the NCS filling procedure and the needle scratch of a solid surface. The results from this set of experiments suggest that cavitation did not take place during any of the fluid handling procedures. The results clearly indicate that almost all were generated as a result of the breakup of the gas/liquid interface. This was convincingly demonstrated in the scratch tests as well as in the liquid fill tests.
Water Temperature Dependence of Single Bubble Sonoluminescence
Hilgenfeldt, S.; Lohse, D. [Fachbereich Physik der Universitaet Marburg, Renthof 6, D-35032 Marburg (Germany)] [Fachbereich Physik der Universitaet Marburg, Renthof 6, D-35032 Marburg (Germany); Moss, W.C. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
The strong dependence of the intensity of single bubble sonoluminescence (SBSL) on water temperature observed in experiment can be accounted for by the temperature dependence of the material constants of water, most essentially of the viscosity, of the argon solubility in water, and of the vapor pressure. The strong increase of light emission at low water temperatures is due to the possibility of applying higher driving pressures, caused by increased bubble stability. The presented calculations combine the Rayleigh-Plesset equation based hydrodynamical/chemical approach to SBSL and full gas dynamical calculations of the bubble{close_quote}s interior. {copyright} {ital 1998} {ital The American Physical Society}
Water temperature dependence of single bubble sonoluminescence
Sascha Hilgenfeldt; Detlef Lohse; Willy Moss
The strong dependence of the intensity of single bubble sonoluminescence (SBSL) on water temperature observed in experiment can be accounted for by the temperature dependence of the material constants of water, most essentially of the viscosity, of the argon solubility in water, and of the vapor pressure. The strong increase of light emission at low water temperatures is due to the possibility of applying higher driving pressures, caused by increased bubble stability. The presented calculations combine the Rayleigh-Plesset equation based hydrodynamical/chemical approach to SBSL and full gas dynamical calculations of the bubble's interior.
Molecular emission from single-bubble sonoluminescence
Yuri T. Didenko; William B. McNamara; Kenneth S. Suslick
Ultrasound can drive a single gas bubble in water into violent\\u000a oscillation; as the bubble is compressed periodically, extremely short\\u000a flashes of light (about 100 ps) are generated with clock-like\\u000a regularity(1-4). This process, known as single-bubble sonoluminescence,\\u000a gives rise to featureless continuum emission(4,5) in water (from 200 to\\u000a 800 nm, with increasing intensity into the ultraviolet). In contrast,\\u000a the emission
Screening of liquids for thermocapillary bubble movement
NASA Technical Reports Server (NTRS)
Wilcox, W. R.; Subramanian, R. S.; Papazian, J. M.; Smith, H. D.; Mattox, D. M.
Ground-based methods for pretesting qualitatively the thermocapillary movement of gas bubbles in a liquid to be used in space processing are discussed. Theoretical considerations are shown to require the use of a thin, enclosed, horizontal liquid film in order that the bubbles move faster than the bulk convection of the liquid, with insulating boundaries to prevent the onset of instabilities. Experimental realizations of horizontal cells in which to test the thermocapillary movement of bubbles in sheets of molten glass heated from below and organic melts in tubes heated from both ends are briefly described and the results of experiments are indicated.
Scale dependence of bubble creation mechanisms in breaking waves.
Deane, Grant B; Stokes, M Dale
Breaking ocean waves entrain air bubbles that enhance air-sea gas flux, produce aerosols, generate ambient noise and scavenge biological surfactants. The size distribution of the entrained bubbles is the most important factor in controlling these processes, but little is known about bubble properties and formation mechanisms inside whitecaps. We have measured bubble size distributions inside breaking waves in the laboratory and in the open ocean, and provide a quantitative description of bubble formation mechanisms in the laboratory. We find two distinct mechanisms controlling the size distribution, depending on bubble size. For bubbles larger than about 1 mm, turbulent fragmentation determines bubble size distribution, resulting in a bubble density proportional to the bubble radius to the power of -10/3. Smaller bubbles are created by jet and drop impact on the wave face, with a -3/2 power-law scaling. The length scale separating these processes is the scale where turbulent fragmentation ceases, also known as the Hinze scale. Our results will have important implications for the study of air-sea gas transfer. PMID:12192401
Acoustic waves in polydispersed bubbly liquids
NASA Astrophysics Data System (ADS)
Gubaidullin, D. A.; Gubaidullina, D. D.; Fedorov, Yu V.
The propagation of acoustic waves in polydispersed mixtures of liquid with two sorts of gas bubbles each of which has its own bubble size distribution function is studied. The system of the differential equations of the perturbed motion of a mixture is presented, the dispersion relation is obtained. Equilibrium speed of sound, low-frequency and high-frequency asymptotes of the attenuation coefficient are found. Comparison of the developed theory with known experimental data is presented.
Acoustic Energy Storage in Single Bubble Sonoluminescence
Michael P. Brenner; Sascha Hilgenfeldt; Detlef Lohse; Rodolfo R. Rosales
Single bubble sonoluminescence is understood in terms of a shock focusing towards the bubble center. We present a mechanism for significantly enhancing the effect of shock focusing, arising from the storage of energy in the acoustic modes of the gas. The modes with strongest coupling are not spherically symmetric. The storage of acoustic energy gives a framework for understanding how light intensities depend so strongly on ambient gases and liquids and suggests that the light intensities of successive flashes are highly correlated.
Superabsorption of acoustic waves with bubble metascreens
NASA Astrophysics Data System (ADS)
Leroy, Valentin; Strybulevych, Anatoliy; Lanoy, Maxime; Lemoult, Fabrice; Tourin, Arnaud; Page, John H.
A bubble metascreen, i.e., a single layer of gas inclusions in a soft solid, can be modeled as an acoustic open resonator, whose behavior is well captured by a simple analytical expression. We show that by tuning the parameters of the metascreen, acoustic superabsorption can be achieved over a broad frequency range, which is confirmed by finite element simulations and experiments. Bubble metascreens can thus be used as ultrathin coatings for turning acoustic reflectors into perfect absorbers.
Single Bubble Sonoluminescence in Low Gravity and Optical Radiation Pressure Positioning of the Bubble
NASA Technical Reports Server (NTRS)
Thiessen, D. B.; Young, J. E.; Marr-Lyon, M. J.; Richardson, S. L.; Breckon, C. D.; Douthit, S. G.; Jian, P. S.; Torruellas, W. E.; Marston, P. L.
Several groups of researchers have demonstrated that high frequency sound in water may be used to cause the regular repeated compression and luminescence of a small bubble of gas in a flask. The phenomenon is known as single bubble sonoluminescence (SBSL). It is potentially important because light emitted by the bubble appears to be associated with a significant concentration of energy within the volume of the bubble. Unfortunately, the detailed physical mechanisms causing the radiation of light by oscillating bubbles are poorly understood and there is some evidence that carrying out experiments in a weightless environment may provide helpful clues. In addition, the radiation pressure of laser beams on the bubble may provide a way of simulating weightless experiments in the laboratory. The standard model of SBSL attributes the light emission to heating within the bubble by a spherically imploding shock wave to achieve temperatures of 50,000 K or greater. In an alternative model, the emission is attributed to the impact of a jet of water which is required to span the bubble and the formation of the jet is linked to the buoyancy of the bubble. The coupling between buoyancy and jet formation is a consequence of the displacement of the bubble from a velocity node (pressure antinode) of the standing acoustic wave that drives the radial bubble oscillations. One objective of this grant is to understand SBSL emission in reduced buoyancy on KC-135 parabolic flights. To optimize the design of those experiments and for other reasons which will help resolve the role of buoyancy, laboratory experiments are planned in simulated low gravity in which the radiation pressure of laser light will be used to position the bubble at the acoustic velocity node of the ultrasonic standing wave. Laser light will also be used to push the bubble away from the velocity node, increasing the effective buoyancy. The original experiments on the optical levitation and radiation pressure on bubbles in water by Unger and Marston noted above were carried out using a continuous wave (CW) beam of an Argon laser. For lateral stability the beam had a intensity minimum along its axis. Calculations of the optical radiation force on an SBSL bubble indicate that ion laser technology is a poor choice for providing the magnitude of the average optical radiation force required. Consequently it is necessary to examine various diode-pumped solid state laser technologies. The approach for this part of the research will be to achieve optical levitation of a quiescent bubble based on contemporary laser technology and then to strobe the laser synchronously with the SBSL bubble oscillations.
Methane bubbles trapped in thermokarst lake ice
When ice-rich permafrost thaws, former tundra and forest turns into a thermokarst lake as the ground subsides. The carbon stored in the formerly frozen ground is consumed by the microbial community, who release methane gas. When lake ice forms in the winter, methane gas bubbles are trapped in the ic...
Bubble evolution and properties in homogeneous nucleation simulations.
AngÕlil, Raymond; Diemand, J■rg; Tanaka, Kyoko K; Tanaka, Hidekazu
We analyze the properties of naturally formed nanobubbles in Lennard-Jones molecular dynamics simulations of liquid-to-vapor nucleation in the boiling and the cavitation regimes. The large computational volumes provide a realistic environment at unchanging average temperature and liquid pressure, which allows us to accurately measure properties of bubbles from their inception as stable, critically sized bubbles, to their continued growth into the constant speed regime. Bubble gas densities are up to 50% lower than the equilibrium vapor densities at the liquid temperature, yet quite close to the gas equilibrium density at the lower gas temperatures measured in the simulations: The latent heat of transformation results in bubble gas temperatures up to 25% below those of the surrounding bulk liquid. In the case of rapid bubble growth-typical for the cavitation regime-compression of the liquid outside the bubble leads to local temperature increases of up to 5%, likely significant enough to alter the surface tension as well as the local viscosity. The liquid-vapor bubble interface is thinner than expected from planar coexistence simulations by up to 50%. Bubbles near the critical size are extremely nonspherical, yet they quickly become spherical as they grow. The Rayleigh-Plesset description of bubble-growth gives good agreement in the cavitation regime. PMID:25615216
Bubble evolution and properties in homogeneous nucleation simulations
NASA Astrophysics Data System (ADS)
AngÕlil, Raymond; Diemand, J■rg; Tanaka, Kyoko K.; Tanaka, Hidekazu
We analyze the properties of naturally formed nanobubbles in Lennard-Jones molecular dynamics simulations of liquid-to-vapor nucleation in the boiling and the cavitation regimes. The large computational volumes provide a realistic environment at unchanging average temperature and liquid pressure, which allows us to accurately measure properties of bubbles from their inception as stable, critically sized bubbles, to their continued growth into the constant speed regime. Bubble gas densities are up to 50 % lower than the equilibrium vapor densities at the liquid temperature, yet quite close to the gas equilibrium density at the lower gas temperatures measured in the simulations: The latent heat of transformation results in bubble gas temperatures up to 25 % below those of the surrounding bulk liquid. In the case of rapid bubble growthtypical for the cavitation regimecompression of the liquid outside the bubble leads to local temperature increases of up to 5 %, likely significant enough to alter the surface tension as well as the local viscosity. The liquid-vapor bubble interface is thinner than expected from planar coexistence simulations by up to 50 % . Bubbles near the critical size are extremely nonspherical, yet they quickly become spherical as they grow. The Rayleigh-Plesset description of bubble-growth gives good agreement in the cavitation regime.
Characterizing the liquid dynamics in cocurrent gasliquid flows in porous media using twin-plane electrical capacitance tomography
M. Hamidipour; F. Larachi
The hydrodynamics of gasliquid cocurrent down- and upflow packed beds was studied experimentally using twin-plane electrical capacitance tomography (ECT). The ability of ECT to measure liquid holdups was examined by performing different calibration procedures. Confrontation of liquid holdup measurements from single-\\/twin-plane ECT, RTD and bed drainage revealed that ECT calibration between pre-wetted and flooded bed captured accurately the free-draining liquid
6/10/12 Researchers Develop New Method to Measure Bubble Size Distribution in Pipelines 1/2www.azomining.com/news.aspx?newsID=6367
Sû°bester, AndrûÀs
6/10/12 Researchers Develop New Method to Measure Bubble Size Distribution in Pipelines 1/2www | | Svenska Researchers Develop New Method to Measure Bubble Size Distribution in Pipelines Published on May and developed a new process to precisely measure gas bubbles present in pipelines. Measuring gas bubbles
Bubble Growth and Detachment from a Needle
NASA Astrophysics Data System (ADS)
Shusser, Michael; Rambod, Edmond; Gharib, Morteza
The release of bubbles from an underwater nozzle or orifice occurs in large number of applications, such as perforated plate columns, blood oxygenators and various methods of water treatment. It is also a widely used method in laboratory research on multiphase flow and acoustics for generating small bubbles in a controlled fashion. We studied experimentally the growth and pinch-off of air bubbles released from a submerged needle into a quiescent liquid or a liquid flowing parallel to the needle. Micron-sized bubbles were generated by an air-liquid dispenser. High-speed imaging was performed to study the formation and detachment of bubbles from the tip of the needle. The impact of the needle diameter was investigated and the size and number of produced bubbles were assessed for different flow rates of air and for different velocities of the imposed upward liquid flow. The results were compared with available theoretical models and numerical computations. The existence of a critical gas flow rate and two regimes of bubble growth were verified.
Acoustic Bubble Removal from Boiling Surfaces
NASA Technical Reports Server (NTRS)
Prosperetti, Andrea
The object of the study was the investigation of the forces generated by standing acoustic waves on vapor bubbles, both far and near boundaries. In order to accomplish this objective, in view of the scarcity of publications on the topic, it has been necessary to build an edifice of knowledge about vapor bubbles in sound and flow fields from the ground up, as it were. We have addressed problems of gradually greater difficulty as follows: 1. In the first place, the physics of an stationary isolated bubble subject to a sound field in an unbounded liquid was addressed; 2. The case of bubbles translating in a stationary pressure field was then considered; 3. This was followed by a study of the combined effects of sound and translation, 4. And of a neighboring boundary 5. Finally, a new method to deal with nonspherical bubbles was developed- In addition to the work on vapor bubbles, some studies on gas bubbles were conducted in view of NASA's interest in the phenomenon of sonoluminescence.
Mechanisms of stability of armored bubbles: FY 1996 Final Report
W. R. Rossen; S. I. Kam
Theoretical and experimental studies examine how a coating, or {open_quotes}armor,{close_quotes} of partially wetted solid particles can stabilize tiny bubbles against diffusion of gas into the surrounding liquid, in spite of the high capillary pressures normally associated with such bubbles. Experiments with polymethylmethacrylate (PNMA) beads and carbonated water demonstrate that armored bubbles can persist for weeks in liquid unsaturated with respect
Molecular dynamics simulations of cavitation bubble collapse and sonoluminescence
NASA Astrophysics Data System (ADS)
Schanz, Daniel; Metten, Burkhard; Kurz, Thomas; Lauterborn, Werner
The dynamics of the medium within a collapsing and rebounding cavitation bubble is investigated by means of molecular dynamics (MD) simulations adopting a hard sphere model for the species inside the bubble. The dynamics of the surrounding liquid (water) is modelled using a Rayleigh-Plesset (RP)-type equation coupled to the bubble interior by the gas pressure at the wall obtained from the MD calculations. Water vapour and vapour chemistry are included in the RP-MD model as well as mass and energy transfer through the bubble wall. The calculations reveal the evolution of temperature, density and pressure within a bubble at conditions typical of single-bubble sonoluminescence and predict how the particle numbers and densities of different vapour dissociation and reaction products in the bubble develop in space and time. Among the parameters varied are the sound pressure amplitude of a sonoluminescence bubble in water, the noble gas mixture in the bubble and the accommodation coefficients for mass and energy exchange through the bubble wall. Simulation particle numbers up to 10 million are used; most calculations, however, are performed with one million particles to save computer run time. Validation of the MD code was done by comparing MD results with solutions obtained by continuum mechanics calculations for the Euler equations.
Bubble Manipulation by Self Organization of Bubbles inside Ultrasonic Wave
NASA Astrophysics Data System (ADS)
Yamakoshi, Yoshiki; Koganezawa, Masato
Microbubble manipulation using ultrasonic waves is a promising technology in the fields of future medicine and biotechnology. For example, it is considered that bubble trapping using ultrasonic waves may play an important role in drug or gene delivery systems in order to trap the drugs or genes in the diseased tissue. Usually, when bubbles are designed so that they carry payloads, such as drug or gene, they tend to be harder than free bubbles. These hard bubbles receive a small acoustic radiation force, which is not sufficient for bubble manipulation. In this paper, a novel method of microbubble manipulation using ultrasonic waves is proposed. This method uses seed bubbles in order to manipulate target bubbles. When the seed bubbles are introduced into the ultrasonic wave field, they start to oscillate to produce a bubble aggregation of a certain size. Then the target bubbles are introduced, the target bubbles attach around the seed bubbles producing a bubble mass with bilayers (inner layer: seed bubbles, outer layer: target bubbles). The target bubbles are manipulated as a bilayered bubble mass. Basic experiments are carried out using polyvinyl chloride (PVC) shell bubbles. No target bubbles are trapped when only the target bubbles are introduced. However, they are trapped if the seed bubbles are introduced in advance.
Nonlinear Photon Bubbles Driven by Buoyancy
Mitchell C. Begelman
We derive an analytic model for nonlinear "photon bubble" wave trains driven by buoyancy forces in magnetized, radiation pressure-dominated atmospheres. Continuous, periodic wave solutions exist when radiative diffusion is slow compared to the dynamical timescale of the atmosphere. We identify these waves with the saturation of a linear instability discovered by Arons - therefore, these wave trains should develop spontaneously. The buoyancy-driven waves are physically distinct from photon bubbles in the presence of rapid diffusion, which evolve into trains of gas pressure-dominated shocks as they become nonlinear. Like the gas pressure-driven shock trains, buoyancy-driven photon bubbles can exhibit very large density contrasts, which greatly enhance the flow of radiation through the atmosphere. However, steady-state solutions for buoyancy-driven photon bubbles exist only when an extra source of radiation is added to the energy equation, in the form of a flux divergence. We argue that this term is required to compensate for the radiation flux lost via the bubbles, which increases with height. We speculate that an atmosphere subject to buoyancy-driven photon bubbles, but lacking this compensating energy source, would lose pressure support and collapse on a timescale much shorter than the radiative diffusion time in the equivalent homogeneous atmosphere.
Sonoluminescing bubbles and mass diffusion
Loefstedt, R.; Weninger, K.; Putterman, S.; Barber, B.P. [Department of Physics, University of California, Los Angeles, California 90024 (United States)] [Department of Physics, University of California, Los Angeles, California 90024 (United States)
The transduction of sound into light by a pulsating bubble in water occurs when its maximum radius is about ten times greater than its ambient radius. For such high-amplitude motion, the steady-state balance of mass flow between the bubble and gas dissolved in the surrounding fluid can be maintained by diffusion only at low partial pressures, about 3 Torr. The observation of sonoluminescence (SL) from bubbles in 200 Torr solutions of air in water requires the action of some as yet unknown mass flow mechanism. On the other hand, gas solutions prepared at low partial pressures, in the diffusion-controlled regime, enable one to achieve SL in gases that do not emit light at higher partial pressures. These include hydrogenic gases and gases with a ratio of specific heats close to unity, which hardly heat up upon adiabatic compression. Experiments that probe the role of mass transfer in SL are presented along with the implications of their comparison to a multiple-time-scale analysis of mass diffusion.
Methods for nondestructive assay holdup measurements in shutdown uranium enrichment facilities
Hagenauer, R.C.; Mayer, R.L. II.
Measurement surveys of uranium holdup using nondestructive assay (NDA) techniques are being conducted for shutdown gaseous diffusion facilities at the Oak Ridge K-25 Site (formerly the Oak Ridge Gaseous Diffusion Plant). When in operation, these facilities processed UF{sub 6} with enrichments ranging from 0.2 to 93 wt % {sup 235}U. Following final shutdown of all process facilities, NDA surveys were initiated to provide process holdup data for the planning and implementation of decontamination and decommissioning activities. A three-step process is used to locate and quantify deposits: (1) high-resolution gamma-ray measurements are performed to generally define the relative abundances of radioisotopes present, (2) sizable deposits are identified using gamma-ray scanning methods, and (3) the deposits are quantified using neutron measurement methods. Following initial quantitative measurements, deposit sizes are calculated; high-resolution gamma-ray measurements are then performed on the items containing large deposits. The quantitative estimates for the large deposits are refined on the basis of these measurements. Facility management is using the results of the survey to support a variety of activities including isolation and removal of large deposits; performing health, safety, and environmental analyses; and improving facility nuclear material control and accountability records. 3 refs., 1 tab.
Flow regime transition in bubble columns
Krishna, R.; Ellenberger, J.; Maretto, C. [Univ. of Amsterdam (Netherlands). Dept. of Chemical Engineering] [Univ. of Amsterdam (Netherlands). Dept. of Chemical Engineering
The various factors influencing the regime transition point in gas-liquid bubble columns are examined. Increasing gas density delays regime transition. This phenomenon is described in a qualitative way by the correlations of Reilly and Wilkinson of which the Reilly correlation is found to be more accurate. However, both correlations are unable to account for the influence of the addition of small quantities of surface tension reducing agents. The Reilly and Wilkinson correlations are also not adequate to describe the influence of the addition of catalyst particles on the transition point for a bubble column slurry reactor.
Potential uses of vacuum bubbles in noise and vibration control
Istvan L. Ver
Vacuum bubbles are new acoustic elements which are dynamically more compliant than the gas volume they replace, but which are statically robust. They are made of a thin metallic shell with vacuum in their cavity. Consequently, they pose no danger in terms of contamination or fire hazard. The potential of the vacuum bubble concept for noise and vibration control was
Bubbles interactions in the cahn-hilliard equation
Calisto; Clerc; Rojas; Tirapegui
We study the dynamics of bubbles in the one dimensional Cahn-Hilliard equation. For a gas of diluted bubbles we find ordinary differential equations describing their interaction which permits us to describe the ulterior dynamics of the system in very good agreement with numerical simulations. PMID:11041932
NSDL National Science Digital Library
Brieske, Joel A.
The first Web site, from The Soap and Detergent Association, is called Soaps and Detergents (1). Visitors learn about the chemistry of soap and detergent, their history, how they're manufactured, and more. The easily read text and fun illustrations make this site a great place to start for this topic. The next site, called Bubble Engineering (2), is provided by Bubble Town. The page describes the physics of a cone-shaped bubble blowing device and how its shape reduces the velocity of air being blown through but not the volume of air moving through it. Other links on the site describe what the contents of the best bubble soap mixture. The third site is provided by Kevin Dunn of Hampden-Sydney College Department of Chemistry called Lye Soap (3). The site describes how soap was invented, the chemistry of lye and soap, how to make your own lye, and more. The fourth site highlighted is part of LessonPlansPage.com called Looking at Bubbles (4). The site, which is a lesson plan, is geared towards students between grades 6 and 8. The main objective of the chemistry activity is to explore what things can be added to soap to make the bubbles last longer. All procedures are provided to view online or to print. The Art and Science of Bubbles (5) Web site is maintained by the Soap and Detergent Association. Many great features can be found on this and other pages within the site, including washing hands with soap, the history and chemistry of soaps and detergents, the environmentally smart way of using and disposing of cleaning products, and more. The sixth site related to soap is entitled Bubble Games (6), which is maintained by bubbles.org. Three free games are offered here including Tic-Tac-Bubble, Bubblechase, and Bubble Wrap, which counts how many bubbles you can pop in twenty seconds. Next, from the Homeschooling page of About.com comes the Soap Power (7) activity. This unique lesson plan details how to power a model boat using soap as a result of its surface tension. Lastly, the Bubble Hydrodynamics (8) Web site is maintained by bubbleology.com. Visitors get an introduction to bubble hydrodynamics and also learn about the relationship between temperature and bubbles, surfactants and bubbles, and even oscillations and bubbles.
Interaction of lithotripter shockwaves with single inertial cavitation bubbles
Klaseboer, Evert; Fong, Siew Wan; Turangan, Cary K.; Khoo, Boo Cheong; Szeri, Andrew J.; Calvisi, Michael L.; Sankin, Georgy N.; Zhong, Pei
The dynamic interaction of a shockwave (modelled as a pressure pulse) with an initially spherically oscillating bubble is investigated. Upon the shockwave impact, the bubble deforms non-spherically and the flow field surrounding the bubble is determined with potential flow theory using the boundary-element method (BEM). The primary advantage of this method is its computational efficiency. The simulation process is repeated until the two opposite sides of the bubble surface collide with each other (i.e. the formation of a jet along the shockwave propagation direction). The collapse time of the bubble, its shape and the velocity of the jet are calculated. Moreover, the impact pressure is estimated based on water-hammer pressure theory. The Kelvin impulse, kinetic energy and bubble displacement (all at the moment of jet impact) are also determined. Overall, the simulated results compare favourably with experimental observations of lithotripter shockwave interaction with single bubbles (using laser-induced bubbles at various oscillation stages). The simulations confirm the experimental observation that the most intense collapse, with the highest jet velocity and impact pressure, occurs for bubbles with intermediate size during the contraction phase when the collapse time of the bubble is approximately equal to the compressive pulse duration of the shock wave. Under this condition, the maximum amount of energy of the incident shockwave is transferred to the collapsing bubble. Further, the effect of the bubble contents (ideal gas with different initial pressures) and the initial conditions of the bubble (initially oscillating vs. non-oscillating) on the dynamics of the shockwavebubble interaction are discussed. PMID:19018296
Electrowetting of soap bubbles
NASA Astrophysics Data System (ADS)
Arscott, Steve
A proof-of-concept demonstration of the electrowetting-on-dielectric of a sessile soap bubble is reported here. The bubbles are generated using a commercial soap bubble mixturethe surfaces are composed of highly doped, commercial silicon wafers covered with nanometer thick films of TeflonÛ. Voltages less than 40 V are sufficient to observe the modification of the bubble shape and the apparent bubble contact angle. Such observations open the way to inter alia the possibility of bubble-transport, as opposed to droplet-transport, in fluidic microsystems (e.g., laboratory-on-a-chip)the potential gains in terms of volume, speed, and surface/volume ratio are non-negligible.
Shock-Wave-Induced Jetting of Micron-Size Bubbles
NASA Astrophysics Data System (ADS)
Ohl, C. D.; Ikink, R.
Free gas bubbles in water with radii between 7 and 55 ?m subjected to a shock wave exhibit a liquid jetting phenomenon with the jet pointing in the direction of the propagating shock wave. With increasing bubble radius, the length of the jet tip increases and a lower estimate of the averaged jet velocity increases linearly from 20 to 150 m/s. At a later stage, the jet breaks up and releases micron-size bubbles. In the course of shock wave permeabilization and transfection of biological cells, this observation suggests a microinjection mechanism when the cells are near bubbles exposed to a shock wave.
Diffusive Migration of Mass in Bubbly Media
Goldobin, Denis S
We consider a liquid bearing gas bubbles. When gas bubbles are immovably trapped in a porous matrix by surface tension forces, the dominant mechanism of transfer of gas mass becomes the diffusion of gas molecules through the liquid. Essential, the gas solution is in local thermodynamic equilibrium with vapour phase all over the system, i.e. the solute concentration equals the solubility. When the temperature and/or pressure gradients are applied, the diffusion fluxes appear and these fluxes are faithfully determined by the temperature and pressure fields, not by the local solute concentration. We derive the equations governing such systems, accounting for thermodiffusion and gravitational buoyancy effects which are shown not to be neglected for geological systems. The results are applied for treatment of non-high pressure systems and real geological systems bearing methane or carbon dioxide. The reported effects are of particular importance for methane-hydrate deposits and the problem of burial of industrial ...
NSDL National Science Digital Library
In this experiment, learners use JOY liquid detergent and glycerin to make the largest bubble they can that lasts 15 seconds. They blow the bubbles in a Teaching Tank, a narrow tank that is commercially available, which allows them to easily measure and monitor the bubbles. Results are collected and graphed by learners. Questions and teaching notes are included to encourage learners to consider what the multiple variables are, and what the effects of sugar, corn syrup, or other sweeteners are on their bubbles.
Measurements of the average properties of a suspension of bubbles rising in a vertical channel
NASA Astrophysics Data System (ADS)
Zenit, Roberto; Koch, Donald L.; Sangani, Ashok S.
Experiments were performed in a vertical channel to study the behaviour of a monodisperse bubble suspension for which the dual limit of large Reynolds number and small Weber number was satisfied. Measurements of the liquid-phase velocity fluctuations were obtained with a hot-wire anemometer. The gas volume fraction, bubble velocity, bubble velocity fluctuations and bubble collision rate were measured using a dual impedance probe. Digital image analysis was performed to quantify the small polydispersity of the bubbles as well as the bubble shape.
Generation of single bubbles of various sizes using a slitting elastic tube
NASA Astrophysics Data System (ADS)
Sanada, T.; Abe, K.
The generation of single bubbles is often required in laboratory research. However, it is very difficult to control bubble production, especially for a required bubble size, by using the same orifice. In this study, we demonstrate the control of bubble formation by combining a pulsed acoustic pressure wave in a gas phase and a slitting elastic tube. By elastically deforming the tube using the acoustic wave, we can control the bubble radius in the range from 300 ?m to 5 mm by using the same tube without liquid flow. This method can produce bubbles with good repeatability and small individual differences in the tubes.
Quantitative measurement of argon inside of nano-sized bubbles in ODS steels
NASA Astrophysics Data System (ADS)
Klimenkov, M.
Quantitative analysis of Ar gas in nano-sized bubbles in ODS steel was performed using spatially resolved energy-dispersive X-ray spectroscopy. The Ar K? line was quantified and used for calculation of Ar the concentration (atoms per nm 3) inside 4-38 nm large bubbles. The Ar concentration and pressure inside bubbles were found to depend on the bubble size. The results were compared with a known equilibrium pressure model developed for calculation of He pressure inside nano-sized bubbles. Several investigations were performed to determine the stability of Ar bubbles in the thin TEM foil.
Polydispersed solids behavior in a bubble column. [Slurry bubble columns
Smith, D.N.; Ruether, J.A.; Stiegel, G.J.
New data and theory are presented for describing polydispersed solids in slurry bubble columns. Axial solids concentration distributions were measured in a 0.108-m-ID slurry bubble column apparatus operated at steady-state conditions. Slurry and gas superficial velocities ranged from 0.007 to 0.02 m/s and 0.03 to 0.20 m/s, respectively. The liquid phase was water and the solid phase consisted of binary or ternary mixtures of narrow-sized fractions of glass spheres. The experimental data have been used to develop a method for predicting average solids loadings and axial distributions of solids in a bubble column with a one-dimensional sedmentation-dispersion model. Correlations are given for the hindered settling velocity, the solids dispersion coefficient, and the solids concentration at the top and bottom of the column. The effect of a distribution of particle size is interpreted by summation of the concentration of solids for each discrete particle size fraction. 12 refs., 13 figs.
Water-Splitting Photoelectrolysis Reaction Rate via Microscopic Imaging of Evolved Oxygen Bubbles
Atwater, Harry
Water-Splitting Photoelectrolysis Reaction Rate via Microscopic Imaging of Evolved Oxygen Bubbles of the gas-evolving reaction rate. Optical microscopy was used to record the bubble growth on single a focused argon laser. By analyzing the bubble size as a function of time, the water-splitting reaction rate
Decay rates of oscillations and effective heat transfer coefficients for bubbles pulsating radially in a liquid
R. I. Nigmatulin; N. S. Khabeev
Vapor (gas) bubbles executing free radial oscillations in a liquid are considered. Expressions are obtained for the frequency and decay rate of small free oscillations of the bubbles. The effective coefficients of heat transfer between the radially pulsating bubbles and the liquid are determined.
Bubble flow and the formation of cavity defect in weld pool of vacuum electron beam welding
Yi Luo; Jinhe Liu; Hong Ye
Seen from gas-liquid two-phase-flow system, the gas phase and liquid phase of bubble flow in weld pool are studied by means of isolated phase based on the conservation of mass and momentum. The two-dimensional fractional flow model of bubble flow in weld pool of vacuum electron beam welding is developed. And the gas distribution and the phenomenon of bubble flow
Contact time of a pair of bubbles in an acoustic field
NASA Astrophysics Data System (ADS)
Shirota, Minori; Miyamae, Hiroki
Contact time of a pair of bubbles in an acoustic field is investigated experimentally. Pairs of bubbles of about 0.1 mm in radius were exposed in an acoustic field of about 30 kHz. The bubbles were generated at T-shaped microfluidic junction in silicone oil of 50 cSt with actively controlled gas pressure change. These bubbles were then introduced into an acoustic levitator commonly used in single bubble sonoluminescence experiment. The contact time of the oscillating bubbles were quantitatively evaluated using high-speed imaging technique. Bubbles with in-phase volume oscillation attracted each other due to secondary Bjerknes force and finally coalesced. We observed bubbles smaller than resonant sizes at large separate distance deforms greatly and coalesced immediately when they touch, while bubbles of the resonant sizes were kept contacting such long time as over 100 periods of forcing.
Original paper Soap Bubble Clusters
Taylor, Jean
Original paper Soap Bubble Clusters Fred ALMGREN surface, soap bubbles Abstract. This article reviews the theorems from geometric measure theory which guarantee the existence and give the structure of mathematical models of soap bubble clusters. It also
Effect of the Rayleigh-Taylor instability on maximum reachable temperatures in laser-induced bubbles
NASA Astrophysics Data System (ADS)
Rechiman, Ludmila M.; Bonetto, FabiÃn J.; Rossellµ, Juan M.
Laser-induced bubbles provide an effective vehicle to achieve high-energy concentrations and maximum temperatures in bubble luminescence phenomena. One limitation to the temperatures that can be achieved is the development of the Rayleigh-Taylor instability (RTI) during the instants previous to the bubble maximum compression. For a given fluid, the control parameters of the experiment are: the bubble maximum radius, the bubble ambient radius, the initial perturbations of the bubble, and the liquid pressure at infinity. In this work, experiments using laser-induced bubbles in a highly viscous phosphoric acid were performed in order to determine the achievable parameters values in the phase space. The effect of Rmax, R0, a2i, a3i, and p? on the maximum temperature achieved by the gas contents inside the bubble were numerically determined. The results show for each static pressure an optimum region for maximum temperatures of the gas contents bounded by the RTI.
Effective Compressibility of a Bubbly Slurry.
Kam, S. I.; Gauglitz, P. A.; Rossen, W. R.
Bubbles trapped within the slurry at the bottom of waste tanks at the Hanford Site expand and contract in response to ambient pressure changes. These bubbles contain hydrogen and other flammable gases that can pose a safety hazard. Determining the effective compressibility of bubbles in the slurry could allow one to make improved estimates of the quantity of gas trapped in the slurry from changes in slurry volume with ambient pressure changes. More broadly, the diffusive growth and mechanical properties of bubbles in a porous medium are important issues in a number of applications. Numerical calculations based on a one-dimensional biconical-pore-network model show that the effective compressibility of a population of bubbles shows hysteresis with pressure increase and decrease. This hysteresis is caused by the sudden jumps of interfaces from pore throat to throat during a pressure decrease and from pore body to body during a pressure increase. Snap-off may occur during these jumps but does not significantly alter the effective compressibility of the population of bubbles. Copyright 2001 Academic Press. PMID:11502127
A two-compartment convective-diffusion model for slurry bubble column reactors
S. Degaleesan; M. P. Dudukovic; B. A. Toseland; B. L. Bhatt
Synthesis gas can be made from a variety of coal, natural gas, environmentally distressed materials such as petroleum coke and biomass. There are considerable reactor design and scale-up problems associated with synthesis gas conversion technologies which arise due to the special characteristics of these processes. Bubble columns and slurry bubble column reactors (SBCRs), due to their superior heat transfer characteristics,
On the thermocapillary motion of a bubble in a low gravitational environment
J. Siekmann; J. Szymczyk
A numerical model is developed for the motion of a gas bubble immersed in a liquid with a constant spatial temperature gradient and experiencing surface tension forces and friction. The gradient alters the surface tension at the gas-liquid interface, producing a tangential force at the gas-liquid interface and motions inside and outside of the bubble. Marangoni convection appears and the
Unsteady thermocapillary migration of bubbles
NASA Technical Reports Server (NTRS)
Dill, Loren H.; Balasubramaniam, R.
Upon the introduction of a gas bubble into a liquid possessing a uniform thermal gradient, an unsteady thermo-capillary flow begins. Ultimately, the bubble attains a constant velocity. This theoretical analysis focuses upon the transient period for a bubble in a microgravity environment and is restricted to situations wherein the flow is sufficiently slow such that inertial terms in the Navier-Stokes equation and convective terms in the energy equation may be safely neglected (i.e., both Reynolds and Marangoni numbers are small). The resulting linear equations were solved analytically in the Laplace domain with the Prandtl number of the liquid as a parameter; inversion was accomplished numerically using a standard IMSL routine. In the asymptotic long-time limit, the theory agrees with the steady-state theory of Young, Goldstein, and Block. The theory predicts that more than 90 percent of the terminal steady velocity is achieved when the smallest dimensionless time, i.e., the one based upon the largest time scale-viscous or thermal-equals unity.
Direct perfluorination of K(2)B(12)H(12) in acetonitrile occurs at the gas bubble-solution interface and is inhibited by HF. Experimental and DFT study of inhibition by protic acids and soft, polarizable anions.
Peryshkov, Dmitry V; Popov, Alexey A; Strauss, Steven H
During the optimization of the F(2) perfluorination of K(2)B(12)H(12) in acetonitrile with continuous bubbling of 20/80 F(2)/N(2), it was discovered that (i) HF and other protic acids inhibit each of the 12 fluorination steps (in contradiction to recently published findings) and (ii) the fluorinations appear to take place at the gas bubble-solution interface. Experimental results and DFT calculations suggest that these two phenomena are related by the relative propensities of the various B(12)H(12-x)F(x)(2-) anions to partition from bulk solution to the interface (i.e., their relative polarizabilities or softness; 0
Bubble behavior in molten glass in a temperature gradient. [in reduced gravity rocket experiment
NASA Technical Reports Server (NTRS)
Meyyappan, M.; Subramanian, R. S.; Wilcox, W. R.; Smith, H.
Gas bubble motion in a temperature gradient was observed in a sodium borate melt in a reduced gravity rocket experiment under the NASA SPAR program. Large bubbles tended to move faster than smaller ones, as predicted by theory. When the bubbles contacted a heated platinum strip, motion virtually ceased because the melt only imperfectly wets platinum. In some cases bubble diameter increased noticeably with time.
The mass and energy of a vapor bubble in a turbulent ideal fluid
Valery P. Dmitriyev
The mass of a bubble in a fluid can be taken as the mass of the vapor in it. The self-energy of the bubble is defined as the work performed against the pressure of the fluid in order to create the bubble. Taking the vapor to be an ideal gas the relationship between the self-energy, the mass of the bubble and the speed of the perturbation wave in a turbulent ideal fluid can be obtained.
Dye-bubble interactions in an open channel flow
NASA Astrophysics Data System (ADS)
Crepeau, John C.; McIlroy, Hugh M.
An innovative technique has been developed to visualize the effect that a localized surface reaction has in an open channel flow field. The working fluid is hexanoic acid mixed with mineral oil, and it flows over an aluminum plate embedded with sodium metal. Hexanoic acid and sodium metal react to form hydrogen gas and hexanoic salt. The hydrogen gas forms bubbles that rise to the surface and are convected downstream by the fluid. The rising bubbles induce the formation of counter-rotating vortices that straddle the reaction site. Bubble entrainment stretches and bends the dye filaments, and buoyancy transports the bubbles away from the reaction. The products of the reaction introduce velocity fluctuations into an otherwise laminar flow, inducing what has been described by some researchers as pseudoturbulence. Downstream of the reaction, far away from the disturbances caused by the buoyant bubbles, the velocity fluctuations dampen out and the flow relaminarizes.
Takotsubo cardiomyopathy in a jeweler following a hold-up: forensic considerations.
Savall, Frederic; Dedouit, Fabrice; Telmon, Norbert; RougÕ, Daniel
The authors present a case of takotsubo cardiomyopathy (TTC) following physical assault. In France, public prosecutor orders a medicolegal assessment after an assault for all living victims. Medicolegal assessment aims to establish a causal relation between an aggression and the injury sustained. An 80-year-old jeweler was the victim of assault, restraint and confinement during the hold-up of his jewelry store. After the event, he experienced constrictive chest pain with a sensation of oppression. Transthoracic echography showed apical and middle wall akinesis with apical ballooning pattern. In this case, the experts reasonably accepted that there was a direct, certain, and exclusive causal relation between the aggression and the cardiomyopathy. Forensic specialists should be aware of TTC because it is a frequent complication of stress situations and its incidence in forensic cases is probably underestimated. PMID:23981192
Sonoluminescence: How Bubbles Turn Sound into Light
S. J. Putterman; K. R. Weninger
Sonoluminescence, the transduction of sound into light, is a phenom- enon that pushes fluid mechanics beyond its limit. An initial state with long wave- length and low Mach number, such as is realized for a gas bubble driven by an audible sound field, spontaneously focuses the energy density so as to generate supersonic motion and a different phase of matter,
Previous studies have established that the waste level of Hanford tanks responds to barometric pressure changes, the compressibility of retained bubbles accounts for the level changes, and the volume of retained gas can be determined from the measured waste level and barometric p...
Formation and X-ray emission from hot bubbles in planetary nebulae - I. Hot bubble formation
NASA Astrophysics Data System (ADS)
ToalÃ, J. A.; Arthur, S. J.
We carry out high-resolution two-dimensional radiation-hydrodynamic numerical simulations to study the formation and evolution of hot bubbles inside planetary nebulae. We take into account the evolution of the stellar parameters, wind velocity and mass-loss rate from the final thermal pulses during the asymptotic giant branch (AGB) through to the post-AGB stage for a range of initial stellar masses. The instabilities that form at the interface between the hot bubble and the swept-up AGB wind shell lead to hydrodynamical interactions, photoevaporation flows and opacity variations. We explore the effects of hydrodynamical mixing combined with thermal conduction at this interface on the dynamics, photoionization, and emissivity of our models. We find that even models without thermal conduction mix significant amounts of mass into the hot bubble. When thermal conduction is not included, hot gas can leak through the gaps between clumps and filaments in the broken swept-up AGB shell and this depressurises the bubble. The inclusion of thermal conduction evaporates and heats material from the clumpy shell, which expands to seal the gaps, preventing a loss in bubble pressure. The dynamics of bubbles without conduction is dominated by the thermal pressure of the thick photoionized shell, while for bubbles with thermal conduction it is dominated by the hot, shocked wind.
Anshuman Roy; Marcos Borrell; John Felts; Gary Leal; Amir Hirsa
When two drops or bubbles are brought into close proximity to each other, the thin film of the fluid between them drains as they are squeezed together. If the film becomes thin enough that intermolecular forces of attraction overwhelm capillary forces, the drops\\/bubbles coalesce and the time it takes for this to happen, starting from the point of apparent contact
Evaporation, Boiling and Bubbles
ERIC Educational Resources Information Center
Goodwin, Alan
Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The
ERIC Educational Resources Information Center
Korenic, Eileen
Describes a series of activities and demonstrations involving the science of soap bubbles. Starts with a recipe for bubble solution and gives instructions for several activities on topics such as density, interference colors, optics, static electricity, and galaxy formation. Contains some background information to help explain some of the effects.
Methane bubbling: from speculation to quantification
NASA Astrophysics Data System (ADS)
Grinham, A. R.; Dunbabin, M.; Yuan, Z.
Rates of methane bubbling (ebullition) represent a notoriously difficult emission pathway to quantify with highly variable spatial and temporal changes. However, the importance of bubbling fluxes in terms of total emissions is increasingly recognised from a number of different globally relevant natural systems including lakes, reservoirs and wetlands. This represents a critical challenge to current survey efforts to quantify greenhouse gas emissions and reduce the uncertainty associated with bubbling fluxes. A number of different methods have been proposed to overcome this challenge including bubble traps, floating chambers, echo sounders, laser spectrography and camera systems. Each method has relative merits and deficiencies with all trading-off the ability to directly quantify methane and provide spatial and temporal coverage. Here we present a novel method that allows direct measurement of methane bubble concentration as well as the ability to persistently monitor a wide spatial area. Central to the monitoring system is an Autonomous Surface Vessel (ASV) and an Optical Methane Detector (OMD). The ASV is equipped with solar panels and uses electric motors for propulsion to allow persistent environmental monitoring. The OMD has a path length of 1.3 m and 7 Hz sampling so a typical mission of 3 hours at 1 m s-1 covers an area in excess of 10 000 m2 and over 65 000 data points. The system was assessed on four sub-tropical freshwater reservoirs of varying surface area (0.5 to 100 km2), age (2 to 65 y) and catchment land use (40 to 90% natural vegetation cover). Each reservoir had unique challenges in terms of navigation and field conditions to test feasibility of this method. Deployment length varied from a single day to over 4 months to test method durability. In addition to ASV bubble surveys, floating static chambers were deployed to determine diffusive fluxes. Localised instantaneous bubble flux rates within a single reservoir ranged over three orders of magnitude from 500 to 100 000 mg m-2 d-1 depending on time of day and water depth. Average storage bubble flux rates between reservoirs varied by two orders of magnitude from 1 200 to 15 000 mg m-2 d-1, with the primary driver likely to be catchment forest cover. The relative contribution of bubbling to total fluxes varied from 10% to more than 90% depending on the reservoir and time of sampling. This method was consistently shown to greatly improve the spatial mapping and quantification of methane bubbling rates from reservoir surfaces and reduces the uncertainty associated with the determining the relative contribution of bubbling to total flux.
NASA Astrophysics Data System (ADS)
Yang, Rui-zhi; Aharonian, Felix; Crocker, Roland
We analyze 60 months of all-sky data from the Fermi-LAT. The Fermi bubble structures discovered previously are clearly revealed by our analysis. With more data, hence better statistics, we can now divide each bubble into constant longitude slices to investigate their gross ?-ray spectral morphology. While the detailed spectral behavior of each slice derived in our analysis is somewhat dependent on the assumed background model, we find, robustly, a relative deficit in the flux at low energies (i.e., hardening) toward the top of the south bubble. In neither bubble does the spectrum soften with longitude. The morphology of the Fermi bubbles is also revealed to be energy-dependent: at high energies they are more extended. We conclude from the gamma-ray spectrum at high latitudes that a low energy break in the parent cosmic ray population is required in both leptonic and hadronic models. We briefly discuss possible leptonic and hadronic interpretations of this phenomenology.
Heat transfer investigations in a slurry bubble column: Quarterly report of the period April--June 1988
S. C. Saxena; R. Vadivel; A. K. Verma
Detailed measurements of gas holdup in the small 10.8 cm diameter column have been completed for the two-phase air-water system. Experiments have been conducted in the semi-batch mode as well as in the continuous mode as a function of air velocity. Experiments are done to see the influence, if any, of the 19 mm diameter axial probe in the column
Anomalous capillary pressure, stress, and stability of solids-coated bubbles
Kam, S.I.; Rossen, W.R. [Univ. of Texas, Austin, TX (United States). Dept. of Petroleum and Geosystems Engineering] [Univ. of Texas, Austin, TX (United States). Dept. of Petroleum and Geosystems Engineering
Concern about gas discharges from waste tanks at the Hanford nuclear reservation has led to the study of the mechanisms by which gas is trapped in and then episodically released from these tanks. A two-dimensional theoretical model for solids-coated, or armored, bubbles shows how the armor can support a liquid-vapor interface of reduced or reversed curvature between the particles, giving the bubble zero or even negative capillary pressure. The inward capillary force pulling the particles into the center of the bubble are balanced by large contact forces between the particles in the armor. Thus the bubble is stabilized against dissolution of gas into surrounding liquid, which otherwise would rapidly collapse the bubble. The stresses between particles in such cases are large and could drive sintering of the particles into a rigid framework. Earlier work on solids-coated bubbles assumed that solids can freely enter or leave the bubble surface as the bubble shrinks or expands. In such a case, armored bubbles would not be stable to gas dissolution into surrounding liquid. A new free-energy analysis, however, suggests that a shrunken bubble would not spontaneously expel a solid particle from its armor to relieve stress and allow the bubble to shrink further. Implications and limitations of the theory are discussed.
Bubbles, Bubbles: Integrated Investigations with Floating Spheres
ERIC Educational Resources Information Center
Reeder, Stacy
In this article, the author describes integrated science and mathematics activities developed for fourth-grade students to explore and investigate three-dimensional geometric shapes, Bernoulli's principle, estimation, and art with and through bubbles. Students were engaged in thinking and reflection on the questions their teachers asked and were
A large bubble around the Crab Nebula
NASA Technical Reports Server (NTRS)
Romani, Roger W.; Reach, William T.; Koo, Bon Chul; Heiles, Carl
IRAS and 21 cm observations of the interstellar medium around the Crab nebula show evidence of a large bubble surrounded by a partial shell. If located at the canonical 2 kpc distance of the Crab pulsar, the shell is estimated to have a radius of about 90 pc and to contain about 50,000 solar masses of swept-up gas. The way in which interior conditions of this bubble can have important implications for observations of the Crab are described, and the fashion in which presupernova evolution of the pulsar progenitor has affected its local environment is described.
Bubble core field modification by residual electrons inside the bubble
Wu Haicheng [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Center for Applied Physics and Technology, Peking University, Beijing 100084 (China); Xie Baisong; Zhao Xueyan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Zhang Shan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Department of Mathematics and Physics, Shijiazhuang Railway Institute, Shijiazhuang 050043 (China); Hong Xueren [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Liu Mingping [School of Information Engineering, Nanchang University, Nanchang 330031 (China)
Bubble core field modification due to the nondepleted electrons present inside the bubble is investigated theoretically. These residual electrons induce charge and current densities that can induce the bubble core field modification as well as the bubble shape change. It is found that the electrons entering into the bubble move backward at almost light speed and would weaken the transverse bubble fields. This reduces the ratio of longitudinal to transverse radius of the bubble. For the longitudinal bubble field, two effects compensate with each other because of their competition between the enhancement by the shortening of bubble shape and the reduction by the residual electrons. Therefore the longitudinal field is hardly changeable. As a comparison we perform particle-in-cell simulations and it is found that the results from theoretical consideration are consistent with simulation results. Implication of the modification of fields on bubble electron acceleration is also discussed briefly.
Characterization of acoustic droplet vaporization for control of bubble generation under flow conditions.
Kang, Shih-Tsung; Huang, Yi-Luan; Yeh, Chih-Kuang
This study investigated the manipulation of bubbles generated by acoustic droplet vaporization (ADV) under clinically relevant flow conditions. Optical microscopy and high-frequency ultrasound imaging were used to observe bubbles generated by 2-MHz ultrasound pulses at different time points after the onset of ADV. The dependence of the bubble population on droplet concentration, flow velocity, fluid viscosity and acoustic parameters, including acoustic pressure, pulse duration and pulse repetition frequency, was investigated. The results indicated that post-ADV bubble growth spontaneously driven by air permeation markedly affected the bubble population after insonation. The bubbles can grow to a stable equilibrium diameter as great as twice the original diameter in 0.5-1 s, as predicted by the theoretical calculation. The growth trend is independent of flow velocity, but dependent on fluid viscosity and droplet concentration, which directly influence the rate of gas uptake by bubbles and the rate of gas exchange across the wall of the semipermeable tube containing the bubbles and, hence, the gas content of the host medium. Varying the acoustic pressure does not markedly change the formation of bubbles as long as the ADV thresholds of most droplets are reached. Varying pulse duration and pulse repetition frequency markedly reduces the number of bubbles. Lengthening pulse duration favors the production of large bubbles, but reduces the total number of bubbles. Increasing the PRF interestingly provides superior performance in bubble disruption. These results also suggest that an ADV bubble population cannot be assessed simply on the basis of initial droplet size or enhancement of imaging contrast by the bubbles. Determining the optimal acoustic parameters requires careful consideration of their impact on the bubble population produced for different application scenarios. PMID:24433748
Transformation of deep-water methane bubbles into hydrate
Egorov, Alexander V; Rozhkov, Aleksey N
The paper is dedicated to the mechanics of the methane bubbles in the gas hydrate stability zone of the basin. Transformation of deep-water methane bubbles into solid hydrate was investigated in Lake Baikal in situ. Released from the bottom methane bubbles were caught by different traps with transparent walls. It was observed that when bubbles entered into internal space of the trap, the bubbles could be transformed into two different solid hydrate structures depending on ambient conditions. The first structure is hydrate granular matter consisted of solid fragments with sizes of order of 1 mm. The second structure is high porous solid foam consisted of solid bubbles with sizes of order of 5 mm. The formed granular matter did not change during trap lifting up to top border of gas hydrate stability zone, whereas free methane intensively released from solid foam sample during it lifting. It was concluded that the decrease of the depth of bubble sampling and the decrease of the bubble flux rate assist to formati...
Abt, Helmut A., E-mail: firstname.lastname@example.com [Kitt Peak National Observatory, P.O. Box 26732, Tucson, AZ 85726-6732 (United States)
The Local Interstellar Bubble is an irregular region from 50 to 150 pc from the Sun in which the interstellar gas density is 10{sup -2}-10{sup -3} of that outside the bubble and the interstellar temperature is 10{sup 6} K. Evidently most of the gas was swept out by one or more supernovae. I explored the stellar contents and ages of the region from visual double stars, spectroscopic doubles, single stars, open clusters, emission regions, X-ray stars, planetary nebulae, and pulsars. The bubble has three sub-regions. The region toward the galactic center has stars as early as O9.5 V and with ages of 2-4 M yr. It also has a pulsar (PSRJ1856-3754) with a spin-down age of 3.76 Myr. That pulsar is likely to be the remnant of the supernova that drove away most of the gas. The central lobe has stars as early as B7 V and therefore an age of about 160 Myr or less. The Pleiades lobe has stars as early as B3 and therefore an age of about 50 Myr. There are no obvious pulsars that resulted from the supernovae that cleared out those areas. As found previously by Welsh and Lallement, the bubble has five B stars along its perimeter that show high-temperature ions of O VI and C II along their lines of sight, confirming its high interstellar temperature.
Aerator Combined With Bubble Remover
NASA Technical Reports Server (NTRS)
Dreschel, Thomas W.
System produces bubble-free oxygen-saturated water. Bubble remover consists of outer solid-walled tube and inner hydrophobic, porous tube. Air bubbles pass from water in outer tube into inner tube, where sucked away. Developed for long-term aquaculture projects in space. Also applicable to terrestrial equipment in which entrained bubbles dry membranes or give rise to cavitation in pumps.
Rotating bubble membrane radiator
Webb, Brent J. (West Richland, WA); Coomes, Edmund P. (West Richland, WA)
A heat radiator useful for expelling waste heat from a power generating system aboard a space vehicle is disclosed. Liquid to be cooled is passed to the interior of a rotating bubble membrane radiator, where it is sprayed into the interior of the bubble. Liquid impacting upon the interior surface of the bubble is cooled and the heat radiated from the outer surface of the membrane. Cooled liquid is collected by the action of centrifical force about the equator of the rotating membrane and returned to the power system. Details regarding a complete space power system employing the radiator are given.
Using an Ultrasonic Instrument to Size Extravascular Bubbles
NASA Technical Reports Server (NTRS)
Magari, Patrick J.; Kline-Schroder, J.; Kenton, Marc A.
In an ongoing development project, microscopic bubbles in extravascular tissue in a human body will be detected by use of an enhanced version of the apparatus described in Ultrasonic Bubble- Sizing Instrument (MSC-22980), NASA Tech Briefs, Vol. 24, No. 10 (October 2000), page 62. To recapitulate: The physical basis of the instrument is the use of ultrasound to excite and measure the resonant behavior (oscillatory expansion and contraction) of bubbles. The resonant behavior is a function of the bubble diameter; the instrument exploits the diameter dependence of the resonance frequency and the general nonlinearity of the ultrasonic response of bubbles to detect bubbles and potentially measure their diameters. In the cited prior article, the application given most prominent mention was the measurement of gaseous emboli (essentially, gas bubbles in blood vessels) that cause decompression sickness and complications associated with cardiopulmonary surgery. According to the present proposal, the instrument capabilities would be extended to measure extravascular bubbles with diameters in the approximate range of 1 to 30 m. The proposed use of the instrument could contribute further to the understanding and prevention of decompression sickness: There is evidence that suggests that prebreathing oxygen greatly reduces the risk of decompression sickness by reducing the number of microscopic extravascular bubbles. By using the ultrasonic bubble-sizing instrument to detect and/or measure the sizes of such bubbles, it might be possible to predict the risk of decompression sickness. The instrument also has potential as a tool to guide the oxygen-prebreathing schedules of astronauts; high-altitude aviators; individuals who undertake high-altitude, low-opening (HALO) parachute jumps; and others at risk of decompression sickness. For example, an individual at serious risk of decompression sickness because of high concentrations of extravascular microscopic bubbles could be given a warning to continue to prebreathe oxygen until it was safe to decompress.
Mechanisms of stability of armored bubbles: FY 1996 Final Report
Rossen, W.R.; Kam, S.I.
Theoretical and experimental studies examine how a coating, or {open_quotes}armor,{close_quotes} of partially wetted solid particles can stabilize tiny bubbles against diffusion of gas into the surrounding liquid, in spite of the high capillary pressures normally associated with such bubbles. Experiments with polymethylmethacrylate (PNMA) beads and carbonated water demonstrate that armored bubbles can persist for weeks in liquid unsaturated with respect to the gas in the bubbles. This question is of concern regarding gas discharges from waste tanks at the Hanford reservation. The stresses on the solid-solid contacts between particles in such cases is large and could drive sintering of the particles into a rigid framework. Stability analysis suggests that a slightly shrunken bubble would not expel a solid particle from its armor to relieve stress and allow the bubble to shrink further. Expulsion of particles from more stressed bubbles at zero capillary pressure is energetically favored in some cases. It is not clear, however, whether this expulsion would proceed spontaneously from a small perturbation or require a large initial disturbance of the bubble. In some cases, it appears that a bubble would expel some particles and shrink, but the bubble would approach a final, stable size rather than disappear completely. This simplified analysis leaves out several factors. For instance, only one perturbation toward expelling a solid from the armor is considered; perhaps other perturbations would be more energetically favored than that tested. Other considerations (particle deformation, surface roughness, contact-angle hysteresis, and adhesion or physical bonding between adjacent particles) would make expelling solids more difficult than indicated by this theoretical study.
Acoustofluidic control of bubble size in microfluidic flow-focusing configuration.
Chong, Zhuang Zhi; Tor, Shu Beng; Loh, Ngiap Hiang; Wong, Teck Neng; GaþÃn-Calvo, Alfonso M; Tan, Say Hwa; Nguyen, Nam-Trung
This paper reports a method to control the bubble size generated in a microfluidic flow-focusing configuration. With an ultrasonic transducer, we induce acoustic streaming using a forward moving, oscillating gas-liquid interface. The induced streaming substantially affects the formation process of gas bubbles. The oscillating interface acts as a pump that increases the gas flow rate significantly and forms a larger bubble. This method is applicable to a wide range of gas pressure from 30 to 90 kPa and flow rate from 380 to 2700 ?L h(-1). The bubble size can be tuned repeatedly with the response time on the order of seconds. We believe that this method will enhance the capability of a microfluidic bubble generator to produce a tunable bubble size. PMID:25510843
Bubble counter based on photoelectric technique for leakage detection of cryogenic valves
Tao Jin; Bin Xu; Ke Tang; Jian-ping Hong
In order to overcome the inconvenience of manual bubble counting, a bubble counter based on photoelectric technique aiming\\u000a for automatically detecting and measuring minute gas leakage of cryogenic valves is proposed. Experiments have been conducted\\u000a on a self-built apparatus, testing the performance with different gas inlet strategies (bottom gas-inlet strategy and side\\u000a gas-inlet strategy) and the influence of gas pipe
Comparison of two phase liquid holdup and pressure drop correlations across flow regime boundaries for horizontal and inclined pipes
Arya, A.; Gould, T.L.
During the last decade the interest in two-phase flow through horizontal and inclined pipes has increased considerably,. Design engineers are primarily concerned with the calculation of pressure drop in two-phase lines and prediction of liquid holdup (in-situ liquid volume fraction), in order to size flow lines and calculate slug catcher size. These calculations are also important for the design of surface facilities such as pumps, compressors and separators. The correlations tested in this study first predict the flow pattern in the pipeline at the specified physical conditions with the help of a flow pattern map. After determining the flow pattern, the corresponding holdup and friction factor correlations are used to calculate pressure drop. 7 refs.
A Generalized Finite Source Calibration Factor: A Natural Improvement to the Finite Source Correction Factor for Uranium Holdup Measurements
Gunn, C.A.; Oberer, R.B.; chiang, L.G.; Ceo, R.N.
This paper proposes refinements to the finite source correction factor used in holdup measurements. Specifically it focuses on a more general method to estimate the average detector response for a finite source. This proposed method for the average detector response is based directly on the Generalized Geometry Holdup (GGH) assay method. First, the finite source correction factor as originally proposed is reviewed in this paper. Following this review the GGH assay method is described. Lastly, a new finite area calibration factor based on GGH is then proposed for finite point and line sources. As an alternative to the direct use of the finite arca calibration factor, finite source correction factors are also derived from this calibration factor. This new correction factor can be used in a manner similar to the finite source correction factor as currently implemented.
Standard test method for nondestructive assay of special nuclear material holdup using Gamma-Ray spectroscopic methods
American Society for Testing and Materials. Philadelphia
1.1 This test method describes gamma-ray methods used to nondestructively measure the quantity of 235U, or 239Pu remaining as holdup in nuclear facilities. Holdup occurs in all facilities where nuclear material is processed, in process equipment, in exhaust ventilation systems and in building walls and floors. 1.2 This test method includes information useful for management, planning, selection of equipment, consideration of interferences, measurement program definition, and the utilization of resources (1, 2, 3, 4). 1.3 The measurement of nuclear material hold up in process equipment requires a scientific knowledge of radiation sources and detectors, transmission of radiation, calibration, facility operations and error analysis. It is subject to the constraints of the facility, management, budget, and schedule; plus health and safety requirements; as well as the laws of physics. The measurement process includes defining measurement uncertainties and is sensitive to the form and distribution of the material...
Development of a neural network model for the prediction of liquid holdup in two-phase horizontal flow
Shippen, Mack Edward
96 116 LIST OF FIGURES FIGURE Page I Horizontal flow patterns 2 Schematic of multilayer perceptron neural network . . . . 17 3 Illustration of neural network overlearning. 20 4 Illustration of discrete neural network. 35 5 Illustration... Occurrence of flow patterns in experimental data 26 4 Liquid holdup range in experimental data 26 5 Scaling factors, weights and thresholds ? discrete neural network, . . . . . . . . . . 35 6 Scaling factors, weights and thresholds ? dimensionless neural...
Comparison of Two Phase Liquid Holdup and Pressure Drop Correlations Across Flow Regime Boundaries for Horizontal and Inclined Pipes
Atul Arya; Thomas Gould
During the last decade the interest in two-phase flow through horizontal and inclined pipes has increased considerably,. Design engineers are primarily concerned with the calculation of pressure drop in two-phase lines and prediction of liquid holdup (in-situ liquid volume fraction), in order to size flow lines and calculate slug catcher size. These calculations are also important for the design of
NASA Technical Reports Server (NTRS)
These NASA Hubble Space Telescope snapshots reveal dramatic activities within the core of the galaxy NGC 3079, where a lumpy bubble of hot gas is rising from a cauldron of glowing matter. The picture at left shows the bubble in the center of the galaxy's disk. The structure is more than 3,000 light-years wide and rises 3,500 light-years above the galaxy's disk. The smaller photo at right is a close-up view of the bubble. Astronomers suspect that the bubble is being blown by 'winds' (high-speed streams of particles) released during a burst of star formation. Gaseous filaments at the top of the bubble are whirling around in a vortex and are being expelled into space. Eventually, this gas will rain down upon the galaxy's disk where it may collide with gas clouds, compress them, and form a new generation of stars. The two white dots just above the bubble are probably stars in the galaxy. The close-up reveals that the bubble's surface is lumpy, consisting of four columns of gaseous filaments that tower above the galaxy's disk. The filaments disperse at a height of 2,000 light-years. Each filament is about 75 light-years wide. Velocity measurements taken by the Canada-France-Hawaii Telescope in Hawaii show that the gaseous filaments are ascending at more than 4 million miles an hour (6 million kilometers an hour). According to theoretical models, the bubble formed when ongoing winds from hot stars mixed with small bubbles of very hot gas from supernova explosions. Observations of the core's structure by radio telescopes indicate that those processes are still active. The models suggest that this outflow began about a million years ago. They occur about every 10 million years. Eventually, the hot stars will die, and the bubble's energy source will fade away. Astronomers have seen evidence of previous outbursts from radio and X-ray observations. Those studies show rings of dust and gas and long plumes of material, all of which are larger than the bubble. NGC 3079 is 50 million light-years from Earth in the constellation Ursa Major. The colors in this image accentuate important details in the bubble. Glowing gas is red and starlight is blue/green. Hubble's Wide Field and Planetary Camera 2 snapped this picture in 1998. The results appear in the July 1, 2001 issue of the Astrophysical Journal. Credits: NASA, Gerald Cecil (University of North Carolina), Sylvain Veilleux (University of Maryland), Joss Bland-Hawthorn (Anglo-Australian Observatory), and Alex Filippenko (University of California at Berkeley).
ERIC Educational Resources Information Center
Saunderson, Megan
Describes a unit on detergents and bubbles that establishes an interest in the properties of materials and focuses on active learning involving both hands- and minds-on learning rather than passive learning. (ASK)
Bubble impacts with microcantilevers.
NASA Astrophysics Data System (ADS)
Stegmeir, Matthew; Longmire, Ellen; Ali, Mubassar; Mantell, Susan
In the current study, we investigate bubbles in laminar channel flows impacting microcantilever obstacles. Static and resonating cantilevers instrumented with integrated strain gages are mounted perpendicular to the mean flow in a vertically-oriented channel with thickness 2mm, span 10mm, and length 585 mm. Steady, fully-developed upward flows with channel Reynolds numbers based on mean fluid velocity and hydraulic diameter of 0-2500 are considered. Bubbles of diameter 200-1000?m are introduced upstream of the test section, and impacts are observed using a microscope equipped with a high frame rate camera. Observations are made along the length of cantilevers backlit with white light. Strain gage signals are monitored and correlated to impact events. The effect of obstacles on bubble motion and deformation as well as the effect of bubble impacts on the cantilever will be discussed. The flow studies are part of a larger research program examining reliability and performance of vibrating microbeams.
ERIC Educational Resources Information Center
Lee, Albert W. M.; Wong, A.; Lee, H. W.; Lee, H. Y.; Zhou, Ning-Huai
Describes a laboratory experiment in which common chemical gases are trapped inside soap bubbles. Examines the physical and chemical properties of the gases such as relative density and combustion. (Author/MM)
Valentin Puente; Cruz Izu; Ramµn Beivide; JosÕ A. Gregorio; Fernando Vallejo; J. M. Prellezo
The design of a new adaptive virtual cut-through router for torus networks is presented in this paper. With much lower VLSI costs than adaptive wormhole routers, the adaptive Bubble router is even faster than deterministic wormhole routers based on virtual channels. This has been achieved by combining a low-cost deadlock avoidance mechanism for virtual cut-through networks, called Bubble flow control,
Observations of the collapses and rebounds of millimeter-sized lithotripsy bubbles
Kreider, Wayne; Crum, Lawrence A.; Bailey, Michael R.; Sapozhnikov, Oleg A.
Bubbles excited by lithotripter shock waves undergo a prolonged growth followed by an inertial collapse and rebounds. In addition to the relevance for clinical lithotripsy treatments, such bubbles can be used to study the mechanics of inertial collapses. In particular, both phase change and diffusion among vapor and noncondensable gas molecules inside the bubble are known to alter the collapse dynamics of individual bubbles. Accordingly, the role of heat and mass transport during inertial collapses is explored by experimentally observing the collapses and rebounds of lithotripsy bubbles for water temperatures ranging from 20 to 60 ¯C and dissolved gas concentrations from 10 to 85% of saturation. Bubble responses were characterized through high-speed photography and acoustic measurements that identified the timing of individual bubble collapses. Maximum bubble diameters before and after collapse were estimated and the corresponding ratio of volumes was used to estimate the fraction of energy retained by the bubble through collapse. The rebounds demonstrated statistically significant dependencies on both dissolved gas concentration and temperature. In many observations, liquid jets indicating asymmetric bubble collapses were visible. Bubble rebounds were sensitive to these asymmetries primarily for water conditions corresponding to the most dissipative collapses. PMID:22088027
Clustering in Bubble Suspensions
NASA Astrophysics Data System (ADS)
Zenit, Roberto
A monidisperse bubble suspension is studied experimentally for the limit in which the Weber number is small and the Reynolds number is large. For this regime the suspension can be modeled using potential flow theory to describe the dynamics of the interstitial fluid. Complete theoretical descriptions have been composed (Spelt and Sangani, 1998) to model the behavior of these suspensions. Bubble clustering is a natural instability that arises from the potential flow considerations, in which bubbles tend to align in horizontal rafts as they move upwards. The appearance of bubble clusters was recently corroborated experimentally by Zenit et al. (2000), who found that although clusters did appear, their strength was not as strong as the predictions. Experiments involving gravity driven shear flows are used to explain the nature of the clustering observed in these type of flows. Balances of the bubble phase pressure (in terms of a calculated diffusion coefficient) and the Maxwell pressure (from the potential flow description) are presented to predict the stability of the bubble suspension. The predictions are compared with experimental results.
A polydisperse two-fluid model for surf zone bubble simulation
NASA Astrophysics Data System (ADS)
Ma, Gangfeng; Shi, Fengyan; Kirby, James T.
Wave breaking in the surf zone entrains large volumes of air bubbles into the water column, forming a two-phase bubbly flow field. Numerical study of bubbly flow is largely restricted by the lack of robust and comprehensive bubble entrainment models. In this paper, we propose a new model that connects bubble entrainment with turbulent dissipation rate at the air-water interface. The entrainment model as well as a polydisperse two-fluid model are incorporated into a 3-D volume of fluid code TRUCHAS. The bubbly flow model is first tested against laboratory experimental data for an oscillatory bubble plume. The calculated time-averaged liquid velocities and their fluctuations agree well with measurements, indicating that the model correctly reproduces dynamic interactions between the liquid phase and the continuum representation of the gas phase. Then, it is employed to study the bubbly flow under a laboratory surf zone breaking wave. Through the comparisons with experimental data, it is demonstrated that the model describes bubble entrainment and void fraction evolution reasonably well. The exponential decay of void fraction observed in the laboratory experiments is captured by the model. The kinematics of bubble plume as well as the vertical evolution of bubble size spectrum at any depth are investigated. Studies of bubble effects on liquid phase turbulence show that the presence of bubbles could suppress a large amount of turbulence under breaking waves.
Single Bubble SonoLuminescence of Particles model
Mahamadou Adama Maiga
The Single Bubble SonoLuminescence is a phenomenon where the vapor bubble trapped in a liquid collapse by emitting of a light. It is very known that the temperature inside the bubble depends on the radius, during the collapse, the temperature can reach thousands of Kelvins and that the light would be emitted by radiation of the ionized gas inside the bubble. So, studies show that in certain cases neither an imploding shock nor a plasma has been observed and the temperature is not high enough to explain the spectrum observed. The Single Bubble SonoLuminescence remains a subject of study. For this study we consider the bubble as a box where the free particles (particularly electrons) stemming from the molecules dissociation, are are trapped and confined within the bubble. The confinement allows the particles to acquire some energy during the collapse which they lose in the form of light and also to be considered to bind to the bubble as an electron is bound to the nucleus in an atom. So, with regard to the bubble the energy of the particles can be considered to quantify, and with the quantum theory, by putting some hypotheses, their energy is determined well. The energy is physically acceptable that if the bubble is spherical. This necessary condition of a spherical bubble of the model is observed experimentally in the collapse phase but not in the afterbounce phase of the bubble, explain why the bubble emits of light in the collapse but not in the phase of the afterbounces where she can be smaller, and constitute a validation of the Single Bubble SonoLuminescence of particles model. For the application of the Single Bubble SonoLuminescence of particles model we consider a electron free particle of mass . We note that the interval of time between and energy (who can be considered as the duration when the bubble emits some light) is of the order of picoseconds, the same order that the shortest pulses observed experimentally.
Optimization of bubble column performance for nanoparticle collection.
Cadavid-Rodriguez, M C; Charvet, A; Bemer, D; Thomas, D
Fibrous media embody the most effective and widely used method of separating ultrafine particles from a carrier fluid. The main problem associated with them is filter clogging, which induces an increasingly marked pressure drop with time and thus imposes regular media cleaning or replacement. This context has prompted the idea of investigating bubble columns, which operate at constant pressure drop, as alternatives to fibrous filters. This study examines the influence of different operating conditions, such as liquid height, air flow rate, bubble size and presence of granular beds on ultrafine particle collection. Experimental results show that bubble columns are characterised by high collection efficiency, when they feature a large liquid height and small diameter bubbling orifices, while their efficiencies remain lower than those of fibrous filters. Gas velocity does not greatly influence collection efficiency, but the inclusion of a granular bed, composed of beads, increases the bubble residence time in the column, thereby increasing the column collection efficiency. PMID:24584069
Interaction of two oscillating sonoluminescence bubbles in sulfuric acid.
Sadighi-Bonabi, Rasoul; Rezaee, Nastaran; Ebrahimi, Homa; Mirheydari, Mona
The mutual interaction of two oscillating gas bubbles in different concentrations of sulfuric acid is numerically investigated. A nonlinear oscillation for spherical symmetric bubbles with equilibrium radii smaller than 10 ?m at a frequency of 37 kHz in a strong driving acoustical field P(a)=1.8 bar is assumed. The calculations are based on the investigation of the secondary Bjerknes force with regard to adiabatic model for the bubble interior which appears as repulsion or attraction interaction force. In this work the influence of the various concentrations of sulfuric acid in uncoupled and coupled distances between bubbles has been investigated. It is found that the sign and value of the secondary Bjerknes force depend on the sulfuric acid viscosity and its amount would be decreased by liquid viscosity enhancement. The results show that big change in the parameters of produced bubbles occurs in the sulfuric acid with concentrations from 65% to 85%. PMID:20866734
Bubble Eliminator Based on Centrifugal Flow
NASA Technical Reports Server (NTRS)
Gonda, Steve R.; Tsao, Yow-Min D.; Lee, Wenshan
The fluid bubble eliminator (FBE) is a device that removes gas bubbles from a flowing liquid. The FBE contains no moving parts and does not require any power input beyond that needed to pump the liquid. In the FBE, the buoyant force for separating the gas from the liquid is provided by a radial pressure gradient associated with a centrifugal flow of the liquid and any entrained bubbles. A device based on a similar principle is described in Centrifugal Adsorption Cartridge System (MSC- 22863), which appears on page 48 of this issue. The FBE was originally intended for use in filtering bubbles out of a liquid flowing relatively slowly in a bioreactor system in microgravity. Versions that operate in normal Earth gravitation at greater flow speeds may also be feasible. The FBE (see figure) is constructed as a cartridge that includes two concentric cylinders with flanges at the ends. The outer cylinder is an impermeable housing; the inner cylinder comprises a gas-permeable, liquid-impermeable membrane covering a perforated inner tube. Multiple spiral disks that collectively constitute a spiral ramp are mounted in the space between the inner and outer cylinders. The liquid enters the FBE through an end flange, flows in the annular space between the cylinders, and leaves through the opposite end flange. The spiral disks channel the liquid into a spiral flow, the circumferential component of which gives rise to the desired centrifugal effect. The resulting radial pressure gradient forces the bubbles radially inward; that is, toward the inner cylinder. At the inner cylinder, the gas-permeable, liquid-impermeable membrane allows the bubbles to enter the perforated inner tube while keeping the liquid in the space between the inner and outer cylinders. The gas thus collected can be vented via an endflange connection to the inner tube. The centripetal acceleration (and thus the radial pressure gradient) is approximately proportional to the square of the flow speed and approximately inversely proportional to an effective radius of the annular space. For a given FBE geometry, one could increase the maximum rate at which gas could be removed by increasing the rate of flow to obtain more centripetal acceleration. In experiments and calculations oriented toward the original microgravitational application, centripetal accelerations between 0.001 and 0.012 g [where g normal Earth gravitation (.9.8 m/s2)] were considered. For operation in normal Earth gravitation, it would likely be necessary to choose the FBE geometry and the rate of flow to obtain centripetal acceleration comparable to or greater than g.
Time correlated single photon Mie scattering from a sonoluminescing bubble K. R. Weninger,1
Evans, Paul G.
The acoustically driven pulsations of a gas bubble in wa- ter can be so nonlinear as to generate broad band scattering measurements may be due to light scattered by the outgoing acoustic ``shock'' wave around those gleaned from the data. The Mie scattering experiments were conducted on gas bubbles levitated
Bubble Point Measurements with Liquid Methane of a Screen Channel Capillary Liquid Acquisition Device
NASA Technical Reports Server (NTRS)
Jurns, John M.; McQuillen, John B.; Gaby, Joseph D., Jr.; Sinacore, Steven A., Jr.
Liquid acquisition devices (LADs) can be utilized within a propellant tank in space to deliver single-phase liquid to the engine in low gravity. One type of liquid acquisition device is a screened gallery whereby a fine mesh screen acts as a 'bubble filter' and prevents the gas bubbles from passing through until a crucial pressure differential condition across the screen, called the bubble point, is reached. This paper presents data for LAD bubble point data in liquid methane (LCH4) for stainless steel Dutch twill screens with mesh sizes of 325 by 2300. These tests represent the first known nonproprietary effort to collect bubble point data for LCH4.
BEM-based numerical study of three-dimensional compressible bubble dynamics in stokes flow
NASA Astrophysics Data System (ADS)
Abramova, O. A.; Akhatov, I. Sh.; Gumerov, N. A.; Itkulova, Yu. A.
The dynamics of compressible gas bubbles in a viscous shear flow and an acoustic field at low Reynolds numbers is studied. The numerical approach is based on the boundary element method (BEM), which is effective as applied to the three-dimensional simulation of bubble deformation. However, the application of the conventional BEM to compressible bubble dynamics faces difficulties caused by the degeneration of the resulting algebraic system. Additional relations based on the Lorentz reciprocity principle are used to cope with this problem. Test computations of the dynamics of a single bubble and bubble clusters in acoustic fields and shear flows are presented.
Mechanics of Bubbles in Sludges and Slurries Modeling Studies of Particulate Materials
Phillip A. Gauglitz; Guillermo Terrones; Susan J. Muller; Morton M. Denn; William R. Rossen
The Hanford Site has 177 underground waste storage tanks that are known to retain and release bubbles composed of flammable gases. Characterizing and understanding the behavior of these bubbles is important for the safety issues associated with the flammable gases for both ongoing waste storage and future waste-retrieval operations. The retained bubbles are known to respond to small barometric pressure changes, though in a complex manner with unusual hysteresis occurring in some tanks in the relationship between bubble volume and pressure, or V-P hysteresis. With careful analysis, information on the volume of retained gas and the interactions of the waste and the bubbles can be determined.
Statistical equilibrium of bubble oscillations in dilute bubbly flows
Colonius, Tim; Hagmeijer, Rob; Ando, Keita; Brennen, Christopher E.
The problem of predicting the moments of the distribution of bubble radius in bubbly flows is considered. The particular case where bubble oscillations occur due to a rapid (impulsive or step change) change in pressure is analyzed, and it is mathematically shown that in this case, inviscid bubble oscillations reach a stationary statistical equilibrium, whereby phase cancellations among bubbles with different sizes lead to time-invariant values of the statistics. It is also shown that at statistical equilibrium, moments of the bubble radius may be computed using the period-averaged bubble radius in place of the instantaneous one. For sufficiently broad distributions of bubble equilibrium (or initial) radius, it is demonstrated that bubble statistics reach equilibrium on a time scale that is fast compared to physical damping of bubble oscillations due to viscosity, heat transfer, and liquid compressibility. The period-averaged bubble radius may then be used to predict the slow changes in the moments caused by the damping. A benefit is that period averaging gives a much smoother integrand, and accurate statistics can be obtained by tracking as few as five bubbles from the broad distribution. The period-averaged formula may therefore prove useful in reducing computational effort in models of dilute bubbly flow wherein bubbles are forced by shock waves or other rapid pressure changes, for which, at present, the strong effects caused by a distribution in bubble size can only be accurately predicted by tracking thousands of bubbles. Some challenges associated with extending the results to more general (nonimpulsive) forcing and strong two-way coupled bubbly flows are briefly discussed. PMID:19547725
Statistical equilibrium of bubble oscillations in dilute bubbly flows.
Colonius, Tim; Hagmeijer, Rob; Ando, Keita; Brennen, Christopher E
The problem of predicting the moments of the distribution of bubble radius in bubbly flows is considered. The particular case where bubble oscillations occur due to a rapid (impulsive or step change) change in pressure is analyzed, and it is mathematically shown that in this case, inviscid bubble oscillations reach a stationary statistical equilibrium, whereby phase cancellations among bubbles with different sizes lead to time-invariant values of the statistics. It is also shown that at statistical equilibrium, moments of the bubble radius may be computed using the period-averaged bubble radius in place of the instantaneous one. For sufficiently broad distributions of bubble equilibrium (or initial) radius, it is demonstrated that bubble statistics reach equilibrium on a time scale that is fast compared to physical damping of bubble oscillations due to viscosity, heat transfer, and liquid compressibility. The period-averaged bubble radius may then be used to predict the slow changes in the moments caused by the damping. A benefit is that period averaging gives a much smoother integrand, and accurate statistics can be obtained by tracking as few as five bubbles from the broad distribution. The period-averaged formula may therefore prove useful in reducing computational effort in models of dilute bubbly flow wherein bubbles are forced by shock waves or other rapid pressure changes, for which, at present, the strong effects caused by a distribution in bubble size can only be accurately predicted by tracking thousands of bubbles. Some challenges associated with extending the results to more general (nonimpulsive) forcing and strong two-way coupled bubbly flows are briefly discussed. PMID:19547725
Bubble Pinch-off at High Pressures
NASA Astrophysics Data System (ADS)
Burton, J. C.; Taborek, P.
Previously we have studied the pinch-off of conventional air bubbles in water [1]. For inviscid fluids, the shrinking of the neck radius of the bubble can be described by a power-law in time with an exponent close to 1/2. As the density of the interior gas is increased, instabilities are expected to occur in the liquid/gas interface [2]. We present high-speed videos and numerical simulations of the pinch-off of high-pressure gaseous bubbles in and exterior inviscid fluid. The density ratio between the exterior fluid and interior gas is D=?ext/?int. In the simple case of small D0.001, the pinch-off is similar to that of a water drop pinching-off in air, while at large D1000, the pinch-off is that of an air bubble in water. By using sulfur hexafluoride as a working gas, we are able to span a wide ranging of density ratios simply by increasing the pressure of the gas. A high-pressure (30 atm) chamber with optical access through sapphire windows was constructed in order to view the pinch-off. The numerical simulations are performed assuming perfectly inviscid fluids using boundary-integral techniques. Instabilities in the interface are seen for intermediate density ratios. Comparisons between experimental and numerical results will be discussed. [1] J.C. Burton, R. Waldrep, and P. Taborek. Phys. Rev. Lett. 94, 184502, (2005). [2] D. Leppinen and J.R. Lister. Phys. Fluids 15, 568, (2003).
An approach to determine the total measurement uncertainty (TMU) associated with Generalized Geometry Holdup (GGH) [1,2,3] measurements was developed and implemented in 2004 and 2005 [4]. This paper describes a condensed version of the TMU calculational model, including recent developments. Recent modifications to the TMU calculation model include a change in the attenuation uncertainty, clarifying the definition of the forward background uncertainty, reducing conservatism in the random uncertainty by selecting either a propagation of counting statistics or the standard deviation of the mean, and considering uncertainty in the width and height as a part of the self attenuation uncertainty. In addition, a detection limit is calculated for point sources using equations derived from summary equations contained in Chapter 20 of MARLAP [5]. The Defense Nuclear Facilities Safety Board (DNFSB) Recommendation 2007-1 to the Secretary of Energy identified a lack of requirements and a lack of standardization for performing measurements across the U.S. Department of Energy (DOE) complex. The DNFSB also recommended that guidance be developed for a consistent application of uncertainty values. As such, the recent modifications to the TMU calculational model described in this paper have not yet been implemented. The Plutonium Finishing Plant (PFP) is continuing to perform uncertainty calculations as per Reference 4. Publication at this time is so that these concepts can be considered in developing a consensus methodology across the complex.
Single Bubble SonoLuminescence of Particles model
Maiga, Mahamadou Adama
The Single Bubble SonoLuminescence is a phenomenon where the vapor bubble trapped in a liquid collapse by emitting of a light. It is very known that the temperature inside the bubble depends on the radius, during the collapse, the temperature can reach thousands of Kelvins and that the light would be emitted by radiation of the ionized gas inside the bubble. So, studies show that in certain cases neither an imploding shock nor a plasma has been observed and the temperature is not high enough to explain the spectrum observed. The Single Bubble SonoLuminescence remains a subject of study. For this study we consider the bubble as a box where the free particles (particularly electrons) stemming from the molecules dissociation, are are trapped and confined within the bubble. The confinement allows the particles to acquire some energy during the collapse which they lose in the form of light and also to be considered to bind to the bubble as an electron is bound to the nucleus in an atom. So, with regard to the bubb...
Cartilage formation in the CELLS 'double bubble' hardware
NASA Technical Reports Server (NTRS)
Duke, P. J.; Arizpe, Jorge; Montufar-Solis, Dina
The CELLS experiment scheduled to be flown on the first International Microgravity Laboratory is designed to study the effect of microgravity on the cartilage formation, by measuring parameters of growth in a differentiating cartilage cell culture. This paper investigates the conditions for this experiment by studying cartilage differentiation in the 'bubble exchange' hardware with the 'double bubble' design in which the bubbles are joined by a flange which also overlays the gasket. Four types of double bubbles (or double gas permeable membranes) were tested: injection-molded bubbles 0.01- and 0.005-in. thick, and compression molded bubbles 0.015- and 0.01-in. thick. It was found that double bubble membranes of 0.005- and 0.010-in. thickness supported cartilage differentiation, while the 0.015-in. bubbles did not. It was also found that nodule count, used in this study as a parameter, is not the best measure of the amount of cartilage differentiation.
Colliding with a crunching bubble
Freivogel, Ben; Freivogel, Ben; Horowitz, Gary T.; Shenker, Stephen
In the context of eternal inflation we discuss the fate of Lambda = 0 bubbles when they collide with Lambda< 0 crunching bubbles. When the Lambda = 0 bubble is supersymmetric, it is not completely destroyed by collisions. If the domain wall separating the bubbles has higher tension than the BPS bound, it is expelled from the Lambda = 0 bubble and does not alter its long time behavior. If the domain wall saturates the BPS bound, then it stays inside the Lambda = 0 bubble and removes a finite fraction of future infinity. In this case, the crunch singularity is hidden behind the horizon of a stable hyperbolic black hole.
Interaction between therapeutic ultrasound propagation and cavitation bubbles
NASA Astrophysics Data System (ADS)
Liebler, Marko; Dreyer, Thomas; Riedlinger, Rainer
In medical applications of high intense focused ultrasound using pressure pulses or continuous wave signals, cavitation is considered to play a significant role for physical and biological effects. To further develop therapeutic applications it is essential to improve the understanding of these cavitation related effects. In this paper a numerical model is presented to simulate the interactions between ultrasonic waves and cavitation bubbles. The FDTD model is based on a two-phase continuum approach for bubbly liquids and combines nonlinear ultrasound propagation with cavitation bubble activity. Experimental and numerical investigations are presented demonstrating the influence of cavitation bubbles on ultrasound propagation. Measurements with a fiber optic hydrofone for pulsed piezoelectric transducers show significant variations in focal pressure waveforms after the first tensile phase of the wave for different gas content. It is supposed that these changes are caused by cavitation effects. Calculations with different bubble densities confirm these experimental results and demonstrate that the first positive pressure part of the wave is not affected by bubble activity. Increasing the gas content leads to a truncated tensile part followed by augmented pressure oscillations. Further on, simulation results for the evolution and impact of cavitation bubble clouds in CW applications are presented.
Modeling the dynamics of single-bubble sonoluminescence
Vignoli, Lucas L; ThomÕ, Roberto C A; Nogueira, A L M A; Paschoal, Ricardo C; Rodrigues, Hilario
Sonoluminescence (SL) is the phenomenon in which acoustic energy is (partially) transformed into light. It may occur by means of many or just one bubble of gas inside a liquid medium, giving rise to the terms multi-bubble- and single-bubble sonoluminescence (MBSL and SBSL). In the last years some models have been proposed to explain this phenomenon, but there is still no complete theory for the light emission mechanism (especially in the case of SBSL). In this work, we will not address this more complicated particular issue, but only present a simple model describing the dynamical behaviour of the sonoluminescent bubble, in the SBSL case. Using simple numerical techniques within the software Matlab, we discuss solutions considering various possibilities for some of the parameters involved: liquid compressibility, superficial tension, viscosity, and type of gas. The model may be used as an introductory study of sonoluminescence in physics courses at undergraduate or graduate levels, as well as a quite clarifyi...
Rheological behaviour of suspensions of bubbles in yield stress fluids
Lucie DuclouÕ; Olivier Pitois; Julie Goyon; Xavier Chateau; Guillaume Ovarlez
The rheological properties of suspensions of bubbles in yield stress fluids are investigated through experiments on model systems made of monodisperse bubbles dispersed in concentrated emulsions. Thanks to this highly tunable system, the bubble size and the rheological properties of the suspending yield stress fluid are varied over a wide range. We show that the macroscopic response under shear of the suspensions depends on the gas volume fraction and the bubble stiffness in the suspending fluid. This relative stiffness can be quantified through capillary numbers comparing the capillary pressure to stress scales associated with the rheological properties of the suspending fluid. We demonstrate that those capillary numbers govern the decrease of the elastic and loss moduli, the absence of variation of the yield stress and the increase of the consistency with the gas volume fraction, for the investigated range of capillary numbers. Micro-mechanical estimates are consistent with the experimental data and provide insight on the experimental results.
Experimental observations of bubble response and light intensity near the threshold for single bubble sonoluminescence in an air-water system
D. Felipe Gaitan; R. Holt
Single bubble sonoluminescence in an air-water system has been shown to occur along a unique surface in the acoustic pressure-ambient radius-gas concentration parameter space where the bubble is stable both in shape and in ~average! size. In this paper, we show how the bubble deviates from the expected path ~traced by the shape-instability threshold as a function of pressure !
Bubble Formation from Wall Orifice in Liquid Cross-Flow Under Low Gravity
NASA Technical Reports Server (NTRS)
Nahra, Henry K.; Kamotani, Y.
Two-phase flows present a wide variety of applications for spacecraft thermal control systems design. Bubble formation and detachment is an integral part of the two phase flow science. The objective of the present work is to experimentally investigate the effects of liquid cross-flow velocity, gas flow rate, and orifice diameter on bubble formation in a wall-bubble injection configuration. Data were taken mainly under reduced gravity conditions but some data were taken in normal gravity for comparison. The reduced gravity experiment was conducted aboard the NASA DC-9 Reduced Gravity Aircraft. The results show that the process of bubble formation and detachment depends on gravity, the orifice diameter, the gas flow rate, and the liquid cross-flow velocity. The data are analyzed based on a force balance, and two different detachment mechanisms are identified. When the gas momentum is large, the bubble detaches from the injection orifice as the gas momentum overcomes the attaching effects of liquid drag and inertia. The surface tension force is much reduced because a large part of the bubble pinning edge at the orifice is lost as the bubble axis is tilted by the liquid flow. When the gas momentum is small, the force balance in the liquid flow direction is important, and the bubble detaches when the bubble axis inclination exceeds a certain angle.
Ex vivo bubble production from ovine large blood vessels: size on detachment and evidence of "active spots".
Arieli, R; Marmur, A
Nanobubbles formed on the hydrophobic silicon wafer were shown to be the source of gas micronuclei from which bubbles evolved during decompression. Bubbles were also formed after decompression on the luminal surface of ovine blood vessels. Four ovine blood vessels: aorta, pulmonary vein, pulmonary artery, and superior vena cava, were compressed to 1013 kPa for 21 h. They were then decompressed, photographed at 1-s intervals, and bubble size was measured on detachment. There were certain spots at which bubbles appeared, either singly or in a cluster. Mean detachment diameter was between 0.7 and 1.0 mm. The finding of active spots at which bubbles nucleate is a new, hitherto unreported observation. It is possible that these are the hydrophobic spots at which bubbles nucleate, stabilise, and later transform into the gas micronuclei that grow into bubbles. The possible neurological effects of these large arterial bubbles should be further explored. PMID:24933644
Colburn, Richard P. (Pasco, WA)
A device for collecting fission gas released by a failed fuel rod which device uses a filter to pass coolant but which filter blocks fission gas bubbles which cannot pass through the filter due to the surface tension of the bubble.
Effect of compressibility on the rise velocity of an air bubble in porous media
NASA Astrophysics Data System (ADS)
Cihan, Abdullah; Corapcioglu, M. Yavuz
The objective of this study is to develop a theoretical model to analyze the effect of air compressibility on air bubble migration in porous media. The model is obtained by combining the Newton's second law of motion and the ideal gas law assuming that the air phase in the bubble behaves as an ideal gas. Numerical and analytical solutions are presented for various cases of interest. The model results compare favorably with both experimental data and analytical solutions reported in the literature obtained for an incompressible air bubble migration. The results show that travel velocity of a compressible air bubble in porous media strongly depends on the depth of air phase injection. A bubble released from greater depths travels with a slower velocity than a bubble with an equal volume injected at shallower depths. As an air bubble rises up, it expands with decreasing bubble pressure with depth. The volume of a bubble injected at a 1-m depth increases 10% as the bubble reaches the water table. However, bubble volume increases almost twofold when it reaches to the surface from a depth of 10 m. The vertical rise velocity of a compressible bubble approaches that of an incompressible one regardless of the injection depth and volume as it reaches the water table. The compressible bubble velocity does not exceed 18.8 cm/s regardless of the injection depth and bubble volume. The results demonstrate that the effect of air compressibility on the motion of a bubble cannot be neglected except when the air is injected at very shallow depths.
Anomalous Capillary Pressure, Stress, and Stability of Solids-Coated Bubbles.
Kam; Rossen
A two-dimensional theoretical model for solids-coated, or "armored," bubbles shows how the armor can support a liquid-vapor interface of reduced or reversed curvature between the particles, giving the bubble zero or even negative capillary pressure. The inward capillary force pulling the particles into the center of the bubble are balanced by large contact forces between the particles in the armor. Thus the bubble is stabilized against dissolution of gas into surrounding liquid, which otherwise would rapidly collapse the bubble. The stresses between particles in such cases are large and could drive sintering of the particles into a rigid framework. Earlier work on solids-coated bubbles assumed that solids can freely enter or leave the bubble surface as the bubble shrinks or expands. In such a case, armored bubbles would not be stable to gas dissolution into surrounding liquid. A new free-energy analysis, however, suggests that a shrunken bubble would not spontaneously expel a solid particle from its armor to relieve stress and allow the bubble to shrink further. Implications and limitations of the theory are discussed. Copyright 1999 Academic Press. PMID:10222072
Bubbles, Bubbles, Tremors & Trouble: The Bayou Corne Sinkhole
NASA Astrophysics Data System (ADS)
Nunn, J. A.
In May 2012, thermogenic methane bubbles were first observed in Bayou Corne in Assumption Parish, Louisiana. As of July 2013, ninety one bubbling sites have been identified. Gas was also found in the top of the Mississippi River Alluvial Aquifer (MRAA) about 125 ft below the surface. Vent wells drilled into the MRAA have flared more 16 million SCF of gas. Trace amounts of hydrogen sulfide also have been detected. Bayou Corne flows above the Napoleonville salt dome which has been an active area for oil and gas exploration since the 1920s. The dome is also a site of dissolution salt mining which has produced large caverns with diameters of up to 300 ft and heights of 2000 ft. Some caverns are used for storage of natural gas. Microseismic activity was confirmed by an Earthscope seismic station in White Castle, LA in July 2012. An array of microseismic stations set up in the area recorded more than 60 microseismic events in late July and early August, 2012. These microseismic events were located on the western side of the dome. Estimated focal depths are just above the top of salt. In August 2012, a sinkhole developed overnight just to the northwest of a plugged and abandoned brine filled cavern (see figure below). The sinkhole continues to grow in area to more than 20 acres and has consumed a pipeline right of way. The sinkhole is more than 750 ft deep at its center. Microseismic activity was reduced for several months following the formation of the sinkhole. Microseismic events have reoccurred episodically since then with periods of frequent events preceding slumping of material into the sinkhole or a 'burp' where fluid levels in the sinkhole drop and then rebound followed by a decrease in microseismic activity. Some gas and/or oil may appear at the surface of the sinkhole following a 'burp'. Very long period events also have been observed which are believed to be related to subsurface fluid movement. A relief well drilled into the abandoned brine cavern found that it was filling with sediment. From September 2012 to March 2013 the floor of the cavern rose 600 ft and was 90% filled. However, the sediment fill level dropped more than 300 ft in June 2013. A 2007 seismic survey suggests that the bottom of the abandon cavern is close to the edge of the salt dome potentially allowing direct contact with permeable formations. A 3D seismic survey was shot in 2013 to better characterize the subsurface. Long term microseismic, subsidence, water quality and air quality monitoring programs have been established. Ground level photograph of Bayou Corne sinkhole. Note degraded hydrocarbons in water.
Phenomenological model for dispersed bubbly flow in pipes
D. E. Nikitopoulos; Efstathios E. Michaelides
The ability to predict pressure drop as a function of flow parameters for gas-liquid pipe flows in general and dispersed, bubbly, pipe flows in particular is of considerable importance to a number of industries that utilize two-phase flow systems and processes (for instance, petroleum, chemical, nuclear, and geothermal). An analytical approach to the problem of steady-state, axisymmetrically dispersed, bubbly flow