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Solar flare emissions in the chromosphere often appear as elongated ribbons on both sides of the magnetic polarity inversion line (PIL), which has been regarded as evidence of a typical configuration of magnetic reconnection. However, flares having a circular ribbon have rarely been reported, although it is expected in the fan-spine magnetic topology involving reconnection at a three-dimensional (3D) coronal null point. We present five circular ribbon flares with associated surges, using high-resolution and high-cadence H{alpha} blue wing observations obtained from the recently digitized films of Big Bear Solar Observatory. In all the events, a central parasitic magnetic field is encompassed by the opposite polarity, forming a circular PIL traced by filament material. Consequently, a flare kernel at the center is surrounded by a circular flare ribbon. The four homologous jet-related flares on 1991 March 17 and 18 are of particular interest, as (1) the circular ribbons brighten sequentially, with cospatial surges, rather than simultaneously, (2) the central flare kernels show an intriguing 'round-trip' motion and become elongated, and (3) remote brightenings occur at a region with the same magnetic polarity as the central parasitic field and are co-temporal with a separate phase of flare emissions. In another flare on 1991 February 25, the circular flare emission and surge activity occur successively, and the event could be associated with magnetic flux cancellation across the circular PIL. We discuss the implications of these observations combining circular flare ribbons, homologous jets, and remote brightenings for understanding the dynamics of 3D magnetic restructuring.
Wang Haimin; Liu Chang, E-mail: firstname.lastname@example.com [Space Weather Research Laboratory, Center for Solar-Terrestrial Research, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States)
Formation of Jets by Baroclinic Turbulence
Science Conference Proceedings (OSTI)
Turbulent fluids are frequently observed to spontaneously self-organize into large spatial-scale jets; geophysical examples of this phenomenon include the Jovian banded winds and the earth�s polar-front jet. These relatively steady large-scale ...
Brian F. Farrell; Petros J. Ioannou
Modeling of NOx formation in circular laminar jet flames
Emissions of oxides of nitrogen (NOx) from combustion devices is a topic of tremendous current importance. The bulk of the review of NOx emissions has been in the field of turbulent jet flames. However laminar jet flames have provided much insight into the relative importance of NOx reaction pathways in non premixed combustion for various flame conditions. The existing models include detailed chemistry kinetics for various species involved in the flame. These detailed models involve very complex integration of hundreds of chemical reactions of various species and their intermediates. Hence such models are highly time consuming and also normally involve heavy computational costs. This work proposes a numerical model to compute the total production of NOx in a non-premixed isolated circular laminar jet flame. The jet consists of the fuel rich inner region and the O2 rich outer region. The model estimates both thermal NOx and prompt NOx assuming single step kinetics for NOx formation and a thin flame model. Further the amount of air entrainment by jet depends upon the Sc number of fuel. The higher the Sc number, the higher is the air entrained which lowers the flame temperature and hence NOx formation. With increasing Sc number, flame volume increases which leads to an increase in the NOx formation. The effect of the Sc number variation on the net production of NOx and flame structure is also investigated. The effect of equilibrium chemistry for CO2 CO + 1/2 O2 and H2O H2 +1/2 O2 on total NOx emission is studied. Also the effect of both CO2 and H2O equilibrium is considered simultaneously and the net x NO formation for propane is 45 ppm. The split between pre-flame and post-flame regions is also investigated. For Propane, 96% of NO emissions occur in the pre-flame region and about 4% in the post-flame region. The model predictions are compared with experimental values of NOx missions reported elsewhere.
Siwatch, Vivek
Structure and Spacing of Jets in Barotropic Turbulence
Science Conference Proceedings (OSTI)
Turbulent flows are often observed to be organized into large-spatial-scale jets such as the familiar zonal jets in the upper levels of the Jovian atmosphere. These relatively steady large-scale jets are not forced coherently but are maintained ...
Brian F. Farrell; Petros J. Ioannou
Dynamics of quasi-two-dimensional turbulent jets
they can provide, jets have been used in various indus- trial applications, such as waste water disposal (Yannopoulos, 2006), chemical reactors (Jirka & Harleman, 1979), or as a means of propulsion (Stanley, Sarkar & Mellado, 2002). In geophysical flows... .1 Introduction The study of turbulent plane jets is relevant to a wide variety of problems where both qualitative and quantitative knowledge of the concentration in time and space of tracers transported by the jet is needed (Kotsovinos, 1975). In many industrial...
Landel, Julien R�my Dominique G�rard
Emergence of Jets from Turbulence in the Shallow-Water Equations on an Equatorial Beta Plane
Science Conference Proceedings (OSTI)
Coherent jets, such as the Jovian banded winds, are a prominent feature of rotating turbulence. Shallow-water turbulence models capture the essential mechanism of jet formation, which is systematic eddy momentum flux directed up the mean velocity ...
Brian F. Farrell; Petros J. Ioannou
Jet impingement has been shown to be an effective method for enhancing convective heat transfer. There are a variety of applications of impinging jets in industry, including tempering and shaping of glass, annealing of metal and plastic sheets, cooling of electronic components and drying of paper, veneer, etc. Another application is the use of impinging jets in internal cooling channels in modern gas turbine blades. High velocity jets provide an effective way to augment the rate of heat removal from the blades to the cooling air, maintaining the blade temperatures within tolerable and metallurgical limits. This experimental research examines, for turbulent parallel and counter flows of air through an annular channel with holes for jet impingement along the inner tube, the effects of varying the geometries of the channel and the hole array, and the air flow rate, on the heat transfer distribution on the inner surfaces of the outer tube. Air enters one end of the inner tube, whose other end is closed, passes through the holes on the inner tube and exits through one end of the annular passage between the inner and outer tubes. Each hole array has inline or staggered circular holes with a given diameter and has a fixed number of holes around the circumference of the inner tube at any cross section of the annular channel. Heat transfer experiments are performed for Reynolds numbers of 5,000, 12,250 and 30,000 to determine the distribution of the regionally average Nusselt numbers along the outer tube, as a result of the impinging jets along the inner tube. Pressure measurement experiments give the pressure distributions in the airflows in the inner tube and between the inner and outer tubes. The pressure data is needed to determine the mass flow rates of the impinging jets along the inner tube. The results of the experiments are presented and discussed, the Nusselt numbers for the various cases studied are compared and major findings are reported. The results of this investigation should be particularly useful to engineers in the design of the leading edges of airfoils of modern gas turbine blades.
Mhetras, Shantanu Prakash
Effects of inclined jets on turbulent oxy-flame characteristics in a triple jet burner
Science Conference Proceedings (OSTI)
The reactants are generally injected into the industrial furnaces by jets. An effective method to act on combustion in such systems is to control the way injection jets. The present study concerns the control of turbulent flames by the jets deflection in a natural gas-oxygen burner with separated jets. The burner of 25 kW power is constituted with three aligned jets, one central natural gas jet surrounded by two oxygen jets. The principal idea is to confine the fuel jet by oxygen jets to favour the mixing in order to improve the flame stability and consequently to reduce the pollutant emissions like NO{sub x}. The flame stability and its structural properties are analyzed by the OH chemiluminescence. The Particle Image Velocimetry technique has been used to characterize the dynamic field. Results show that the control by inclined jets has a considerable effect on the dynamic behaviour and flame topology. Indeed, the control by incline of oxygen jets towards fuel jet showed a double interest: a better stabilization of flame and a significant reduction of nitrogen oxides. Measurements showed that the deflection favours the mixing and accelerates the fusion of jets allowing the flame stabilization. (author)
Boushaki, T.; Mergheni, M.A.; Sautet, J.C. [CORIA UMR 6614 CNRS-Universite et INSA de ROUEN, Avenue de l'Universite, 76 801 Saint Etienne du Rouvray, Cedex (France); Labegorre, B. [Air Liquide CRCD, Les Loges en Josas, BP 126, 78350 Jouy en Josas (France)
Multiple mapping conditioning of velocity in turbulent jet flames
Science Conference Proceedings (OSTI)
Multiple mapping conditioning (MMC) has emerged as a new approach to model turbulent reacting flows. This study revises the standard MMC closure for velocity in turbulent jet flows from linearity in the reference space to linearity in the composition space. This modeling amendment ensures that the standard velocity model in conditional moment closure studies can now be used for MMC computation as well. A simplified model for the velocity-dependence of MMC drift coefficients is derived without loss of generality and is implemented for the revised velocity closure. Modeling results have been corroborated against the Direct Numerical Simulation database of a spatially evolving, planar turbulent jet flame. The revised model shows marked improvement over standard MMC closure in predicting velocity statistics close to the nozzle. (author)
Vaishnavi, P. [Mechanical Engineering Department, Imperial College, London SW7 2AZ (United Kingdom); Kronenburg, A. [Institut fuer Technische Verbrennung, Universitaet Stuttgart, 70174 Stuttgart (Germany)
Magnetohydrodynamic lattice Boltzmann simulations of turbulence and rectangular jet flow
Magnetohydrodynamic (MHD) investigations of decaying isotropic turbulence and rectangular jets (RJ) are carried out. A novel MHD lattice Boltzmann scheme that combines multiple relaxation time (MRT) parameters for the velocity field with a single relaxation time (SRT) parameter for the Maxwell�s stress tensor is developed for this study. In the MHD homogeneous turbulence studies, the kinetic/magnetic energy and enstrophy decays, kinetic enstrophy evolution, and vorticity alignment with the strain-rate tensor are evaluated to assess the key physical MHD turbulence mechanisms. The magnetic and kinetic energies interact and exchange through the influence of the Lorentz force work. An initial random fluctuating magnetic field increases the vortex stretching and forward cascade mechanisms. A strong uniform mean magnetic field increases the anisotropy of the turbulent flow field and causes inverse cascading. In the RJ studies, an investigation into the MHD effects on velocity, instability, and the axis-switching phenomena is performed at various magnetic field strengths and Magnetic Reynolds Numbers. The magnetic field is found to decelerate the jet core, inhibit instability, and prevent axis-switching. The key physical mechanisms are: (i) the exchange of energy between kinetic and magnetic modes and (ii) the magnetic field effect on the vorticity evolution. From these studies, it is found that magnetic field influences momentum, vorticity, and energy evolution and the degree of modification depends on the field strength. This interaction changes vortex evolution, and alters turbulence processes and rectangular jet flow characteristics. Overall, this study provides more insight into the physics of MHD flows, which suggests possible applications of MHD Flow Control.
Riley, Benjamin Matthew
Equatorial Jets in Decaying Shallow-Water Turbulence on a Rotating Sphere
Science Conference Proceedings (OSTI)
Ensemble experiments of decaying shallow-water turbulence on a rotating sphere are performed to confirm the robustness of the emergence of an equatorial jet. While previous studies have reported that the equatorial jets emerging in shallow-water ...
Yuji Kitamura; Keiichi Ishioka
Stability Regimes of Turbulent Nitrogen-Diluted Hydrogen Jet Flames
One option for combustion in zero-emission Integrated Gasification Combined Cycle (IGCC) power plants is non-premixed combustion of nitrogen-diluted hydrogen in air. An important aspect to non-premixed combustion is flame stability or anchoring, though only a few fundamental stability studies of these flames have taken place to date. The following paper presents the results of experiments investigating the effects of nitrogen diluent fraction, jet diameter, and exit velocity on the static stability limits of a turbulent hydrogen jet flame issuing from a thin-lipped tube into a quiescent atmosphere. Four different stability limits are observed: detachment from the burner lip, reattachment to the burner lip, transition from a laminar lifted flame base to blowout or to a turbulent lifted flame, and transition from a turbulent lifted flame to blowout. The applicability of existing theories and correlations to the stability results is discussed. These results are an important step in assessing the viability of a non-premixed combustion approach using hydrogen diluted with nitrogen as a fuel.
Weiland, N.T.; Strakey, P.A.
Science Conference Proceedings (OSTI)
A plane, chemically reacting jet of fuel injected through a narrow spanwise slot into supersonic and fully turbulent air flow in a channel with isothermal, parallel walls is investigated using a semi-implicit large-eddy simulation technique. It is based ... Keywords: high-order numerical schemes, infinitely fast chemistry, large-eddy simulation, plane jet in crossflow, supersonic turbulent channel flow
Ch. Schaupp; R. Friedrich
This study describes the spatial distribution of sediment deposition in the wake of a circular patch of model vegetation and the effect of the patch on turbulence and mean flow. Two difference types pf vegetation were used ...
Ortiz, Alejandra C
Science Conference Proceedings (OSTI)
The autoignition of hydrogen/carbon monoxide in a turbulent jet with preheated co-flow air is studied using the one-dimensional turbulence (ODT) model. The simulations are performed at atmospheric pressure based on varying the jet Reynolds number and the oxidizer preheat temperature for two compositions corresponding to varying the ratios of H{sub 2} and CO in the fuel stream. Moreover, simulations for homogeneous autoignition are implemented for similar mixture conditions for comparison with the turbulent jet results. The results identify the key effects of differential diffusion and turbulence on the onset and eventual progress of autoignition in the turbulent jets. The differential diffusion of hydrogen fuels results in a reduction of the ignition delay relative to similar conditions of homogeneous autoignition. Turbulence may play an important role in delaying ignition at high-turbulence conditions, a process countered by the differential diffusion of hydrogen relative to carbon monoxide; however, when ignition is established, turbulence enhances the overall rates of combustion of the non-premixed flame downstream of the ignition point. (author)
Gupta, Kamlesh G.; Echekki, Tarek [Department of Mechanical and Aerospace Engineering, North Carolina State University, NC (United States)
Deposition of micron liquid droplets on wall in impinging turbulent air jet
The fluid mechanics of the deposition of micron liquid (olive oil) droplets on a glass wall in an impinging turbulent air jet is studied experimentally. The spatial patterns of droplets deposited on a wall are measured by ...
Liu, Tianshu
Science Conference Proceedings (OSTI)
Formation of multiple jets in forced beta-plane turbulence is studied from the perspective of nonuniform nonconservative arrangement of potential vorticity (PV). Numerical simulations are analyzed to show that mixing and forcing reinforce jets by ...
Noboru Nakamura; Da Zhu
Sensitivity of Perturbation Variance and Fluxes in Turbulent Jets to Changes in the Mean Jet
Science Conference Proceedings (OSTI)
Synoptic-scale eddy variance and fluxes of heat and momentum in midlatitude jets are sensitive to small changes in mean jet velocity, dissipation, and static stability. In this work the change in the jet producing the greatest increase in ...
Brian F. Farrell; Petros J. Ioannou
Leading Lyapunov Vectors of a Turbulent Baroclinic Jet in a Quasigeostrophic Model
Science Conference Proceedings (OSTI)
Leading Lyapunov exponents and vectors are calculated for a turbulent baroclinic jet in a quasigeostrophic model with O(105) degrees of freedom. The leading exponent is close to 0.4 day?1, and the unstable subspace has dimension between 30 and ...
Chris Snyder; Thomas M. Hamill
Barotropic Beta-Plane Turbulence in a Regime with Strong Zonal Jets Revisited
Science Conference Proceedings (OSTI)
The problem of quantification of barotropic beta-plane turbulence driven by small-scale stochastic forcing into regimes dominated by quasi-periodic zonal jets is revisited. It is shown that the large-scale relative vorticity in such regimes is ...
S. Danilov; V. M. Gryanik
Evolution of a confined turbulent jet in a long cylindrical cavity: Homogeneous fluids
Science Conference Proceedings (OSTI)
The flow induced in a long cylinder by an axially discharging round turbulent jet was investigated experimentally with applications to crude oil storage in the U.S. strategic petroleum reserves (SPR). It was found that the flow does not reach a true steady state
S. I. Voropayev; X. Sanchez; S. Webb; H. J. S. Fernando
Turbulent fluid jet excavation in cohesive soil : with particular application to jet grouting
This thesis reviews the jet grouting methodology, and the current state of practice and research. Current methods of prediction of jet grout diameters are highly empirical and site specific, and do not take into account ...
Ho, Chu Eu
Jet Formation and Evolution in Baroclinic Turbulence with Simple Topography
Science Conference Proceedings (OSTI)
Satellite altimetry and high-resolution ocean models indicate that the Southern Ocean comprises an intricate web of narrow, meandering jets that undergo spontaneous formation, merger, and splitting events, as well as rapid latitude shifts over ...
Andrew F. Thompson
Composition PDF/photon Monte Carlo modeling of moderately sooting turbulent jet flames
A comprehensive model for luminous turbulent flames is presented. The model features detailed chemistry, radiation and soot models and state-of-the-art closures for turbulence-chemistry interactions and turbulence-radiation interactions. A transported probability density function (PDF) method is used to capture the effects of turbulent fluctuations in composition and temperature. The PDF method is extended to include soot formation. Spectral gas and soot radiation is modeled using a (particle-based) photon Monte Carlo method coupled with the PDF method, thereby capturing both emission and absorption turbulence-radiation interactions. An important element of this work is that the gas-phase chemistry and soot models that have been thoroughly validated across a wide range of laminar flames are used in turbulent flame simulations without modification. Six turbulent jet flames are simulated with Reynolds numbers varying from 6700 to 15,000, two fuel types (pure ethylene, 90% methane-10% ethylene blend) and different oxygen concentrations in the oxidizer stream (from 21% O{sub 2} to 55% O{sub 2}). All simulations are carried out with a single set of physical and numerical parameters (model constants). Uniformly good agreement between measured and computed mean temperatures, mean soot volume fractions and (where available) radiative fluxes is found across all flames. This demonstrates that with the combination of a systematic approach and state-of-the-art physical models and numerical algorithms, it is possible to simulate a broad range of luminous turbulent flames with a single model. (author)
Mehta, R.S.; Haworth, D.C.; Modest, M.F. [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)
Science Conference Proceedings (OSTI)
Three-dimensional numerical simulations of freely evolving stratified geostrophic turbulence on the ? plane are presented as a simplified model of zonal jet formation on Jupiter. This study samples the parameter space that covers the low, middle, ...
Kunio M. Sayanagi; Adam P. Showman; Timothy E. Dowling
Simulations of multi-phase turbulence in jet cocoons
The interaction of optically emitting clouds with warm X-ray gas and hot, tenuous radio plasma in radio jet cocoons is modelled by 2D compressible hydrodynamic simulations. The initial setup is the Kelvin-Helmholtz instability at a contact surface of density contrast 10,000. The denser medium contains clouds of higher density. Optically thin radiation is realised via a cooling source term. The cool phase effectively extracts energy from the other gas which is both, radiated away and used for acceleration of the cold phase. This increases the system's cooling rate substantially and leads to a massively amplified cold mass dropout. We show that it is feasible, given small seed clouds of order 100 solar masses, that all of the optically emitting gas in a radio jet cocoon may be produced by this mechanism on the propagation timescale of the jet. The mass is generally distributed as T^-1/2 with temperature, with a prominent peak at 14,000 K. This peak is likely to be related to the counteracting effects of shock heating and a strong rise in the cooling function. The volume filling factor of cold gas in this peak is of the order 10^-5 to 10^-3 and generally increases during the simulation time. The simulations tend towards an isotropic scale free Kolmogorov-type energy spectrum over the simulation timescale. We find the same Mach-number density relation as Kritsuk & Norman (2004) and show that this relation may explain the velocity widths of emission lines associated with high redshift radio galaxies, if the environmental temperature is lower, or the jet-ambient density ratio is less extreme than in their low redshift counterparts.
Martin Krause; Paul Alexander
Understanding and predicting soot generation in turbulent non-premixed jet flames.
This report documents the results of a project funded by DoD's Strategic Environmental Research and Development Program (SERDP) on the science behind development of predictive models for soot emission from gas turbine engines. Measurements of soot formation were performed in laminar flat premixed flames and turbulent non-premixed jet flames at 1 atm pressure and in turbulent liquid spray flames under representative conditions for takeoff in a gas turbine engine. The laminar flames and open jet flames used both ethylene and a prevaporized JP-8 surrogate fuel composed of n-dodecane and m-xylene. The pressurized turbulent jet flame measurements used the JP-8 surrogate fuel and compared its combustion and sooting characteristics to a world-average JP-8 fuel sample. The pressurized jet flame measurements demonstrated that the surrogate was representative of JP-8, with a somewhat higher tendency to soot formation. The premixed flame measurements revealed that flame temperature has a strong impact on the rate of soot nucleation and particle coagulation, but little sensitivity in the overall trends was found with different fuels. An extensive array of non-intrusive optical and laser-based measurements was performed in turbulent non-premixed jet flames established on specially designed piloted burners. Soot concentration data was collected throughout the flames, together with instantaneous images showing the relationship between soot and the OH radical and soot and PAH. A detailed chemical kinetic mechanism for ethylene combustion, including fuel-rich chemistry and benzene formation steps, was compiled, validated, and reduced. The reduced ethylene mechanism was incorporated into a high-fidelity LES code, together with a moment-based soot model and models for thermal radiation, to evaluate the ability of the chemistry and soot models to predict soot formation in the jet diffusion flame. The LES results highlight the importance of including an optically-thick radiation model to accurately predict gas temperatures and thus soot formation rates. When including such a radiation model, the LES model predicts mean soot concentrations within 30% in the ethylene jet flame.
Wang, Hai (University of Southern California, Los Angeles, CA); Kook, Sanghoon; Doom, Jeffrey; Oefelein, Joseph Charles; Zhang, Jiayao; Shaddix, Christopher R.; Schefer, Robert W.; Pickett, Lyle M.
Global NOx Measurements in Turbulent Nitrogen-Diluted Hydrogen Jet Flames
Turbulent hydrogen diffusion flames diluted with nitrogen are currently being studied to assess their ability to achieve the DOE Turbine Program�s aggressive emissions goal of 2 ppm NOx in a hydrogen-fueled IGCC gas turbine combustor. Since the unstrained adiabatic flame temperatures of these diluted flames are not low enough to eliminate thermal NOx formation the focus of the current work is to study how the effects of flame residence time and global flame strain can be used to help achieve the stated NOx emissions goal. Dry NOx measurements are presented as a function of jet diameter nitrogen dilution and jet velocity for a turbulent hydrogen/nitrogen jet issuing from a thin-lipped tube in an atmospheric pressure combustor. The NOx emission indices from these experiments are normalized by the flame residence time to ascertain the effects of global flame strain and fuel Lewis Number on the NOx emissions. In addition dilute hydrogen diffusion flame experiments were performed in a high-pressure combustor at 2 4 and 8 atm. The NOx emission data from these experiments are discussed as well as the results from a Computational Fluid Dynamics modeling effort currently underway to help explain the experimental data.
Weiland, N.T.; Strakey, P.A.
Science Conference Proceedings (OSTI)
A NOAA P-3 research aircraft collected measurements in a storm off of the U.S. West Coast that featured a low-level jet with wind speeds approaching 50 m s?1. These measurements have been used to document mean and turbulent boundary layer ...
Nicholas A. Bond; Bernard A. Walter
Science Conference Proceedings (OSTI)
In the nighttime stable boundary layer (SBL), shear and turbulence are generated in the layer between the maximum of the low-level jet (LLJ) and the earth's surface. Here, it is investigated whether gross properties of the LLJ�its height and ...
Robert M. Banta; Yelena L. Pichugina; Rob K. Newsom
Mechanisms of Flame Stabilization and Blowout in a Reacting Turbulent Hydrogen Jet in Cross-Flow
The mechanisms contributing to flame stabilization and blowout in a nitrogen-diluted hydrogen transverse jet in a turbulent boundary layer cross-flow (JICF) are investigated using three-dimensional direct numerical simulation (DNS) with detailed chemistry. Non-reacting JICF DNS were performed to understand the relative magnitude and physical location of low velocity regions on the leeward side of the fuel jet where a flame can potentially anchor. As the injection angle is reduced from 90{sup o} to 70{sup o}, the low velocity region was found to diminish significantly, both in terms of physical extent and magnitude, and hence, its ability to provide favorable conditions for flame anchoring and stabilization are greatly reduced. In the reacting JICF DNS a stable flame is observed for 90{sup o} injection angle and, on average, the flame root is in the vicinity of low velocity magnitude and stoichiometric mixture. When the injection angle is smoothly transitioned to 75{sup o} a transient flame blowout is observed. Ensemble averaged quantities on the flame base reveal two phases of the blowout characterized by a kinematic imbalance between flame propagation speed and flow normal velocity. In the first phase dominant flow structures repeatedly draw the flame base closer to the jet centerline resulting in richer-than-stoichiometric mixtures and high velocity magnitudes. In the second phase, in spite of low velocity magnitudes and a return to stoichiometry, due to jet bending and flame alignment normal to the cross-flow, the flow velocity normal to the flame base increases dramatically perpetuating the blowout.
Kolla, H.; Grout, R. W.; Gruber, A.; Chen, J. H.
Measurements of soot, OH, and PAH concentrations in turbulent ethylene/air jet flames
Science Conference Proceedings (OSTI)
This paper presents results from an investigation of soot formation in turbulent, non-premixed, C{sub 2}H{sub 4}/air jet flames. Tests were conducted using a H{sub 2}-piloted burner with fuel issuing from a 2.18 mm i.d. tube into quiescent ambient air. A range of test conditions was studied using the initial jet velocity (16.2-94.1 m/s) as a parameter. Fuel-jet Reynolds numbers ranged from 4000 to 23,200. Planar laser-induced incandescence (LII) was employed to determine soot volume fractions, and laser-induced fluorescence (LIF) was used to measure relative hydroxyl radical (OH) concentrations and polycyclic aromatic hydrocarbons (PAHs) concentrations. Extensive information on the structure of the soot and OH fields was obtained from two-dimensional imaging experiments. Quantitative measurements were obtained by employing the LII and LIF techniques independently. Imaging results for soot, OH, and PAH show the existence of three soot formation/oxidation regions: a rapid soot growth region, in which OH and soot particles lie in distinctly different radial locations; a mixing-dominated region controlled by large-scale motion; and a soot-oxidation region in which the OH and soot fields overlap spatially, resulting in the rapid oxidation of soot particles. Detailed quantitative analyzes of soot volume fractions and OH and soot zone thicknesses were performed along with the temperature measurement using the N{sub 2}-CARS system. Measurements of OH and soot zone thicknesses show that the soot zone thickness increases linearly with axial distance in the soot formation region, whereas the OH zone thickness is nearly constant in this region. The OH zone thickness then rapidly increases with downstream distance and approximately doubles in the soot-oxidation region. Probability density functions also were obtained for soot volume fractions and OH concentrations. These probability density functions clearly define the spatial relationships among the OH, PAH concentrations, the soot formation, and oxidation processes. (author)
Lee, Seong-Young [Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 (United States); Turns, Stephen R.; Santoro, Robert J. [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States)
Direct numerical simulation (DNS) of the near-field of a three-dimensional spatially-developing turbulent ethylene jet flame in highly-heated coflow is performed with a reduced mechanism to determine the stabilization mechanism. The DNS was performed at a jet Reynolds number of 10,000 with over 1.29 billion grid points. The results show that auto-ignition in a fuel-lean mixture at the flame base is the main source of stabilization of the lifted jet flame. The Damkoehler number and chemical explosive mode (CEM) analysis also verify that auto-ignition occurs at the flame base. In addition to auto-ignition, Lagrangian tracking of the flame base reveals the passage of large-scale flow structures and their correlation with the fluctuations of the flame base similar to a previous study (Yoo et al., J. Fluid Mech. 640 (2009) 453-481) with hydrogen/air jet flames. It is also observed that the present lifted flame base exhibits a cyclic 'saw-tooth' shaped movement marked by rapid movement upstream and slower movement downstream. This is a consequence of the lifted flame being stabilized by a balance between consecutive auto-ignition events in hot fuel-lean mixtures and convection induced by the high-speed jet and coflow velocities. This is confirmed by Lagrangian tracking of key variables including the flame-normal velocity, displacement speed, scalar dissipation rate, and mixture fraction at the stabilization point.
Yoo, Chun S [Sandia National Laboratories (SNL)
NLE Websites -- All DOE Office Websites (Extended Search)
protons protons top quark bottom quark muon top quark antiprotons bottom quark low energy muon quark quark - W boson + Jet Jet Jet Jet neutrino W boson particles antiparticles A Top Antitop Quark Event from the D-Zero Detector at Fermilab muon low energy muon Jet Jet Jet Jet particles antiparticles Particles Seen by the D-Zero Detector at Fermilab in a Top Antitop Quark Event. DST LEGO 16-JUL-1996 15:32 Run 92704 Event 14022 9-JUL-1995 13:17 MUON MUON Miss ET ET DST ETA-PHI 4 MUON 1 MISS ET 4 JET (HAD) (EM) D-Zero Detector at Fermi National Accelerator Laboratory Lego Plot CAL+TKS END VIEW 16-JUL-1996 15:33 Run 92704 Event 14022 9-JUL-1995 13:17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Science Conference Proceedings (OSTI)
In this study, first results of the heat transfer characteristic of a vertical double tube heat exchanger were determined. The heat exchanger was operated under cocurrent-flow conditions. The Reynolds-number was varied in the transition region between ... Keywords: circular tube, forced convection, heat transfer, transition region
D. Huber; H. Walter
In order to understand the heat transfer characteristics of molten salt and testify the validity of the well-known empirical convective heat transfer correlations, experimental study on transition convective heat transfer with molten salt in a circular tube was conducted. Molten salt circulations were realized and operated in a specially designed system over 1000 h. The average forced convective heat transfer coefficients of molten salt were determined by least-squares method based on the measured data of flow rates and temperatures. Finally, a heat transfer correlation of transition flow with molten salt in a circular tube was obtained and good agreement was observed between the experimental data of molten salt and the well-known correlations presented by Hausen and Gnielinski, respectively. (author)
Yu-ting, Wu; Bin, Liu; Chong-fang, Ma; Hang, Guo [Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education and Key Laboratory of Heat Transfer and Energy Conversion, Beijing municipality, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100022 (China)
Transported PDF Modeling of Nonpremixed Turbulent CO/H-2/N-2 Jet Flames
Science Conference Proceedings (OSTI)
Turbulent CO/H{sub 2}/N{sub 2} (�syngas�) flames are simulated using a transported composition probability density function (PDF) method. A consistent hybrid Lagrangian particle/Eulerian mesh algorithm is used to solve the modeled PDF transport equation. The model includes standard k�? turbulence, gradient transport for scalars, and Euclidean minimum spanning tree (EMST) mixing. Sensitivities of model results to variations in the turbulence model, the treatment of radiation heat transfer, the choice of chemical mechanism, and the PDF mixing model are explored. A baseline model reproduces the measured mean and rms temperature, major species, and minor species profiles reasonably well, and captures the scaling that is observed in the experiments. Both our results and the literature suggest that further improvements can be realized with adjustments in the turbulence model, the radiation heat transfer model, and the chemical mechanism. Although radiation effects are relatively small in these flames, consideration of radiation is important for accurate NO prediction. Chemical mechanisms that have been developed specifically for fuels with high concentrations of CO and H{sub 2} perform better than a methane mechanism that was not designed for this purpose. It is important to account explicitly for turbulence�chemistry interactions, although the details of the mixing model do not make a large difference in the results, within reasonable limits.
Zhao, xinyu; Haworth, D. C.; Huckaby, E. David
This study examines the effect of acoustic excitation using forced coaxial air on the flame characteristics of turbulent hydrogen non-premixed flames. A resonance frequency was selected to acoustically excite the coaxial air jet due to its ability to effectively amplify the acoustic amplitude and reduce flame length and NO{sub x} emissions. Acoustic excitation causes the flame length to decrease by 15% and consequently, a 25% reduction in EINO{sub x} is achieved, compared to coaxial air flames without acoustic excitation at the same coaxial air to fuel velocity ratio. Moreover, acoustic excitation induces periodical fluctuation of the coaxial air velocity, thus resulting in slight fluctuation of the fuel velocity. From phase-lock PIV and OH PLIF measurement, the local flow properties at the flame surface were investigated under acoustic forcing. During flame-vortex interaction in the near field region, the entrainment velocity and the flame surface area increased locally near the vortex. This increase in flame surface area and entrainment velocity is believed to be a crucial factor in reducing flame length and NO{sub x} emission in coaxial jet flames with acoustic excitation. Local flame extinction occurred frequently when subjected to an excessive strain rate, indicating that intense mass transfer of fuel and air occurs radially inward at the flame surface. (author)
Kim, Munki; Choi, Youngil; Oh, Jeongseog; Yoon, Youngbin [School of Mechanical and Aerospace Engineering, Seoul National University, Seoul (Korea)
A Statistical Description of Small-Scale Turbulence in the Low-Level Nocturnal Jet
Science Conference Proceedings (OSTI)
The probability density function (PDF) and spatial statistics of both the energy dissipation rate ? and the temperature structure constant C2T are determined for the shear region of a nocturnal jet. The PDF of ? and C2T are approximately lognormal. In ...
Rod Frehlich; Yannick Meillier; Michael L. Jensen; Ben Balsley
NLE Websites -- All DOE Office Websites (Extended Search)
Turbulence Turbulence in Alcator C-Mod and Wendelstein 7-AS plasmas during controlled confinement transitions N.P.Basse, E.M.Edlund, C.L.Fiore, M.J.Greenwald, A.E.Hubbard, J.W.Hughes, J.H.Irby, G.J.Kramer 1 , L.Lin, Y.Lin, A.G.Lynn 2 , E.S.Marmar, D.R.Mikkelsen 1 , D.Mossessian, P.E.Phillips 2 , M.Porkolab, J.E.Rice, W.L.Rowan 2 , J.A.Snipes, J.L.Terry, S.M.Wolfe, S.J.Wukitch, K.Zhurovich, S.Zoletnik 3 and the C-Mod and W7-AS 4 Teams MIT Plasma Science and Fusion Center, Cambridge, USA 1 Princeton Plasma Physics Laboratory, Princeton, USA 2 University of Texas at Austin, Austin, USA 3 KFKI-RMKI, EURATOM Association, Budapest, Hungary 4 Max-Planck-Institut f¨ ur Plasmaphysik, EURATOM Association, Greifswald, Germany At certain values of the edge rotational transform, ι a = 1/q a , the confinement time of plasmas in the Wendelstein 7-AS (W7-AS) stellarator was found to
Science Conference Proceedings (OSTI)
Profiles of mean winds and turbulence were measured by the High Resolution Doppler lidar in the strong-wind stable boundary layer (SBL) with continuous turbulence. The turbulence quantity measured was the variance of the streamwise wind velocity ...
Robert M. Banta; Yelena L. Pichugina; W. Alan Brewer
Three dimensional analysis of turbulent steam jets in enclosed structures : a CFD approach.
This paper compares the three-dimensional numerical simulation with the experimental data of a steam blowdown event in a light water reactor containment building. The temperature and pressure data of a steam blowdown event was measured at the Purdue University Multi-Dimensional Integrated Test Assembly (PUMA), a scaled model of the General Electric simplified Boiling Water Reactor. A three step approach was used to analyze the steam jet behavior. First, a 1-Dimensional, system level RELAP5/Mod3.2 model of the steam blowdown event was created and the results used to set the initial conditions for the PUMA blowdown experiments. Second, 2-Dimensional CFD models of the discharged steam jets were computed using PHOENICS, a commercially available CFD package. Finally, 3-Dimensional model of the PUMA drywell was created with the boundary conditions based on experimental measurements. The results of the 1-D and 2-D models were reported in the previous meeting. This paper discusses in detail the formulation and the results of the 3-Dimensional PHOENICS model of the PUMA drywell. It is found that the 3-D CFD solutions compared extremely well with the measured data.
Ishii, M.; NguyenLe, Q.
Numerical Simulations of Boiling Jet Impingement Cooling in Power Electronics
This paper explores turbulent boiling jet impingement for cooling power electronic components in hybrid electric vehicles.
Narumanchi, S.; Troshko, A.; Hassani, V.; Bharathan, D.
This paper explores effects of differential diffusion in nonpremixed turbulent jet flames. Pulsed Raman scattering spectroscopy is used to measure temperature and species concentrations in chemically reacting jets of H{sub 2}/CO{sub 2} into air, over a range of jet Reynolds numbers from 1,000 to 30,000 based on cold jet fluid properties. Results show significant effects of differential diffusion at all jet Reynolds numbers considered. Differential diffusion between H{sub 2} and C0{sub 2} produces differences between the hydrogen element mixture fraction ({xi}{sub H}) and the carbon element mixture fraction ({xi}{sub c}). The greatest effects occur on the rich side of stoichiometric, where {xi}{sub H} is observed to be smaller than {xi}{sub C} at all Reynolds numbers. Differential diffusion between H{sub 2} and H{sub 2}O creates a net flux of hydrogen element toward the stoichiometric contour and causes a local maximum in {xi}H that occurs near the stoichiometric condition. A differential diffusion variable {sup Z}H is defined as the difference between {xi}{sub H} and {xi}{sub C}. The variance Of {sup Z}H conditional on {xi}{sub C} also shows that differential diffusion effects are greatest on the rich side of the flame. Conditional variances of {sup Z}H are largest at intermediate Reynolds numbers.
Smith, L.L.; Dibble, R.W.; Talbot, L. [California Univ., Berkeley, CA (United States). Dept. of Mechanical Engineering; Barlow, R.S.; Carter, C.D. [Sandia National Labs., Livermore, CA (United States)
Measurements of fuel mixture fraction oscillations of a turbulent jet non-premixed flame
Science Conference Proceedings (OSTI)
This work describes new type of combustion instability for which the 3-way coupling between mixing, flame heat release, and acoustics is modified by local buoyancy effects. Measurements of fuel mixture fraction are made for a non-premixed jet flame in a combustion chamber to assess the dynamics of mixing under imposed acoustic oscillations (22-55 Hz). Infrared laser absorption and phase resolved acetone-planar laser induced fluorescence are used to measure the fuel mixture fraction and then the degree of fuel/air mixing is calculated by determining the unmixedness. Results show acoustic excitation causes oscillations in the degree of fuel/air mixing at the driving frequency, which results in oscillatory flame behavior. This oscillatory flame behavior couples to the buoyancy and this in turn affects the mixing. Results also show that the mixing becomes less effective when the excitation frequency is increased or when the flame is present, compared to the non-reacting case. This work describes a key coupling mechanism that occurs when buoyancy is a significant factor in the flow field. (author)
Kanga, D.M. [LG Chem Research Park, Dajeon 305-380 (Korea); Fernandez, V.; Culick, F.E.C. [Department of Mechanical Engineering, California Institute of Technology, Pasadena, CA 91125 (United States); Ratner, A. [Department of Mechanical and Industrial Engineering, University of Iowa, Iowa City, IA 52242 (United States)
Assessment of reduced mechanisms using One Dimensional Stochastic Turbulence model
turbulence model for a syngas jet flame. Proceeding of FallKerstein 2002), a turbulent syngas (CO/H2/NO) jet flame wasand DNS results of the syngas jet flame was recently done
Chien, Li-Chun
A numerical simulation of entrainment, turbulent advection, molecular import and chemical kinetics in a turbulent diffusion flame is used to investigate effects of molecular transport on turbulence-chemistry interactions. A fun finite-rate chemical mechanism is used to represent the combustion of a hydrogen-argon mixture issuing into air. Results based on incorporation of differential diffusion and variable Lewis number are compared to cases with the former effect, or both-effects, suppressed. Significant impact on radical species production and on NO emission index (based on a reduced mechanism for thermal NO) is found. A reduced mechanism for hydrogen-air combustion, omitting both effects and incorporating other simplifications, performs comparably except that its NO predictions agree well with the case of full chemistry and molecular transport, possibly due to cancellation of errors.
Menon, S.; Calhoon, W.H. Jr.; Goldin, G. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Aerospace Engineering; Kerstein, A.R. [Sandia National Labs., Livermore, CA (United States)
Improved understanding and control of high-speed jet interaction flows
A numerical study of the flow field generated by injection through diamondshaped orifices into a high-speed flow is presented in this document. Jet interaction flows have a wide range of applications in the field of engineering. These applications include the use of jets for fuel injection in scramjets, for reaction control of high-speed aerodynamic bodies and as cooling jets for skins of high-speed vehicles. A necessary requirement in the use of transverse jets for these and other applications is a thorough understanding of the physics of the interaction between the jet and freestream. This interaction generates numerous flow structures that include multiple shocks, vortices, recirculation regions and shear layers. This study involves diamond-shaped orifices that have the advantage of generating weaker or attached interaction shocks as compared to circular injectors. These injectors also negate the effects due to the recirculation region that is formed upstream of the injector. This study was undertaken in order to gain further understanding of the flow features generated by diamond-shaped injectors in a high-speed flow. Numerical simulations were performed using two different levels of turbulence models. Reynolds? Averaged Navier-Stokes (RANS) simulations were performed using the GASP flow solver while Detached-Eddy Simulation (DES) runs were performed using the Cobalt flow solver. A total of fifteen diamond injector simulations were performed using the RANS model for a 15 half-angle diamond injector. The fifteen simulations spanned over five different injection angles and three jet total pressures. In addition to these, two circular injector simulations were also performed. In addition, low pressure normal injection through diamond and circular orifices simulations were performed using DES. Results obtained from CFD were compared to available experimental data. The resulting flow structure and the turbulent properties of the flow were examined in detail. The normal injection case through the diamond-shaped orifice at the lowest jet total pressure was defined as the baseline case and is presented in detail. In order to study the effect of different components of the vorticity transport equation, an in-house code was used post-process the results from the RANS runs.
Srinivasan, Ravichandra
Effects of Micro- and Macroscale Turbulent Mixing on the Chemical Processes in Engine Exhaust Plumes
Science Conference Proceedings (OSTI)
Turbulent mixing and chemical reactions in the near field of an engine exhaust jet plume have been investigated using a mixing model that explicitly incorporates both large- and small-scale turbulent mixing and the molecular diffusion effects. A ...
S. Menon; J. Wu
Calculations of slurry pump jet impingement loads
This paper presents a methodology to calculate the impingement load in the region of a submerged turbulent jet where a potential core exits and the jet is not fully developed. The profile of the jet flow velocities is represented by a piece-wise linear function which satisfies the conservation of momentum flux of the jet flow. The adequacy of the of the predicted jet expansion is further verified by considering the continuity of the jet flow from the region of potential core to the fully developed region. The jet impingement load can be calculated either as a direct impingement force or a drag force using the jet velocity field determined by the methodology presented.
Wu, T.T.
On the Mechanism Underlying the Spontaneous Emergence of Barotropic Zonal Jets
Science Conference Proceedings (OSTI)
Zonal jets are commonly observed to spontaneously emerge in a ?-plane channel from a background of turbulence that is sustained in a statistical steady state by homogeneous stochastic excitation and dissipation of vorticity. The mechanism for jet ...
Nikolaos A. Bakas; Petros J. Ioannou
Jet Observables Without Jet Algorithms
We introduce a new class of event shapes to characterize the jet-like structure of an event. Like traditional event shapes, our observables are infrared/collinear safe and involve a sum over all hadrons in an event, but like a jet clustering algorithm, they incorporate a jet radius parameter and a transverse momentum cut. Three of the ubiquitous jet-based observables---jet multiplicity, summed scalar transverse momentum, and missing transverse momentum---have event shape counterparts that are closely correlated with their jet-based cousins. Due to their "local" computational structure, these jet-like event shapes could potentially be used for trigger-level event selection at the LHC. Intriguingly, the jet multiplicity event shape typically takes on non-integer values, highlighting the inherent ambiguity in defining jets. By inverting jet multiplicity, we show how to characterize the transverse momentum of the n-th hardest jet without actually finding the constituents of that jet. Since many physics applications do require knowledge about the jet constituents, we also build a hybrid event shape that incorporates (local) jet clustering information. As a straightforward application of our general technique, we derive an event-shape version of jet trimming, allowing event-wide jet grooming without explicit jet identification. Finally, we briefly mention possible applications of our method for jet substructure studies.
Daniele Bertolini; Tucker Chan; Jesse Thaler
Increasing jet entrainment, mixing and spreading
A free jet of air is disturbed at a frequency that substantially matches natural turbulences in the free jet to increase the entrainment, mixing, and spreading of air by the free jet, for example in a room or other enclosure. The disturbances are created by pulsing the flow of air that creates the free jet at the desired frequency. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct. 11 figs.
Farrington, R.B.
Increasing jet entrainment, mixing and spreading
A free jet of air is disturbed at a frequency that substantially matches natural turbulences in the free jet to increase the entrainment, mixing, and spreading of air by the free jet, for example in a room or other enclosure. The disturbances are created by pulsing the flow of air that creates the free jet at the desired frequency. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct.
Farrington, Robert B. (Wheatridge, CO)
A high efficiency, free electron laser is described utilizing a circular relativistic electron beam accelerator and a circular whispering mode optical waveguide for guiding optical energy in a circular path in the circular relativistic electron beam accelerator such that the circular relativistic electron beam and the optical energy are spatially contiguous in a resonant condition for free electron laser operation. Both a betatron and synchrotron are disclosed for use in the present invention. A free electron laser wiggler is disposed around the circular relativistic electron beam accelerator for generating a periodic magnetic field to transform energy from the circular relativistic electron beam to optical energy.
Brau, C.A.; Kurnit, N.A.; Cooper, R.K.
A high efficiency, free electron laser utilizing a circular relativistic electron beam accelerator and a circular whispering mode optical waveguide for guiding optical energy in a circular path in the circular relativistic electron beam accelerator such that the circular relativistic electron beam and the optical energy are spatially contiguous in a resonant condition for free electron laser operation. Both a betatron and synchrotron are disclosed for use in the present invention. A free electron laser wiggler is disposed around the circular relativistic electron beam accelerator for generating a periodic magnetic field to transform energy from the circular relativistic electron beam to optical energy.
Brau, Charles A. (Los Alamos, NM); Kurnit, Norman A. (Santa Fe, NM); Cooper, Richard K. (Los Alamos, NM)
Numerical modeling of interaction of a current with a circular cylinder near a rigid bed
Science Conference Proceedings (OSTI)
The numerical modeling of 2D turbulent flow around a smooth horizontal circular cylinder near a rigid bed with gap ratio G/D=0.3 at Reynolds number Re"D=9500 is investigated. Ansys^(R) 10.0-FLOTRAN program package is used to solve the governing equations ... Keywords: Circular cylinder, Numerical model, Particle image velocimetry, Steady flow, Strouhal number, Velocity field
M. Salih Kirkgoz; A. Alper Oner; M. Sami Akoz
PIV Studies of Large Scale Structures in the Near Field of Small Aspect Ratio Elliptic Jets
Science Conference Proceedings (OSTI)
The near flow field of small aspect ratio elliptic turbulent free jets (issuing from nozzle and orifice) was experimentally studied using a 2D PIV. Two point velocity correlations in these jets revealed the extent and orientation of the large scale structures ... Keywords: Axis switching, Elliptic jet, PIV, Spatial filtering, Two point correlation
G. Ramesh; L. Venkatakrishnan; A. Prabhu
A dichotomy in radio jet orientations
We examine the relative orientations of radio jets, central dust and stars in low-power (i.e., FR I and FR I/II) radio galaxies. We use the position angles of jet and dust to constrain the three-dimensional angle $\\theta_{\\rm DJ}$ between jet and dust. For galaxies with filamentary dust 'lanes' (which tend to be misaligned with the galaxy major axis) the jet is approximately perpendicular to the dust structure, while for galaxies with elliptical dust distributions (typically aligned with the galaxy major axis) there is a much wider distribution of $\\theta_{\\rm DJ}$. nThe dust ellipses are consistent with being nearly circular thin disks viewed at random viewing angles. The lanes are likely warped, unsettled dust structures. We consider two scenarios to explain the dust/jet orientation dichotomy.
Gijs Verdoes Kleijn; Tim de Zeeuw
Transilient Turbulence Theory. Part II: Turbulent Adjustment
Science Conference Proceedings (OSTI)
Turbulent adjustment is a scheme where dynamic instabilities in the flow are eliminated by turbulence. It is a form of first-order turbulence closure that is applicable to numerical forecast models of the atmosphere. The responsive form of ...
Roland B. Stull; Takehiko Hasegawa
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
EXECUTIVE OFFICE OF THE PRESIDENT EXECUTIVE OFFICE OF THE PRESIDENT OFFICE OF MANAGEMENT AND BUDGET WASHINGTON, DC 20503 May 29, 2003 CIRCULAR NO. A-76 (REVISED) TO THE HEADS OF EXECUTIVE DEPARTMENTS AND ESTABLISHMENTS SUBJECT: Performance of Commercial Activities 1. Purpose. This circular establishes federal policy for the competition of commercial activities. 2. Supersession. This circular supersedes Office of Management and Budget (OMB) Circular No. A-76 (Revised 1999), August 4, 1983; Circular No. A-76 Revised Supplemental Handbook (Revised 2000), March 1996; Office of Federal Procurement Policy Letter 92-1, "Inherently Governmental Functions," September 23, 1992; and OMB Transmittal Memoranda 1 through 25, Performance of Commercial Activities. 3. Authority. Reorganization Plan No. 2 of 1970 (31 U.S.C. § 1111); Executive Order 11541; the Office
Numerical Issues of Monte Carlo PDF for Large Eddy Simulations of Turbulent Flames
Carlo PDF Methods for Turbulent Diffusion Flames,� Combust.Flame 124:519-534 (2001). Muradoglu, M. , Jenny, P. Pope,Methane-Air Nonpremixed Jet Flames,� Combustion Science and
Bisetti, Fabrizio; Chen, J Y
Anomalous recovery of damped radial modes in a circular?sector duct with locally heated flow
Science Conference Proceedings (OSTI)
It is often desirable to predict acoustic propagation in a circular duct carrying a locally heated flow. Common examples include jet engines and certain industrial and commercial burners whose combustion?related noise can be an environmental problem if allowed to penetrate into the surroundings. In these cases axial gradients in the steady flow variables
J. R. Maham; S.?Y. Yeh
Science Conference Proceedings (OSTI)
A theory for quasigeostrophic turbulence in baroclinic jets is examined in which interaction between the mean flow and the perturbations is explicitly modeled by the nonnormal operator obtained by linearization about the mean flow, while the eddy�...
Timothy Delsole; Brian F. Farrell
TURBULENT FRBRNNING MVK130 Turbulent Combustion
TURBULENT F�?RBR�?NNING MVK130 Turbulent Combustion Poäng: 3.0 Betygskala: TH Valfri för: M4 to combustion, McGraw-Hill 1996. #12;
Measurement of Turbulent Flow Phenomena for the Lower Plenum of a Prismatic Gas-Cooled Reactor
Science Conference Proceedings (OSTI)
Mean velocity field and turbulence data are presented that measure turbulent flow phenomena in an approximately 1:7 scale model of a region of the lower plenum of a typical prismatic gas-cooled reactor (GCR) similar to a General Atomics design (Gas-Turbine-Modular Helium Reactor). The datawere obtained in the Matched-Index-of-Refraction (MIR) facility at Idaho National Laboratory (INL) and are offered as a benchmark for assessing computational fluid dynamics (CFD) software. This experiment has been selected as the first Standard Problem endorsed by the Generation IV International Forum. The primary objective of this paper is to document the experiment and present a sample of the data set that has been established for this standard problem. Present results concentrate on the region of the lower plenum near its far reflector wall (away from the outlet duct). The flowin the lower plenum consists of multiple jets injected into a confined crossflow�with obstructions. The model consists of a row of full circular posts along its centerline with half-posts on the two parallel walls to approximate flow scaled to that expected from the staggered parallel rows of posts in the reactor design. Posts, side walls and end walls are fabricated from clear, fused quartz to match the refractive index of the mineral oil working fluid so that optical techniques may be employed for the measurements. The benefit of the MIR technique is that it permits optical measurements to determine flow characteristics in complex passages and around objects to be obtained without locating intrusive transducers that will disturb the flow field and without distortion of the optical paths. An advantage of the INL system is its large size, leading to improved spatial and temporal resolution compared to similar facilities at smaller scales. A three-dimensional (3D) particle image velocimetry (PIV) system was used to collect the data. Inlet-jet Reynolds numbers (based on the hydraulic diameter of the jet and the timemean average flow rate) are approximately 4300 and 12,400. Uncertainty analysis and a discussion of the standard problem are included. The measurements reveal complicated flow patterns that include several large recirculation zones, reverse flow near the simulated reflector wall, recirculation zones in the upper portion of the plenum and complex flow patterns around the support posts. Data include three-dimensional PIV images of flow planes, data displays along the coordinate planes (slices) and presentations that describe the component flows at specific regions in the model.
Hugh M. McIlroy, Jr.; Donald M. McEligot; Robert J. Pink
Jet plume injection and combustion system for internal combustion engines
An improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure.
Oppenheim, Antoni K. (Kensington, CA); Maxson, James A. (Berkeley, CA); Hensinger, David M. (Albany, CA)
Jet plume injection and combustion system for internal combustion engines
This invention is comprised of an improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure.
Oppenheim, A.K.; Maxson, J.A.; Hensinger, D.M.
Jet plume injection and combustion system for internal combustion engines
An improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure. 24 figures.
Oppenheim, A.K.; Maxson, J.A.; Hensinger, D.M.
Control of flames by tangential jet actuators in oxy-fuel burners
Science Conference Proceedings (OSTI)
The active control of oxy-fuel flames from burners with separated jets is investigated. The control system consists of four small jet actuators, placed tangential to the exit of the main jets to generate a swirling flow. These actuators are able to modify the flow structure and to act on mixing between the reactants and consequently on the flame behavior. The burner (25 kW) is composed of separated jets, one jet of natural gas and one or two jets of pure oxygen. Experiments are conducted with three burner configurations, according to the number of jets, the jet exit velocities, and the separation distance between the jets. OH chemiluminescence measurements, particle image velocimetry, and measurements of NO{sub x} emissions are used to characterize the flow and the flame structure. Results show that the small jet actuators have a significant influence on the behavior of jets and the flame characteristics, particularly in the stabilization zone. It is shown that the control leads to a decrease in lift-off heights and to better stability of the flame. The use of jet actuators induces high jet spreading and an increase in turbulence intensity, which improves the mixing between the reactants and the surrounding fluid. Pollutant measurements show important results in terms of NO{sub x} reductions (up to 60%), in particular for low swirl intensity. The burner parameters, such as the number of jets and the spacing between the jets, also impact the flame behavior and NO{sub x} formation. (author)
Boushaki, Toufik [CORIA UMR 6614 CNRS-Universite et INSA de ROUEN, Site Universitaire du Madrillet, 76801 Saint Etienne du Rouvray, Cedex (France); Universite de Toulouse-INPT-UPS, IMFT (Institut de Mecanique des Fluides de Toulouse), Allee Camille Soula, F-31400 Toulouse, Cedex (France); Sautet, Jean-Charles [CORIA UMR 6614 CNRS-Universite et INSA de ROUEN, Site Universitaire du Madrillet, 76801 Saint Etienne du Rouvray, Cedex (France); Labegorre, Bernard [Air Liquide, Centre de Recherche Claude-Delorme, Les Loges-en-Josas, B.P. 126 78354 Jouy-en-Josas, Cedex (France)
Science Conference Proceedings (OSTI)
Evidence is presented which illustrates the role of jet stream-frontal zone clear air turbulence (CAT) as a mechanism for the exchange of air and chemical trace constituents between the stratosphere and the troposphere. Three-dimensional air ...
M. A. Shapiro
Turbulent Nonpremixed Flames (TNF): Experimental Data Archives and Computational Submodels
In the 1990s an international collaboration formed around a series of workshops that became known collectively as the International Workshop on Measurement and Computation of Turbulent Non-Premixed Flames (TNF). An online library, hosted by Sandia National Laboratory (California) was established that provides data sets and submodels or "mechanisms" for the study of turbulence-chemistry interactions in turbulent nonpremixed and partially premixed combustion. Data are organized by flame types: simple jet flames, piloted jet flames, bluff body flames, and swirl flames. These data sets provide a means for collaborative comparisons of both measured and simulated/modeled research results and also assist scientists in determining priorities for further research. More than 20 data sets or databases are available from this website, along with various downloadable files of chemical mechanisms. The website also provides an extensive bibliography and the proceedings of the workshops themselves from 1996 through 2012. Information continues to be added to this collection.
Federal Acquisition Circulars 17, 18 and 20 | Department of Energy
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
Acquisition Circulars 17, 18 and 20 Federal Acquisition Circulars 17, 18 and 20 Policy Flash 2007-61 Federal Acquisition Circulars 17, 18 and 20 More Documents & Publications...
We demonstrate the possibility of a turbulent flow of electrons in graphene in the hydrodynamic region, by calculating the corresponding turbulent probability density function. This is used to calculate the contribution of the turbulent flow to the conductivity within a quantum Boltzmann approach. The dependence of the conductivity on the system parameters arising from the turbulent flow is very different from that due to scattering.
Kumar S. Gupta; Siddhartha Sen
TURBULENT FRBRNNING MVK 130 Turbulent Combustion
TURBULENT F�?RBR�?NNING MVK 130 Turbulent Combustion Antal poäng: 3.0. Valfri för: M4. Kursansvarig program med hänsyn till de modeller som används. Litteratur S.R. Turns: An introduction to combustion, Mc
Quantum Gravity and Turbulence
We apply recent advances in quantum gravity to the problem of turbulence. Adopting the AdS/CFT approach we propose a string theory of turbulence that explains the Kolmogorov scaling in 3+1 dimensions and the Kraichnan and Kolmogorov scalings in 2+1 dimensions. In the gravitational context, turbulence is intimately related to the properties of spacetime, or quantum, foam.
Vishnu Jejjala; Djordje Minic; Y. Jack Ng; Chia-Hsiung Tze
Obfuscation (IND-CPA Security Circular Security)
Obfuscation (IND-CPA Security Circular Security) (Draft Version, 24 October 2013) firstname.lastname@example.com 2 Aarhus University, Denmark, email@example.com Abstract Circular security is an important notion for public-key encryption schemes and is needed by several cryptographic protocols. In circular security
International Association for Cryptologic Research (IACR)
Transient characteristics of C3H8/O2turbulent mixing in a hypersonic pulse detonation engine
Science Conference Proceedings (OSTI)
We present the results of a time-dependent three-dimensional numerical simulation of the turbulent mixing characteristics in the mixing chamber of a hypersonic pulse detonation engine (PDE). Fuel (C3H8) was injected through one supersonic injector, while ... Keywords: high altitude aircrafts, hypersonic propulsion, ionospheric flight, pulse detonation engine, supersonic jet, turbulent mixing
Khalid M. Saqr; Ahmed Faiz; Hassan Kassem; Mohsin Sies; Mazlan A. Wahid
Modeling Compressed Turbulence
Science Conference Proceedings (OSTI)
From ICE to ICF, the effect of mean compression or expansion is important for predicting the state of the turbulence. When developing combustion models, we would like to know the mix state of the reacting species. This involves density and concentration fluctuations. To date, research has focused on the effect of compression on the turbulent kinetic energy. The current work provides constraints to help development and calibration for models of species mixing effects in compressed turbulence. The Cambon, et al., re-scaling has been extended to buoyancy driven turbulence, including the fluctuating density, concentration, and temperature equations. The new scalings give us helpful constraints for developing and validating RANS turbulence models.
Israel, Daniel M. [Los Alamos National Laboratory
Kraichnan (1965) proposed that MHD turbulence occurs as a result of collisions between oppositely directed Alfv�n wave packets. Recent work has generated some controversy over the nature of non linear couplings between colliding Alfv�n waves. We find that the resolution to much of the confusion lies in the existence of a new type of turbulence, intermediate turbulence, in which the cascade of energy in the inertial range exhibits properties intermediate between those of weak and strong turbulent cascades. Some properties of intermediate MHD turbulence are: (i) in common with weak turbulent cascades, wave packets belonging to the inertial range are long lived; (ii) however, components of the strain tensor are so large that, similar to the situation in strong turbulence, perturbation theory is not applicable; (iii) the breakdown of perturbation theory results from the divergence of neighboring field lines due to wave packets whose perturbations in velocity and magnetic fields are localized, but whose perturba...
Goldreich, P
The Terascale High-Fidelity Simulations of Turbulent Combustion (TSTC) project is a multi-university collaborative effort to develop a high-fidelity turbulent reacting flow simulation capability utilizing terascale, massively parallel computer technology. The main paradigm of the approach is direct numerical simulation (DNS) featuring the highest temporal and spatial accuracy, allowing quantitative observations of the fine-scale physics found in turbulent reacting flows as well as providing a useful tool for development of sub-models needed in device-level simulations. Under this component of the TSTC program the simulation code named S3D, developed and shared with coworkers at Sandia National Laboratories, has been enhanced with new numerical algorithms and physical models to provide predictive capabilities for turbulent liquid fuel spray dynamics. Major accomplishments include improved fundamental understanding of mixing and auto-ignition in multi-phase turbulent reactant mixtures and turbulent fuel injection spray jets.
Rutland, Christopher J.
Radiosonde measurements of turbulence
NLE Websites -- All DOE Office Websites (Extended Search)
at Cranwell, Lincolnshire, W. H. Pick and G. A. Bull, 1926. 3 Talk structure * Geomagnetic sensors to measure orientation * Orientation variability as a turbulence measure *...
Spectral Wave�Turbulence Decomposition
Science Conference Proceedings (OSTI)
A new method of wave�turbulence decomposition is introduced, for which the only instrument required is one high-frequency pointwise velocity sensor. This is a spectral method that assumes equilibrium turbulence and no wave�turbulence interaction. ...
Jeremy D. Bricker; Stephen G. Monismith
Circular permutant GFP insertion folding reporters
Provided are methods of assaying and improving protein folding using circular permutants of fluorescent proteins, including circular permutants of GFP variants and combinations thereof. The invention further provides various nucleic acid molecules and vectors incorporating such nucleic acid molecules, comprising polynucleotides encoding fluorescent protein circular permutants derived from superfolder GFP, which polynucleotides include an internal cloning site into which a heterologous polynucleotide may be inserted in-frame with the circular permutant coding sequence, and which when expressed are capable of reporting on the degree to which a polypeptide encoded by such an inserted heterologous polynucleotide is correctly folded by correlation with the degree of fluorescence exhibited.
Waldo, Geoffrey S. (Santa Fe, NM); Cabantous, Stephanie (Los Alamos, NM)
Circular permutant GFP insertion folding reporters
Provided are methods of assaying and improving protein folding using circular permutants of fluorescent proteins, including circular permutants of GFP variants and combinations thereof. The invention further provides various nucleic acid molecules and vectors incorporating such nucleic acid molecules, comprising polynucleotides encoding fluorescent protein circular permutants derived from superfolder GFP, which polynucleotides include an internal cloning site into which a heterologous polynucleotide may be inserted in-frame with the circular permutant coding sequence, and which when expressed are capable of reporting on the degree to which a polypeptide encoded by such an inserted heterologous polynucleotide is correctly folded by correlation with the degree of fluorescence exhibited.
Waldo, Geoffrey S; Cabantous, Stephanie
Circular permutant GFP insertion folding reporters
Provided are methods of assaying and improving protein folding using circular permutants of fluorescent proteins, including circular permutants of GFP variants and combinations thereof. The invention further provides various nucleic acid molecules and vectors incorporating such nucleic acid molecules, comprising polynucleotides encoding fluorescent protein circular permutants derived from superfolder GFP, which polynucleotides include an internal cloning site into which a heterologous polynucleotide may be inserted in-frame with the circular permutant coding sequence, and which when expressed are capable of reporting on the degree to which a polypeptide encoded by such an inserted heterologous polynucleotide is correctly folded by correlation with the degree of fluorescence exhibited.
Waldo, Geoffrey S.; Cabantous, Stephanie
Fossil turbulence and fossil turbulence waves can be dangerous
Turbulence is defined as an eddy-like state of fluid motion where the inertial-vortex forces of the eddies are larger than any other forces that tend to damp the eddies out. By this definition, turbulence always cascades from small scales where vorticity is created to larger scales where turbulence fossilizes. Fossil turbulence is any perturbation in a hydrophysical field produced by turbulence that persists after the fluid is no longer turbulent at the scale of the perturbation. Fossil turbulence patterns and fossil turbulence waves preserve and propagate energy and information about previous turbulence. Ignorance of fossil turbulence properties can be dangerous. Examples include the Osama bin Laden helicopter crash and the Air France 447 Airbus crash, both unfairly blamed on the pilots. Observations support the proposed definitions, and suggest even direct numerical simulations of turbulence require caution.
Carl H Gibson
Hypervelocity impact jet formation
The hypervelocity impact of a particle on a surface generates a jet of shocked material which is thrown from the impact site. A simple analytic model has been developed to obtain expressions for the evolution of this jet of ejecta. The analysis is based on applying the conservation equations of mass and momentum to the problem of a normal impact of a sphere against a semi-infinite flat target. Expressions are developed for the evolution of the jet velocity, jet release point and the locus of points which describe the ejecta envelope. These analytical ejecta profiles are compared with high speed photographs of impact jet formation. 6 refs., 7 figs.
Ang, J.A.
Chemical turbulence equivalent to Nikolavskii turbulence
We find evidence that a certain class of reaction-diffusion systems can exhibit chemical turbulence equivalent to Nikolaevskii turbulence. The distinctive characteristic of this type of turbulence is that it results from the interaction of weakly stable long-wavelength modes and unstable short-wavelength modes. We indirectly study this class of reaction-diffusion systems by considering an extended complex Ginzburg-Landau (CGL) equation that was previously derived from this class of reaction-diffusion systems. First, we show numerically that the power spectrum of this CGL equation in a particular regime is qualitatively quite similar to that of the Nikolaevskii equation. Then, we demonstrate that the Nikolaevskii equation can in fact be obtained from this CGL equation through a phase reduction procedure applied in the neighborhood of a codimension-two Turing--Benjamin-Feir point.
Dan Tanaka
Four Lectures on Turbulent Combustion
Four Lectures on Turbulent Combustion N. Peters Institut f¨ur Technische Mechanik RWTH Aachen Turbulent Combustion: Introduction and Overview 1 1.1 Moment Methods in Modeling Turbulence with Combustion and Velocity Scales . . . . . . . . . . . 11 1.4 Regimes in Premixed Turbulent Combustion
Peters, Norbert
The first turbulent combustion
The first turbulent combustion arises in a hot big bang cosmological model Gibson (2004) where nonlinear exothermic turbulence permitted by quantum mechanics, general relativity, multidimensional superstring theory, and fluid mechanics cascades from Planck to strong force freeze out scales with gravity balancing turbulent inertial-vortex forces. Interactions between Planck scale spinning and non-spinning black holes produce high Reynolds number turbulence and temperature mixing with huge Reynolds stresses driving the rapid inflation of space. Kolmogorovian turbulent temperature patterns are fossilized as strong-force exponential inflation stretches them beyond the scale of causal connection ct where c is light speed and t is time. Fossil temperature turbulence patterns seed nucleosynthesis, and then hydro-gravitational structure formation in the plasma epoch, Gibson (1996, 2000). Evidence about formation mechanisms is preserved by cosmic microwave background temperature anisotropies. CMB spectra indicate hydro-gravitational fragmentation at supercluster to galaxy masses in the primordial plasma with space stretched by \\~10^50. Bershadskii and Sreenivasan (2002, 2003) CMB multi-scaling coefficients support a strong turbulence origin for the anisotropies prior to the plasma epoch.
Carl H. Gibson
Terascale Direct Numerical Simulations of Turbulent Combustion: Capabilities and Limits (PReSS Talk)
The rapid growth in computational capabilities has provided great opportunities for direct numerical simulations (DNS) of turbulent combustion, a type of simulations without any turbulence model. With the help of terascale high performance supercomputing (HPC) resources, we are now able to provide fundamental insight into turbulence-chemistry interaction in simple laboratory-scale turbulent flames with detailed chemistry using three-dimensional (3D) DNS. However, the actual domain size of 3D-DNS is still limited within {approx} O(10 cm{sup 3}) due to its tremendously high grid resolution required to resolve the smallest turbulent length scale as well as flame structures. Moreover, 3D-DNS will require more computing powers to investigate next-generation engines, of which operating conditions will be characterized by higher pressures, lower temperatures, and higher levels of dilution. In this talk, I will discuss the capabilities and limits of DNS of turbulent combustion and present some results of ignition/extinction characteristics of a highly diluted hydrogen flame counter-flowing against heated air. The results of our recent 3D-DNS of a spatially-developing turbulent lifted hydrogen jet flame in heated coflow will also be presented. The 3D-DNS was performed at a jet Reynolds number of 11,000 with {approx} 1 billion grid points, which required 3.5 million CPU hours on Cray XT3/XT4 at Oak Ridge National Laboratories.
Yoo, Chun Sang (Combustion Research Facility, SNL)
Policy Flash 2013-27 Federal Acquisition Circular (FAC) 2005...
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Policy Flash 2013-37 Federal Acquisition Circular (FAC) 2005...
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
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The invention discloses a new interface with non-circular conductance limit aperture(s) useful for effective transmission of non-circular ion beams between stages with different gas pressure. In particular, the invention provides an improved coupling of field asymmetric waveform ion mobility spectrometry (FAIMS) analyzers of planar or side-to-side geometry to downstream stages such as mass spectrometry or ion mobility spectrometry. In this case, the non-circular aperture is rectangular; other geometries may be optimum in other applications. In the preferred embodiment, the non-circular aperture interface is followed by an electrodynamic ion funnel that may focus wide ion beams of any shape into tight circular beams with virtually no losses. The jet disrupter element of the funnel may also have a non-circular geometry, matching the shape of arriving ion beam. The improved sensitivity of planar FAIMS/MS has been demonstrated in experiments using a non-contiguous elongated aperture but other embodiments (e.g., with a contiguous slit aperture) may be preferable, especially in conjunction with an ion funnel operated at high pressures.
Tang, Keqi (Richland, WA); Shvartsburg, Alexandre A. (Richland, WA); Smith, Richard D. (Richland, WA)
The ATLAS jet trigger system has a 3-level structure, and was designed based on the concept of Regions Of Interest, where only regions of the detector around interesting Level-1 objects are reconstructed at the higher levels. This philosophy has changed during 2011, and there now exists the possibility to unpacking the full calorimeter at Event Filter. In 2012, full calorimeter unpacking is also available at Level-2, in addition jet energies are now calibrated to jet energy scale, and cleaning cuts are applied to reduce rate spikes. This paper presents the performance of the jet trigger in 2011 and an overview of the new features available for 2012.
Tamsett, M; The ATLAS collaboration
ARM - Measurement - Atmospheric turbulence
NLE Websites -- All DOE Office Websites (Extended Search)
turbulence turbulence ARM Data Discovery Browse Data Comments? We would love to hear from you! Send us a note below or call us at 1-888-ARM-DATA. Send Measurement : Atmospheric turbulence High frequency velocity fluctuations that lead to turbulent transport of momentum, heat, mositure, and passive scalars, and often expressed in terms of variances and covariances. Categories Atmospheric State, Surface Properties Instruments The above measurement is considered scientifically relevant for the following instruments. Refer to the datastream (netcdf) file headers of each instrument for a list of all available measurements, including those recorded for diagnostic or quality assurance purposes. ARM Instruments CO2FLX : Carbon Dioxide Flux Measurement Systems ECOR : Eddy Correlation Flux Measurement System
Observations of Edge Turbulence
NLE Websites -- All DOE Office Websites (Extended Search)
Edge Turbulence Edge Turbulence near the X-point of Alcator C-Mod APS-2007 (1) J.L. Terry, S.J. Zweben*, B. LaBombard, I. Cziegler, O. Grulke + , D.P. Stotler* MIT - Plasma Science and Fusion Center *Princeton Plasma Physics Laboratory + MPI for Plasma Physics, EURATOM Assoc., Greifswald, Germany American Physical Society - Div. of Plasma Physics Orlando, FL Nov. 12 - Nov. 16, 2007 APS-2007 (2) Background and Motivation for "Xpt-region" View Strong edge turbulence has been observed in nearly all magnetic confinement devices. Desire predictive capability Most previous measurements made near outboard midplane where the turbulence has the following main features: - generation is ballooning-like (absent at inboard midplane, etc.) - filaments/blobs moves radially outward with some poloidal motion
A Baroclinic Model of turbulent dusty flows
The problem considered here is the numerical simulation of the turbulent dusty flow induced by explosions over soil surfaces. Some of the unresolved issues are: (1) how much dust is scoured from such surfaces; (2) where does the dust go in the boundary layer; (3) what is the dusty boundary layer height versus time; (4) what are the dusty boundary layer profiles; (5) how much of the dust mass becomes entrained into the dust stem; and (6) where does the dust go in the buoyant cloud? The author proposes a Baroclinic Model for flows with large density variations that actually calculates the turbulent mixing and transport of dust on an adaptive grid. The model is based on the following idealizations: (1) a loose dust bed; (2) an instantaneous shock fluidization of the dust layer; (3) the dust and air are in local equilibrium (so air viscosity enforces the no-slip condition); (4) the dust-air mixture is treated as a continuum dense fluid with zero viscosity; and (5) the turbulent mixing is dominated by baroclinically-generated vorticity. These assumptions lead to an inviscid set of conservation laws for the mixture, which are solved by means of a high-order Godunov algorithm for gasdynamics. Adaptive Mesh Refinement (AMR) is used to capture the turbulent mixing processes on the grid. One of the unique characteristics of these flows is that mixing occurs because vorticity is produced by an inviscid, baroclinic mechanism. A number of examples are presented to illustrate these baroclinic effects including shock interactions with dense-gas layers and dust beds, and dusty wall jets of airblast precursors. The conclusion of these studies is that dusty boundary layers grow because of mass entrainment from the fluidized bed (and not because of viscous wall drag) as proven by the Mass Integral Equation.
Kuhl, A.L.
Kraichnan (1965) proposed that MHD turbulence occurs as a result of collisions between oppositely directed Alfv\\'en wave packets. Recent work has generated some controversy over the nature of non linear couplings between colliding Alfv\\'en waves. We find that the resolution to much of the confusion lies in the existence of a new type of turbulence, intermediate turbulence, in which the cascade of energy in the inertial range exhibits properties intermediate between those of weak and strong turbulent cascades. Some properties of intermediate MHD turbulence are: (i) in common with weak turbulent cascades, wave packets belonging to the inertial range are long lived; (ii) however, components of the strain tensor are so large that, similar to the situation in strong turbulence, perturbation theory is not applicable; (iii) the breakdown of perturbation theory results from the divergence of neighboring field lines due to wave packets whose perturbations in velocity and magnetic fields are localized, but whose perturbations in displacement are not; (iv) 3--wave interactions dominate individual collisions between wave packets, but interactions of all orders $n\\geq 3$ make comparable contributions to the intermediate turbulent energy cascade; (v) successive collisions are correlated since wave packets are distorted as they follow diverging field lines; (vi) in common with the weak MHD cascade, there is no parallel cascade of energy, and the cascade to small perpendicular scales strengthens as it reaches higher wave numbers; (vii) For an appropriate weak excitation, there is a natural progression from a weak, through an intermediate, to a strong cascade.
P. Goldreich; S. Sridhar
Jet Mass Spectra in Higgs + One Jet at NNLL
The invariant mass of a jet is a benchmark variable describing the structure of jets at the LHC. We calculate the jet mass spectrum for Higgs plus one jet at the LHC at next-to-next-to-leading logarithmic (NNLL) order using a factorization formula. At this order, the cross section becomes sensitive to perturbation theory at the soft m_jet^2/p_T^jet scale. Our calculation is exclusive and uses the 1-jettiness global event shape to implement a veto on additional jets. The dominant dependence on the jet veto is removed by normalizing the spectrum, leaving residual dependence from non-global logarithms depending on the ratio of the jet mass and jet veto variables. For our exclusive jet cross section these non-global logarithms are parametrically smaller than in the inclusive case, allowing us to obtain a complete NNLL result. Results for the dependence of the jet mass spectrum on the kinematics, jet algorithm, and jet size R are given. Using individual partonic channels we illustrate the difference between the jet mass spectra for quark and gluon jets. We also study the effect of hadronization and underlying event on the jet mass in PYTHIA. To highlight the similarity of inclusive and exclusive jet mass spectra, a comparison to LHC data is presented.
Teppo T. Jouttenus; Iain W. Stewart; Frank J. Tackmann; Wouter J. Waalewijn
LES/PDF based modeling of sootturbulence interactions in turbulent flames
number density function. This LES/PDF approach is then used to simulate a turbulent natural gas jet strong correlation between the gas phase composition and soot moments. �? 2012 The Combustion Institute and the gas-phase composition are often neglected. In this case, the PDF is written as the product of the mar
Raman, Venkat
Response Relationship Between Juvenile Salmon and an Autonomous Sensor in Turbulent Flows
Science Conference Proceedings (OSTI)
Juvenile fall chinook salmon (Oncorhynchus tshawythscha) and an autonomous sensor device (Sensor Fish) were exposed to turbulent shear flows in order to determine how hydraulic conditions effected fish injury response. Studies were designed to establish correlation metrics between Sensor Fish device measurements and live fish injuries by conducting concurrent releases in a range of turbulent shear flows. Comparisons were made for two exposure scenarios. In the fast-fish-to-slow-water scenario, test fish were carried by the fast-moving water of a submerged turbulent jet and exposed into the standing water of a flume. In the slow-fish-to-fast-water scenario, test fish were introduced into a turbulent jet from standing water through an introduction tube placed just outside the edge of the jet. Motion-tracking analysis was performed on high-speed, high-resolution digital videos of all the releases at water jet velocities ranging from 3 to 22.9 m � s?1. Velocities of the Sensor Fish were very similar to those of live fish, but maximum accelerations of live fish were larger than those by Sensor Fish for all the nozzle velocities of both cenarios. A 10% probability of major injury threshold was found to occur at sensor fish accelerations of 513 and 260 (m � s?2) for the fast-fish-to-slow-water and slow-fish-to-fast-water scenarios, respectively. The findings provide a linkage between laboratory experiments of fish injury, field survival studies, and numerical modeling.
Richmond, Marshall C.; Deng, Zhiqun; McKinstry, Craig A.; Mueller, Robert P.; Carlson, Thomas J.; Dauble, Dennis D.
Science Conference Proceedings (OSTI)
Field observations of turbulent kinetic energy (TKE), dissipation rate ?, and turbulent length scale demonstrate the impact of both density stratification and nonlocal turbulent production on turbulent momentum flux. The data were collected in a ...
Malcolm E. Scully; W. Rocky Geyer; John H. Trowbridge
FastJet is a C++ package that provides a broad range of jet finding and analysis tools. It includes efficient native implementations of all widely used 2-to-1 sequential recombination jet algorithms for pp and e+e- collisions, as well as access to 3rd party jet algorithms through a plugin mechanism, including all currently used cone algorithms. FastJet also provides means to facilitate the manipulation of jet substructure, including some common boosted heavy-object taggers, as well as tools for estimation of pileup and underlying-event noise levels, determination of jet areas and subtraction or suppression of noise in jets.
Matteo Cacciari; Gavin P. Salam; Gregory Soyez
Effects of geometry on slot-jet film cooling performance
Physics of film cooling for shaped, inclined slot-jets with realistic slot-length-to-width ratios is studied for a range of blowing ratio and density ratio parameters typical of gas turbine operations. Effect of inlet and exit shaping of the slot-jet on both flow and thermal field is isolated, and the dominant mechanisms responsible for differences in these items are documented. A computation method was used to study 4 configurations. Field results and surface phenomena are presented. Both adiabatic film effectiveness and heat transfer coefficient are vital in assessing film cooling performance. Performance of two popular turbulence models were studied to evaluate ability to handle highly elliptic jet/crossflow interaction type processes. The simulations were consistent.
Hyams, D.G.; McGovern, K.T.; Leyiek, J.H. [Clemson Univ., SC (United States). Dept. of Mechanical Engineering
A spray-suppression model for turbulent combustion
A spray-suppression model that captures the effects of liquid suppressant on a turbulent combusting flow is developed and applied to a turbulent diffusion flame with water spray suppression. The spray submodel is based on a stochastic separated flow approach that accounts for the transport and evaporation of liquid droplets. Flame extinguishment is accounted for by using a perfectly stirred reactor (PSR) submodel of turbulent combustion. PSR pre-calculations of flame extinction times are determined using CHEMKIN and are compared to local turbulent time scales of the flow to determine if local flame extinguishment has occurred. The PSR flame extinguishment and spray submodels are incorporated into Sandia's flow fire simulation code, VULCAN, and cases are run for the water spray suppression studies of McCaffrey for turbulent hydrogen-air jet diffusion flames. Predictions of flame temperature decrease and suppression efficiency are compared to experimental data as a function of water mass loading using three assumed values of drop sizes. The results show that the suppression efficiency is highly dependent on the initial droplet size for a given mass loading. A predicted optimal suppression efficiency was observed for the smallest class of droplets while the larger drops show increasing suppression efficiency with increasing mass loading for the range of mass loadings considered. Qualitative agreement to the experiment of suppression efficiency is encouraging, however quantitative agreement is limited due to the uncertainties in the boundary conditions of the experimental data for the water spray.
A spray-suppression model for turbulent combustion
A spray-suppression model that captures the effects of liquid suppressant on a turbulent combusting flow is developed and applied to a turbulent diffusion flame with water spray suppression. The spray submodel is based on a stochastic separated flow approach that accounts for the transport and evaporation of liquid droplets. Flame extinguishment is accounted for by using a perfectly stirred reactor (PSR) submodel of turbulent combustion. PSR pre-calculations of flame extinction times are determined using CHEMKIN and are compared to local turbulent time scales of the flow to determine if local flame extinguishment has occurred. The PSR flame extinguishment and spray submodels are incorporated into Sandia's flow fire simulation code, VULCAN, and cases are run for the water spray suppression studies of McCaffrey for turbulent hydrogen-air jet diffusion flames. Predictions of flame temperature decrease and suppression efficiency are compared to experimental data as a function of water mass loading using three assumed values of drop sizes. The results show that the suppression efficiency is highly dependent on the initial droplet size for a given mass loading. A predicted optimal suppression efficiency was observed for the smallest class of droplets while the larger drops show increasing suppression efficiency with increasing mass loading for the range of mass loadings considered. Qualitative agreement to the experiment of suppression efficiency is encouraging, however quantitative agreement is limited due to the uncertainties in the boundary conditions of the experimental data for the water spray.
Recent results from jet production in deep inelastic ep scattering to investigate parton dynamics at low x are reviewed. The results on jet production in deep inelastic scattering and photoproduction used to test perturbative QCD are discussed and the values of alphas(Mz) extracted from a QCD analysis of the data are presented
C. Glasman
Numerical studies on the transient behaviour of a fire plume and ceiling jet
Science Conference Proceedings (OSTI)
Transient behaviour of a thermally induced fire plume and ceiling jet is predicted using the field modelling technique. In the field model, the k-@e model is used to simulate the turbulent air flow. The traditional wall-function approach is applied to ...
W.K Chow
On the Formation of Potential-Vorticity Anomalies in Upper-Level Jet-Front Systems
Science Conference Proceedings (OSTI)
We review and discuss a difference in interpretation of the role of turbulence in modifying the potential-vorticity distribution in the vicinity of upper-level jet-front systems. In the late 1970s, M. A. Shapiro presented observational evidence ...
Daniel Keyser; Richard Rotunno
A Theory of Baroclinic Turbulence
Science Conference Proceedings (OSTI)
Understanding the physical mechanism maintaining fluid turbulence remains a fundamental theoretical problem. The two-layer model is an analytically and computationally simple system in which the dynamics of turbulence can be conveniently studied; ...
Brian F. Farrell; Petros J. Ioannou
The Decay of Convective Turbulence
Science Conference Proceedings (OSTI)
Using simulations with a large-eddy model we have studied the decay of convective turbulence in the atmospheric boundary layer when the upward surface sensible heat flux is suddenly stopped. The decay of turbulent kinetic energy and temperature ...
F. T. M. Nieuwstadt; R. A. Brost
Statistical Predictability of Decaying Turbulence
Science Conference Proceedings (OSTI)
We use statistical models of turbulence with �eddy damping� (EDQNM) in order to study the problem of predictability of freely evolving two- and three-dimensional isotropic turbulent flows.
Olivier M�tais; Marcel Lesieur
Supersaturation Intermittency in Turbulent Clouds
Science Conference Proceedings (OSTI)
It is hypothesized that bursts of high supersaturation are produced in turbulent, convective clouds through interactions between cloud droplets and the small-scale structure of atmospheric turbulence. This hypothesis is based on the observation ...
Raymond A. Shaw
turbulence turbulence Dataset Summary Description This raw data reflects readings from instruments mounted on or near a 82 meter meteorological tower located at the National Wind Technology Center (NWTC), approximately 5 miles south of Boulder, CO (specifically: 39.9107 N, 105.2348 W, datum WGS84). Source NREL Date Released Unknown Date Updated Unknown Keywords DOE irradiance NREL NWTC temperature turbulence wind wind direction wind speed Data text/plain icon Raw data (txt, 82 KiB) application/vnd.openxmlformats-officedocument.spreadsheetml.sheet icon Raw data field descriptions (xlsx, 52.5 KiB) Quality Metrics Level of Review Some Review Comment Data have not been reviewed for accuracy or completeness; disclaimer available (http://www.nrel.gov/disclaimer.html). Temporal and Spatial Coverage
We observe that intergranular jets, originating in the intergranular space surrounding individual granules, tend to be associated with granular fragmentation, in particular, with the formation and evolution of a bright granular lane (BGL) within individual granules. The BGLs have recently been identified as vortex tubes by Steiner et al. We further discover the development of a well-defined bright grain located between the BGL and the dark intergranular lane to which it is connected. Signatures of a BGL may reach the lower chromosphere and can be detected in off-band H{alpha} images. Simulations also indicate that vortex tubes are frequently associated with small-scale magnetic fields. We speculate that the intergranular jets detected in the New Solar Telescope (NST) data may result from the interaction between the turbulent small-scale fields associated with the vortex tube and the larger-scale fields existing in the intergranular lanes. The intergranular jets are much smaller and weaker than all previously known jet-like events. At the same time, they appear much more numerous than the larger events, leading us to the speculation that the total energy release and mass transport by these tiny events may not be negligible in the energy and mass-flux balance near the temperature minimum atop the photosphere. The study is based on the photospheric TiO broadband (1.0 nm) filter data acquired with the 1.6 m NST operating at the Big Bear Solar Observatory. The data set also includes NST off-band H{alpha} images collected through a Zeiss Lyot filter with a passband of 0.025 nm.
Yurchyshyn, V. B.; Goode, P. R.; Abramenko, V. I. [Big Bear Solar Observatory, New Jersey Institute of Technology, Big Bear City, CA 92314 (United States); Steiner, O. [Kiepenheuer-Institut fuer Sonnenphysik, Schoeneckstrasse 6, D-79104 Freiburg (Germany)
We review up-to-date results on high-pt particles and jets in heavy ion collisions by three major LHC experiments, ALICE, ATLAS, and CMS. Results of analyses of 2010 and 2011 Pb+Pb data at $\\sqrt{s_{NN}} = 2.76$ TeV are discussed. We concentrate mainly on results by fully reconstructed jets and discuss similarities and important differences in measurements among experiments. We point to the importance of understanding the results in a view of difference between quark-initiated and gluon-initiated jets
Martin Spousta
We introduce a new class of jet algorithms designed to return conical jets with a variable Delta R radius. A specific example, in which Delta R scales as 1/pT, proves particularly useful in capturing the kinematic features of a wide variety of hard scattering processes. We implement this Delta R scaling in a sequential recombination algorithm and test it by reconstructing resonance masses and kinematic endpoints. These test cases show 10-20% improvements in signal efficiency compared to fixed Delta R algorithms. We also comment on cuts useful in reducing continuum jet backgrounds.
David Krohn; Jesse Thaler; Lian-Tao Wang
We introduce a jet shape observable defined for an ensemble of jets in terms of two-particle angular correlations and a resolution parameter R. This quantity is infrared and collinear safe and can be interpreted as a scaling exponent for the angular distribution of mass inside the jet. For small R it is close to the value 2 as a consequence of the approximately scale invariant QCD dynamics. For large R it is sensitive to non-perturbative effects. We describe the use of this correlation function for tests of QCD, for studying underlying event and pile-up effects, and for tuning Monte Carlo event generators.
Jankowiak, Martin; Larkoski, Andrew J.; /SLAC
Most gamma-ray bursts (GRBs) have erratic light curves, which demand that the GRB central engine launches an episodic outflow. Recent Fermi observations of some GRBs indicate a lack of the thermal photosphere component as predicted by the baryonic fireball model, which suggests a magnetic origin of GRBs. Given that powerful episodic jets have been observed along with continuous jets in other astrophysical black hole systems, here we propose an intrinsically episodic, magnetically dominated jet model for the GRB central engine. Accumulation and eruption of free magnetic energy in the corona of a differentially rotating, turbulent accretion flow around a hyperaccreting black hole lead to ejections of episodic, magnetically dominated plasma blobs. These blobs are accelerated magnetically, collide with each other at large radii, trigger rapid magnetic reconnection and turbulence, efficient particle acceleration, and radiation, and power the observed episodic prompt gamma-ray emission from GRBs.
Yuan Feng [Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Zhang Bing, E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States)
Federal Acquisition Circular 2005-60
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
Circular 2005-60 Circular 2005-60 SUMMARY: This document summarizes the Federal Acquisition Regulation (FAR) rules agreed to by the Civilian Agency Acquisition Council and the Defense Acquisition Regulations Council (Councils) in this Federal Acquisition Circular (FAC) 2005-60. Item Subject FAR Case I Reporting Executive Compensation and First-Tier Subcontract Awards 2008-039 II Payments Under Time-and- Materials and Labor-Hour Contracts 2011-003 III Extension of Sunset Date for Protests of Task and Delivery Orders 2012-007 IV DARPA-New Mexico Tax Agreement 2012-019 V Clarification of Standards for Computer Generation of Forms 2011-022 VI Technical Amendments Item I Reporting Executive Compensation and First-Tier Subcontract Awards (FAR Case
Circular symmetry in the Hitchin system
To study circularly symmetric field configurations in the SU(2) Hitchin system an SO(2) symmetry, [J_3, \\phi]=0 and [J_3, A_{\\pm}]=\\pm A_{\\pm}, is imposed on the Higgs scalar \\phi and the gauge fields A_{\\pm} of the system, respectively, where J_3 is a sum of the third components of the orbital angular momenta and the generators of the SU(2). The circular symmetry and the equation \\bar{D}\\phi=0 yield onstant, generally nonzero, vacuum expectation values for {\\rm Tr}(\\phi^{2}). The equation 4F_{z\\bar{z}}=[\\phi, \\phi^{*}] yields a system of differential equations which govern the circularly symmetric field configurations and an exact solution to these equations in a pure gauge form with nontrivial Higgs scalar is obtained.
Masaru Kamata
OMB Circular A-123, Appendix B
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
T H E D I R E C T O R January 15, 2009 CIRCULAR NO. A-123, Appendix B Revised TO THE HEADS OF EXECUTIVE DEPARTMENTS AND ESTABLISHMENTS SUBJECT: Improving the Management of Government Charge Card Programs Appendix B of OMB Circular A-123 prescribes policies and procedures to agencies regarding how to maintain internal controls that reduce the risk of fraud, waste, and error in government charge card programs. This revision responds to recommendations made by the Government Accountability Office (GAO) regarding the Federal purchase card program as well as agency comments and suggestions made by Agency/Organization Program Coordinators. These revisions replace and rescind all previously issued OMB Circular A-123 Appendix B policy dated February 2006 and August 2005. Significant updates to Appendix B are as follows:
Federal Acquisition Circular 2005-36
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
Federal Acquisition Circular 2005-36 Federal Acquisition Circular 2005-36 Item Subject FAR case I.............. Federal Technical Data Solution (FedTeDS) 2008-038 II............. Fair Labor Standards Act and Service Contract 2007-021 Act Price Adjustment Clauses. III............ New Designated Country-Taiwan 2009-014 IV............. Prohibition on Restricted Business Operations 2008-004 in Sudan and Imports from Burma. V.............. List of Approved Attorneys, Abstractors, and 2006-013 Title Companies. VI............. Cost Accounting Standards (CAS) 2007-002 Administration and Associated Federal Acquisition Regulation Clauses. VII............ Technical Amendments
Lattice Boltzmann equation simulations of turbulence, mixing, and combustion
We explore the capability of lattice Boltzmann equation (LBE) method for complex fluid flows involving turbulence, mixing, and reaction. In the first study, LBE schemes for binary scalar mixing and multi-component reacting flow with reactions are developed. Simulations of initially non-premixed mixtures yield scalar probability distribution functions that are in good agreement with numerical data obtained from Navier-Stokes (NS) equation based computation. One-dimensional chemically-reacting flow simulation of a premixed mixture yields a flame speed that is consistent with experimentally determined value. The second study involves direct numerical simulation (DNS) and large-eddy simulation (LES) of decaying homogenous isotropic turbulence (HIT) with and without frame rotation. Three categories of simulations are performed: (i) LBE-DNS in both inertial and rotating frames; (ii) LBE-LES in inertial frame; (iii) Comparison of the LBE-LES vs. NS-LES. The LBE-DNS results of the decay exponents for kinetic energy k and dissipation rate ?, and the low wave-number scaling of the energy spectrum agree well with established classical results. The LBE-DNS also captures rotating turbulence physics. The LBE-LES accurately captures low-wave number scaling, energy decay and large scale structures. The comparisons indicate that the LBE-LES simulations preserve flow structures somewhat more accurately than the NS-LES counterpart. In the third study, we numerically investigate the near-field mixing features in low aspect-ratio (AR) rectangular turbulent jets (RTJ) using the LBE method. We use D3Q19 multiple-relaxation-time (MRT) LBE incorporating a subgrid Smagorinsky model for LES. Simulations of four jets which characterized by AR, exit velocity, and Reynolds number are performed. The investigated near-field behaviors include: (1) Decay of mean streamwise velocity (MSV) and inverse MSV; (2) Spanwise and lateral profiles of MSV; (3) Half-velocity width development and MSV contours; and (4) Streamwise turbulence intensity distribution and spanwise profiles of streamwise turbulence intensity. The computations are compared against experimental data and the agreement is good. We capture both unique features of RTJ: the saddle-back spanwise profile of MSV and axis-switching of long axis from spanwise to lateral direction. Overall, this work serves to establish the feasibility of the LBE method as a viable tool for computing mixing, combustion, and turbulence.
Yu, Huidan
Particle-jet interactions in an MHD second stage combustor
An Argonne two-phase combustion flow computer code is used to simulate reacting flows to aid in the development of an advanced combustor for magnetohydrodynamic power generation. The combustion code is a general hydrodynamics computer code for two-phase, two- dimensional, steady state, turbulent, and reacting flows, based on mass, momentum, and energy conservation laws for multiple gas species and particles. The combustion code includes turbulence, integral combustion, and particle evaporation submodels. A recently developed integral combustion submodel makes calculations more efficient and more stable while still preserving the major physical effects of the complex combustion processes. The combustor under investigation is a magnetohydrodynamic second stage combustor in which opposed jets of oxidizer are injected into a confined cross-stream of hot coal gas flow following a first stage swirl combustor. The simulation is intended to enhance the understanding the of seed particle evaporation in the combustor and evaluate the effects of combustor operating conditions on seed particle evaporation and vapor dispersion, which directly affect overall magnetohydrodynamic power generation. Computation results show that oxidizer jet angle and particle size may greatly affect particle evaporation and vapor dispersion. At a jet angle about 130 degrees, particle evaporation rate is the highest because of the highest average gas temperature. As particle size increases beyond 10 microns in diameter, the effects of particle size on wall deposition rate, evaporation delay, and downstream seed vapor dispersion become more pronounced. 16 refs., 10 figs.
Lottes, S.A.; Chang, S.L.
Particle-jet interactions in an MHD second stage combustor
An Argonne two-phase combustion flow computer code is used to simulate reacting flows to aid in the development of an advanced combustor for magnetohydrodynamic power generation. The combustion code is a general hydrodynamics computer code for two-phase, two- dimensional, steady state, turbulent, and reacting flows, based on mass, momentum, and energy conservation laws for multiple gas species and particles. The combustion code includes turbulence, integral combustion, and particle evaporation submodels. A recently developed integral combustion submodel makes calculations more efficient and more stable while still preserving the major physical effects of the complex combustion processes. The combustor under investigation is a magnetohydrodynamic second stage combustor in which opposed jets of oxidizer are injected into a confined cross-stream of hot coal gas flow following a first stage swirl combustor. The simulation is intended to enhance the understanding the of seed particle evaporation in the combustor and evaluate the effects of combustor operating conditions on seed particle evaporation and vapor dispersion, which directly affect overall magnetohydrodynamic power generation. Computation results show that oxidizer jet angle and particle size may greatly affect particle evaporation and vapor dispersion. At a jet angle about 130 degrees, particle evaporation rate is the highest because of the highest average gas temperature. As particle size increases beyond 10 microns in diameter, the effects of particle size on wall deposition rate, evaporation delay, and downstream seed vapor dispersion become more pronounced. 16 refs., 10 figs.
Lottes, S.A.; Chang, S.L.
Science Conference Proceedings (OSTI)
Turbulence dynamo deals with the amplification of a seed magnetic field in a turbulent medium and has been studied mostly for uniform or spatially homogeneous seed magnetic fields. However, some astrophysical processes (e.g., jets from active galaxies, galactic winds, or ram-pressure stripping in galaxy clusters) can provide localized seed magnetic fields. In this paper, we numerically study amplification of localized seed magnetic fields in a turbulent medium. Throughout the paper, we assume that the driving scale of turbulence is comparable to the size of the system. Our findings are as follows. First, turbulence can amplify a localized seed magnetic field very efficiently. The growth rate of magnetic energy density is as high as that for a uniform seed magnetic field. This result implies that magnetic field ejected from an astrophysical object can be a viable source of a magnetic field in a cluster. Second, the localized seed magnetic field disperses and fills the whole system very fast. If turbulence in a system (e.g., a galaxy cluster or a filament) is driven at large scales, we expect that it takes a few large-eddy turnover times for the magnetic field to fill the whole system. Third, growth and turbulence diffusion of a localized seed magnetic field are also fast in high magnetic Prandtl number turbulence. Fourth, even in decaying turbulence, a localized seed magnetic field can ultimately fill the whole system. Although the dispersal rate of the magnetic field is not fast in purely decaying turbulence, it can be enhanced by an additional forcing.
Cho, Jungyeon; Yoo, Hyunju, E-mail: email@example.com [Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of)
On Why Disks Generate Magnetic Towers and Collimate Jets
We show that accretion disks with magnetic fields in them ought to make jets provided that their electrical conductivity prevents slippage and there is an ambient pressure in their surroundings. We study equilibria of highly wound magnetic structures. General Energy theorems demonstrate that they form tall magnetic towers whose height grows with every turn at a velocity related to the circular velocity in the accretion disk. The pinch effect amplifies the magnetic pressures toward the axis of the towers whose stability is briefly considered.
D Lynden-Bell
On Why Disks Generate Magnetic Towers and Collimate Jets
We show that accretion disks with magnetic fields in them ought to make jets provided that their electrical conductivity prevents slippage and there is an ambient pressure in their surroundings. We study equilibria of highly wound magnetic structures. General Energy theorems demonstrate that they form tall magnetic towers whose height grows with every turn at a velocity related to the circular velocity in the accretion disk. The pinch effect amplifies the magnetic pressures toward the axis of the towers whose stability is briefly considered.
Lynden-Bell, Donald
Policy Flash 2013-63 Federal Acquisition Circular (FAC) 2005...
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
3 Federal Acquisition Circular (FAC) 2005-67 Policy Flash 2013-63 Federal Acquisition Circular (FAC) 2005-67 Questions concerning this policy flash should be directed to Barbara...
Technical Standards, OMB Circular A-119 - May 14, 1998 | Department...
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
OMB Circular A-119 - May 14, 1998 Technical Standards, OMB Circular A-119 - May 14, 1998 May 14, 1998 Federal Participation in the Development and Use of Voluntary Consensus...
National Nuclear Security Administration (NNSA)
Turbulent Turbulent Flow with Implicit LES L.G. Margolin 1 Proceedings of the Joint Russian-American Five Laboratory Conference on Computational Mathematics/Physics 19-23 June, 2005 Vienna, Austria 1 Applied Physics Division, Los Alamos National Laboratory, Los Alamos, NM 87545, email@example.com 1 Abstract Implicit large eddy simulation (ILES) is a methodology for modeling high Reynolds' num- ber flows that combines computational efficiency and ease of implementation with predictive calculations and flexible application. Although ILES has been used for more than fifteen years, it is only recently that significant effort has gone into providing a physical rationale that speaks to its capabilities and its limitations. In this talk, we will present new theoret- ical results aimed toward building a justification and discuss some remaining gaps in our understanding and our practical
Reconnection is the process by which magnetic fields in a conducting fluid change their topology. This process is essential for understanding a wide variety of astrophysical processes, including stellar and galactic dynamos and astrophysical turbulence. To account for solar flares, solar cycles and the structure of the galactic magnetic field reconnection must be fast, propagating with a speed close to the Alfven speed. We show that the presence of a random magnetic field component substantially enhances the reconnection rate and enables fast reconnection, i.e. reconnection that does not depend on fluid resistivity. The enhancement of the reconnection rate is achieved via a combination of two effects. First of all, only small segments of magnetic field lines are subject to direct Ohmic annihilation. Thus the fraction of magnetic energy that goes directly into fluid heating goes to zero as fluid resistivity vanishes. However, the most important enhancement comes from the fact that unlike the laminar fluid case where reconnection is constrained to proceed line by line, the presence of turbulence enables many magnetic field lines to enter the reconnection zone simultaneously. A significant fraction of magnetic energy goes into MHD turbulence and this enhances reconnection rates through an increase in the field stochasticity. In this way magnetic reconnection becomes fast when field stochasticity is accounted for. As a consequence solar and galactic dynamos are also fast, i.e. do not depend on fluid resistivity.
A. Lazarian; E. Vishniac
Renormalized weak plasma turbulence theory
A renormalized Vlasov turbulence theory, derived by neglecting a mode coupling term in the Direct Interaction Approximation, is discussed. The theory reduces correctly to weak turbulence theory; it predicts both diffusion and polarization effects of the turbulent medium on test particles, as well as the inverse effects of the test particles on the medium. A heuristic, physical algorithm is presented for constructing the equations. The theory of the renormalized dielectric function is reviewed.
Krommes, J.A.; Kleva, R.G.
Jet Fuel from Microalgal Lipids
A fact sheet on production of jet fuel or multi-purpose military fuel from lipids produced by microalgae.
Not Available
Organic vapor jet printing system
An organic vapor jet printing system includes a pump for increasing the pressure of an organic flux.
Forrest, Stephen R
Simulation of turbulence in fireballs
The ALE technique is applied to the calculation of a small yield, low altitude nuclear explosion. When artificial diffusion effects caused by numerical errors are minimized, the fireball rises too rapidly, reaching an altitude in excess of that which is observed. This suggests that turbulent diffusion and entrainmert may be important. Hence, a turbulence model has been added to later calculations of the fireball dynamics. Some of the more important features of the calculational technique and the turbulence model are discussed. Preliminary results for a set of turbulence parameters and a particular low altitude fireball are presented. (auth)
Ruppel, H.M.; Gentry, R.A.; Daly, B.J.
Measurements of Enhanced Turbulent Mixing near Highways
Science Conference Proceedings (OSTI)
In August and September of 2010, measurements of turbulent fluxes and turbulent kinetic energy were made on highways in the Toronto area (Ontario, Canada). In situ turbulence measurements were made with a mobile laboratory while driving on the ...
Mark Gordon; Ralf M. Staebler; John Liggio; Paul Makar; Shao-Meng Li; Jeremy Wentzell; Gang Lu; Patrick Lee; Jeffrey R. Brook
Filtering Turbulent Sparsely Observed Geophysical Flows
Science Conference Proceedings (OSTI)
Filtering sparsely turbulent signals from nature is a central problem of contemporary data assimilation. Here, sparsely observed turbulent signals from nature are generated by solutions of two-layer quasigeostrophic models with turbulent cascades ...
John Harlim; Andrew J. Majda
Science Conference Proceedings (OSTI)
A two-dimensional (x-z) primitive equation model is used to study the interaction between a deep cold jet on a sloping bottom and the bottom boundary layer (BBL) of the deep ocean. Two closure schemes are used: a standard second order turbulence ...
Tal Ezer; Georges L. Weatherly
Analysis of a Radome Air-Motion System on a Twin-Jet Aircraft for Boundary-Layer Research
Science Conference Proceedings (OSTI)
A �radome gust probe� system was installed on a twin-jet aircraft for the purpose of boundary-layer research. This system provided a useful relatively low-cost method for air motion and turbulence measurements on an aircraft already equipped with ...
Michael Tjernstr�m; Carl A. Friehe
Circular, confined distribution for charged particle beams
A charged particle beam line is formed with magnetic optics that manipulate the charged particle beam to form the beam having a generally rectangular configuration to a circular beam cross-section having a uniform particle distribution at a predetermined location. First magnetic optics form a charged particle beam to a generally uniform particle distribution over a square planar area at a known first location. Second magnetic optics receive the charged particle beam with the generally square configuration and affect the charged particle beam to output the charged particle beam with a phase-space distribution effective to fold corner portions of the beam toward the core region of the beam. The beam forms a circular configuration having a generally uniform spatial particle distribution over a target area at a predetermined second location. 26 figs.
Garnett, R.W.; Dobelbower, M.C.
Circular, confined distribution for charged particle beams
A charged particle beam line is formed with magnetic optics that manipulate the charged particle beam to form the beam having a generally rectangular configuration to a circular beam cross-section having a uniform particle distribution at a predetermined location. First magnetic optics form a charged particle beam to a generally uniform particle distribution over a square planar area at a known first location. Second magnetic optics receive the charged particle beam with the generally square configuration and affect the charged particle beam to output the charged particle beam with a phase-space distribution effective to fold corner portions of the beam toward the core region of the beam. The beam forms a circular configuration having a generally uniform spatial particle distribution over a target area at a predetermined second location.
Garnett, Robert W. (Los Alamos, NM); Dobelbower, M. Christian (Toledo, OH)
Circular zig-zag scan video format
A circular, ziz-zag scan for use with vidicon tubes. A sine wave is generated, rectified and its fourth root extracted. The fourth root, and its inverse, are used to generate horizontal ramp and sync signals. The fourth root is also used to generate a vertical sync signal, and the vertical sync signal, along with the horizontal sync signal, are used to generate the vertical ramp signal. Cathode blanking and preamplifier clamp signals are also obtained from the vertical sync signal.
Peterson, C. Glen (Los Alamos, NM); Simmons, Charles M. (Los Alamos, NM)
Turbulent Combustion Properties of Premixed Syngases
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Turbulent Combustion Properties of Premixed Syngases Title Turbulent Combustion Properties of Premixed Syngases Publication Type Journal Article Year of Publication 2009 Authors...
Simulation of lean premixed turbulent combustion
turbulent methane combustion. Proc. Combust. Inst. , 29:in premixed turbulent combustion. Proc. Combust. Inst. ,for zero Mach number combustion. Combust. Sci. Technol. ,
Advanced Computational Methods for Turbulence and Combustion...
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Advanced Computational Methods for Turbulence and Combustion Advanced Computational Methods for Turbulence and Combustion Bell.png Key Challenges: Development and application of...
Supercomputers Capture Turbulence in the Solar Wind
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Supercomputers Capture Turbulence in the Solar Wind Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space...
Finite reaction rate effects and dilatation effects are explored using an extended laminar flamelet model and turbulence models including dilatation processes. For the H[sub 2]-air nonpremixed turbulent combustion experiment conducted by Evans et al. in a high-speed shear flow, the flamesheet model can reasonably predict the combustion region but fails to predict the profiles of mass fractions, especially for H[sub 2] near the jet axis and O[sub 2] close to the jet edge. The inclusion of both dilatation dissipation and pressure dilatation leads to no significant improvement of the simulation results in this relatively low Mach number test case. The results predicted by the laminar flamelet model dramatically improve the profiles of species mass fractions. This indicates that the high turbulent strain rate usually observed in high-speed flow has a significant influence on the turbulent combustion. The widely used assumptions, such as fast chemical reaction rate, and unity Prandtl and Lewis numbers, are not suitable for this high-speed turbulent flow. It is necessary to include effects of kinetic energy changes in the calculations. Numerical results also show that this supersonic nonpremixed turbulent combustion flow satisfies the criteria of the laminar flamelet model.
Zheng, L.L.; Bray, K.N.C. (Cambridge Univ. (United Kingdom). Dept. of Engineering)
Science Conference Proceedings (OSTI)
A vertically sheared eastward jet in the equatorial Pacific in late 1991 and early 1992 carried relatively fresh water from the western Pacific overriding the saltier surface layer of the central region. Salinity anomalies of about ?1.0 psu were ...
Dean Roemmich; Michele Morris; W. R. Young; J. R. Donguy
Revised OMB Circular A-76 (Revised November 14, 2002)
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
OMB Circular A-76 Revision Comments OMB Circular A-76 Revision Comments DRAFT OMB CIRCULAR A-76 (NOVEMBER 14, 2002) REVIEW COMMENTS AND RECOMMENDATIONS GENERAL COMMENTS: The Department of Energy (DOE) supports the overarching goal of OMB Circular A-76 that agencies should obtain "the best deal to the Taxpayer." We also support revisions to the Circular that "Keep the Process Moving" with the end result being: Faster/Cheaper Competitions; Improved Performance and Measures; Enhanced/Expanded Competition; Fairness; Realizing Significant Savings; and the Redirection of Resources to Mission Critical Requirements. Upon review of the draft Circular, the Department believes the proposed changes to Circular reflect a general improvement over the current version. The Department does, however, have
Stars form within molecular clouds but our understanding of this fundamental process remains hampered by the complexity of the physics that drives their evolution. We review our observational and theoretical knowledge of molecular clouds trying to confront the two approaches wherever possible. After a broad presentation of the cold interstellar medium and molecular clouds, we emphasize the dynamical processes with special focus to turbulence and its impact on cloud evolution. We then review our knowledge of the velocity, density and magnetic fields. We end by openings towards new chemistry models and the links between molecular cloud structure and star--formation rates.
Hennebelle, Patrick
Flow cytometer jet monitor system
A direct jet monitor illuminates the jet of a flow cytometer in a monitor wavelength band which is substantially separate from the substance wavelength band. When a laser is used to cause fluorescence of the substance, it may be appropriate to use an infrared source to illuminate the jet and thus optically monitor the conditions within the jet through a CCD camera or the like. This optical monitoring may be provided to some type of controller or feedback system which automatically changes either the horizontal location of the jet, the point at which droplet separation occurs, or some other condition within the jet in order to maintain optimum conditions. The direct jet monitor may be operated simultaneously with the substance property sensing and analysis system so that continuous monitoring may be achieved without interfering with the substance data gathering and may be configured so as to allow the front of the analysis or free fall area to be unobstructed during processing.
Van den Engh, Ger (Seattle, WA)
Magnetized Turbulent Dynamo in Protogalaxies
Science Conference Proceedings (OSTI)
The prevailing theory for the origin of cosmic magnetic fields is that they have been amplified to their present values by the turbulent dynamo inductive action in the protogalactic and galactic medium. Up to now, in calculation of the turbulent dynamo, it has been customary to assume that there is no back reaction of the magnetic field on the turbulence, as long as the magnetic energy is less than the turbulent kinetic energy. This assumption leads to the kinematic dynamo theory. However, the applicability of this theory to protogalaxies is rather limited. The reason is that in protogalaxies the temperature is very high, and the viscosity is dominated by magnetized ions. As the magnetic field strength grows in time, the ion cyclotron time becomes shorter than the ion collision time, and the plasma becomes strongly magnetized. As a result, the ion viscosity becomes the Braginskii viscosity. Thus, in protogalaxies the back reaction sets in much earlier, at field strengths much lower than those which correspond to field-turbulence energy equipartition, and the turbulent dynamo becomes what we call the magnetized turbulent dynamo. In this paper we lay the theoretical groundwork for the magnetized turbulent dynamo. In particular, we predict that the magnetic energy growth rate in the magnetized dynamo theory is up to ten times larger than that in the kinematic dynamo theory. We also briefly discuss how the Braginskii viscosity can aid the development of the inverse cascade of magnetic energy after the energy equipartition is reached.
Leonid Malyshkin; Russell M. Kulsrud
Advances in compressible turbulent mixing
Science Conference Proceedings (OSTI)
This volume includes some recent additions to original material prepared for the Princeton International Workshop on the Physics of Compressible Turbulent Mixing, held in 1988. Workshop participants were asked to emphasize the physics of the compressible mixing process rather than measurement techniques or computational methods. Actual experimental results and their meaning were given precedence over discussions of new diagnostic developments. Theoretical interpretations and understanding were stressed rather than the exposition of new analytical model developments or advances in numerical procedures. By design, compressibility influences on turbulent mixing were discussed--almost exclusively--from the perspective of supersonic flow field studies. The papers are arranged in three topical categories: Foundations, Vortical Domination, and Strongly Coupled Compressibility. The Foundations category is a collection of seminal studies that connect current study in compressible turbulent mixing with compressible, high-speed turbulent flow research that almost vanished about two decades ago. A number of contributions are included on flow instability initiation, evolution, and transition between the states of unstable flow onset through those descriptive of fully developed turbulence. The Vortical Domination category includes theoretical and experimental studies of coherent structures, vortex pairing, vortex-dynamics-influenced pressure focusing. In the Strongly Coupled Compressibility category the organizers included the high-speed turbulent flow investigations in which the interaction of shock waves could be considered an important source for production of new turbulence or for the enhancement of pre-existing turbulence. Individual papers are processed separately.
Dannevik, W.P.; Buckingham, A.C.; Leith, C.E. [eds.
Numerical simulation of jet mixing concepts in Tank 241-SY-101
The episodic gas release events (GRES) that have characterized the behavior of Tank 241-SY-101 for the past several years are thought to result from gases generated by the waste material in it that become trapped in the layer of settled solids at the bottom of the tank. Several concepts for mitigating the GREs have been proposed. One concept involves mobilizing the solid particles with mixing jets. The rationale behind this idea is to prevent formation of a consolidated layer of settled solids at the bottom of the tank, thus inhibiting the accumulation of gas bubbles in this layer. Numerical simulations were conducted using the TEMPEST computer code to assess the viability and effectiveness of the proposed jet discharge concepts and operating parameters. Before these parametric studies were commenced, a series of turbulent jet studies were conducted that established the adequacy of the TEMPEST code for this application. Configurations studied for Tank 241-SY-101 include centrally located downward discharging jets, draft tubes, and horizontal jets that are either stationary or rotating. Parameter studies included varying the jet discharge velocity, jet diameter, discharge elevation, and material properties. A total of 18 simulations were conducted and are reported in this document. The effect of gas bubbles on the mixing dynamics was not included within the scope of this study.
Trent, D.S.; Michener, T.E.
Measurements in film cooling flows: Hole L/D and turbulence intensity effects
Hot-wire anemometry of simulated film cooling was used to study the influence of freestream turbulence intensity and film cooling hole length-to-diameter ratio on mean velocity and turbulence intensity. Measurements were made in the zone where the coolant and freestream flows mix. Flow from one row of film cooling holes with a streamwise injection of 35{degree} and no lateral injection and with a coolant- to-freestream flow velocity ratio of 1.0 was investigated under freestream turbulence levels of 0.5 and 12%. Coolant-to-freestream density ratio was unity. Two length-to-diameter ratios for the film cooling holes, 2.3 and 7.0, are tested. Results show that under low freestream turbulence conditions, pronounced differences exist in the flowfield between L/D=7.0 and 2.3; the differences are less prominent at high freestream turbulence intensities. Generally, short-L/D injection results in ``jetting`` of the coolant further into the freestream flow and enhanced mixing. Other changes in the flowfield attributable to a rise in freestream turbulence intensity to engine- representative conditions are documented. 15 figs, 2 tabs, refs.
Burd, S.W.; Kaszeta, R.W.; Simon, T.W.
Boundary layer wind data observed by a Doppler lidar and sonic anemometers during the mornings of three intensive observational periods (IOP2, IOP3, and IOP7) of the Joint Urban 2003 (JU2003) field experiment are analyzed to extract the mean and turbulent characteristics of airflow over Oklahoma City, Oklahoma. A strong nocturnal low-level jet (LLJ) dominated the flow in the boundary layer over the measurement domain from midnight to the morning hours. Lidar scans through the LLJ taken after sunrise indicate that the LLJ elevation shows a gradual increase of 25-100 m over the urban area relative to that over the upstream suburban area. The mean wind speed beneath the jet over the urban area is about 10%-15% slower than that over the suburban area. Sonic anemometer observations combined with Doppler lidar observations in the urban and suburban areas are also analyzed to investigate the boundary layer turbulence production in the LLJ-dominated atmospheric boundary layer. The turbulence kinetic energy was higher over the urban domain mainly because of the shear production of building surfaces and building wakes. Direct transport of turbulent momentum flux from the LLJ to the urban street level was very small because of the relatively high elevation of the jet. However, since the LLJ dominated the mean wind in the boundary layer, the turbulence kinetic energy in the urban domain is correlated directly with the LLJ maximum speed and inversely with its height. The results indicate that the jet Richardson number is a reasonably good indicator for turbulent kinetic energy over the urban domain in the LLJ-dominated atmospheric boundary layer.
Wang, Yansen; Klipp, Cheryl L.; Garvey, Dennis M.; Ligon, David; Williamson, Chatt C.; Chang, Sam S.; Newsom, Rob K.; Calhoun, Ron
Circular zig-zag scan video format
This invention is comprised of a circular, zig-zag scan for use with vidicon tubes. A sine wave is generated, rectified and its fourth root extracted. The fourth root, and its inverse, are used to generate horizontal ramp and sync signals. The fourth root is also used to generate a vertical sync signal, and the vertical sync signal, along with the horizontal sync signal, are used to generate the vertical ramp signal. Cathode blanking and preamplifier clamp signals are also obtained from the vertical sync signal.
Peterson, C.G.; Simmons, C.M.
Circular zig-zag scan video format
A circular, ziz-zag scan for use with vidicon tubes is disclosed. A sine wave is generated, rectified and its fourth root extracted. The fourth root, and its inverse, are used to generate horizontal ramp and sync signals. The fourth root is also used to generate a vertical sync signal, and the vertical sync signal, along with the horizontal sync signal, are used to generate the vertical ramp signal. Cathode blanking and preamplifier clamp signals are also obtained from the vertical sync signal. 10 figs.
Peterson, C.G.; Simmons, C.M.
Acceleration of polarized protons in circular accelerators
The theory of depolarization in circular accelerators is presented. The spin equation is first expressed in terms of the particle orbit and then converted to the equivalent spinor equation. The spinor equation is then solved for three different situations: (1) a beam on a flat top near a resonance, (2) uniform acceleration through an isolated resonance, and (3) a model of a fast resonance jump. Finally, the depolarization coefficient, epsilon, is calculated in terms of properties of the particle orbit and the results are applied to a calculation of depolarization in the AGS.
Courant, E.D.; Ruth, R.D.
A Family of Circular Bargmann Transforms
When considering a charged particle evolving in the Poincar\\'e disk under influence of a uniform magnetic field with a strength proportional to +1, we construct for all hyperbolic Landau level \\epsilon^\\gamma_$m$ m = 4m(-m), m 2 Z+ \\[0, /2] a family of coherent states transforms labeled by (,m) and mapping isometrically square integrable functions on the unit circle with respect to the measure sin^\\gamma-2m (\\theta/2) d\\theta onto spaces of bound states of the particle. These transforms are called circular Bargmann transforms.
Zouhair Mouayn
On Collective Properties of Turbulent QED Plasma
Polarization properties of turbulent stochastically inhomogeneous ultrarelativistic QED plasma are studied. It is shown that the sign of nonlinear turbulent Landau damping corresponds to an instability of the spacelike modes and, for sufficiently large turbulent fields, to an actual instability of a system. Modification of plasmon dispersion relations due to turbulent effects are studied.
Martin Kirakosyan; Andrei Leonidov; Berndt Muller
This report details the progress of an effort to determine the quantitative aspects of the initiation of PBX 9502 (95% TATB, 5% Kel-F 800) by copper jets. The particular jet used was that produced by the LAW warhead (66-mm diameter, 42/sup 0/ angle cone, copper-lined, conical shaped charge). Fifteen experiments, in various configurations, have been fired to define the essential parameters for quantitatively measuring the jet performance and initiation of bare PBX 9502. 7 refs., 8 figs.
McAfee, J.M.
Photon plus jet production has been studied by the D0 experiment in Run II of the Fermilab Tevatron Collider at a centre of mass energy of sqrt{s}=1.96 TeV. Measurements of the inclusive photon, inclusive photon plus jet, photon plus heavy flavour jet cross sections and double parton interactions in photon plus three jet events are presented. They are based on integrated luminosities between 0.4 fb$^-1 and 1.0 fb^-1. The results are compared to perturbative QCD calculations in various approximations.
Lars Sonnenschein
Turbulence Regimes and Turbulence Intermittency in the Stable Boundary Layer during CASES-99
Science Conference Proceedings (OSTI)
An investigation of nocturnal intermittent turbulence during the Cooperative Atmosphere�Surface Exchange Study in 1999 (CASES-99) revealed three turbulence regimes at each observation height: 1) regime 1, a weak turbulence regime when the wind ...
Jielun Sun; Larry Mahrt; Robert M. Banta; Yelena L. Pichugina
Circular dichroism: A general theory based on quantum electrodynamics
Science Conference Proceedings (OSTI)
A theory of circular dichroism is developed through a direct calculation of the absorption rates for circularly polarized light on molecules. From this a differential rate as between left and right circularly polarized light is calculated. This is immediately related to the experimental data on circular dichroism. When the calculations are restricted to the dipole approximation we reproduce the rotatory strength in the form of a differential Einstein B coefficient. Higher moments are considered in detail and their effects analyzed for both the locked?in situation and the case of randomly oriented molecular absorbers. A general expression is obtained for the differential absorption rate.
E. A. Power; T. Thirunamachandran
Variability of Southern Ocean Jets Near Topography
Science Conference Proceedings (OSTI)
The interaction of jets with topography in the Southern Ocean is investigated using 19 years of altimetry data. In particular, the �jet jumping� mode of variability, by which two or more jets passing close to the same topographic feature show ...
Christopher C. Chapman; Rosemary Morrow
Predictability of Rotating Stratified Turbulence
Science Conference Proceedings (OSTI)
Although predictability represents one of the fundamental problems in atmospheric science, gaps in our knowledge remain. Theoretical understanding of the inverse error cascade is limited mostly to homogeneous, isotropic turbulence, whereas ...
K. Ngan; P. Bartello; D. N. Straub
Finescale Parameterizations of Turbulent Dissipation
Science Conference Proceedings (OSTI)
Fine- and microstructure data from a free fall profiler are analysed to test models that relate the turbulent dissipation rate (?) to characteristics of the internal wave field. The data were obtained from several distinct internal wave ...
Kurt L. Polzin; John M. Toole; Raymond W. Schmitt
Shroud for a submerged jet cutting nozzle
A shroud for a submerged jet cutting nozzle is described which separates the jet from surrounding fluid environment and enhances the cutting effect.
Schwab, Thomas L. (1369 Windsor Way, Livermore, CA 94550)
Direct Numerical Simulation of Autoiginition of a Hydrogen Jet in a
NLE Websites -- All DOE Office Websites (Extended Search)
Direct Numerical Simulation of Autoiginition of a Hydrogen Jet in a Direct Numerical Simulation of Autoiginition of a Hydrogen Jet in a Preheated Cross Flow Submitted by mkaczmar on June 4, 2013 - 13:52 Authors: Abdilghanie, A., Frouzakis, C.E., Fischer, P Autoignition of a nitrogen-diluted hydrogen mixture issuing from a round nozzle into a cross-flowing turbulent stream of preheated air flowing in a channel at a friction Reynolds number Re = 180 is inves- tigated via 3-D direct numerical simulations (DNS) at two crossflow stream temperatures (930 and 950 K). Three-dimensional visualizations of the JICF reveal a complicated flow structure characterized by a variety of coherent vortical structures resulting from the boundary layers near the walls and evolving from the jet instabilities. The mean pressure field set up by the flow
Federal Acquisition Regulation; Federal Acquisition Circular
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
2005-37; Introduction Federal Acquisition Circular (FAC) 2005-37 List of Rules in FAC 2005-37 Item Subject I. Registry of Disaster Response Contractors II. Limiting Length of Noncompetitive Contracts in "Unusual and Compelling Urgency" Circumstances III. GAO Access to Contractor Employees IV. Use of Commercial Services Item Authority V. Limitations on Pass-Through Charges VI. Award Fee Language Revision VII. National Response Framework VIII. Technical Amendments SUPPLEMENTARY INFORMATION: Summaries for each FAR rule follow. Item I-Registry of Disaster Response Contractors (FAR Case 2008-035) This interim rule amends the FAR at parts 2, 4, 7, 10, 13, 18, 26, and 52 to implement the Registry of Disaster Response Contractors provision, section 697 of the Department of
Federal Acquisition Circular WAC) 2001-24
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
FLASH 2004-20 July 12, 2004 Federal Acquisition Circular WAC) 2001-24 1. Incentives for Use of Performance-Based Contracting for Services (Interim) (FAR Case 2004-004) Effective Date: June 18, 2004 What is the purpose of this FAR Case? This interim rule amends the FAR providing authority to treat perfonnance-based contract or task orders for services as commercial items if specific conditions are met. It also requires agencies to report on perfonnance-based contracts or task orders awarded using this authority. This rulemaking affects FAR Parts 2, Definitions, 12, Acquisition of Commercial Items, 37, Service Contracting, and 52, Solicitation Provisions and Contract Clauses. ~ Provides that performance-based contracts and task orders for services with an estimated value not to exceed $25,000,000, be treated as
Federal Acquisition Regulation; Federal Acquisition Circular
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
0 0 Federal Acquisition Circular (FAC) 2005-40 Federal Register /Vol. 75, No. 55 /Tuesday, March 23, 2010 /page 14059 A summary for the FAR rule follows. Federal Awardee Performance and Integrity Information System (FAPIIS) (FAR case 2008-027) Effective Date: April 22, 2010. This final rule amends the FAR to implement section 872 of the Duncan Hunter National Defense Authorization Act for Fiscal Year 2009. Section 872 requires the establishment of a data system, Federal Awardee Performance and Integrity Information System (FAPIIS), containing specific information on the integrity and performance of covered Federal agency contractors and grantees. FAPIIS is available for use in award decisions at www.ppirs.gov. Government input to FAPIIS is accomplished at www.cpars.csd.disa.mil.
Turbulent flows and coherent structures emerging within turbulent flow fields have been extensively studied for the past few decades and a wide variety of experimental and numerical techniques have been developed for measurement and analysis of turbulent flows. The complex nature of turbulence requires methods that can accurately estimate its highly chaotic spatial and temporal behavior. Some of the classical cases of turbulent flows with simpler geometries have been well characterized by means of the existing experimental techniques and numerical models. Nevertheless, since most turbulent fields are of complex geometries; there is an increasing interest in the study of turbulent flows through models with more complicated geometries. In this dissertation, characteristics of turbulent flows through two different facilities with complex geometries are studied applying two different experimental methods. The first study involves the investigation of turbulent impinging jets through a staggered array of rods with or without crossflow. Such flows are crucial in various engineering disciplines. This experiment aimed at modeling the coolant flow behavior and mixing phenomena within the lower plenum of a Very High Temperature Reactor (VHTR). Dynamic Particle Image Velocimetry (PIV) and Matched Index of Refraction (MIR) techniques were applied to acquire the turbulent velocity fields within the model. Some key flow features that may significantly enhance the flow mixing within the test section or actively affect some of the structural components were identified in the velocity fields. The evolution of coherent structures within the flow field is further investigated using a Snapshot Proper Orthogonal Decomposition (POD) technique. Furthermore, a comparative POD method is proposed and successfully implemented for identification of the smaller but highly influential coherent structures which may not be captured in the full-field POD analysis. The second experimental study portrays the coolant flow through the core of an annular pebble bed VHTR. The complex geometry of the core and the highly turbulent nature of the coolant flow passing through the gaps of fuel pebbles make this case quite challenging. In this experiment, a high frequency Hot Wire Anemometry (HWA) system is applied for velocity measurements and investigation of the bypass flow phenomena within the near wall gaps of the core. The velocity profiles within the gaps verify the presence of an area of increased velocity close to the outer reflector wall; however, the characteristics of the coolant flow profile is highly dependent on the gap geometry and to a less extent on the Reynolds number of the flow. The time histories of the velocity are further analyzed using a Power Spectra Density (PSD) technique to acquire information about the energy content and energy transfer between eddies of different sizes at each point within the gaps.
Amini, Noushin
Interferometric Visualization of Jet Flames
Science Conference Proceedings (OSTI)
This paper presents visualizations of reacting, round jets of the premixed and nonpremixed type realized by using interferometry and, complementarily, direct photography. The available interferometer, proposed by Carlomagno (1986), employs low-cost components ... Keywords: coherent structures, combustion, destabilization, interferometry, jet flames
A. Stella; G. Guj; A. Mataloni
Flow-induced vibration of circular cylindrical structures
This report summarizes the flow-induced vibration of circular cylinders in quiescent fluid, axial flow, and crossflow, and applications of the analytical methods and experimental data in design evaluation of various system components consisting of circular cylinders. 219 figs., 30 tabs. (JDB)
Chen, S.S.
Jet quenching and heavy quarks
Jet quenching and more generally physics at high transverse momentum P_T scales is a cornerstone of the heavy-ion physics program at the LHC. In this work, the current understanding of jet quenching in terms of a QCD shower evolution being modified by the surrounding medium is reviewed along with the evidence for this picture from light parton high P_T observables. Conceptually, the same QCD shower description should also be relevant for heavy quarks, but with several important modifications introduced by the quark masses. Thus especially in the limit of small jet energy over quark mass E_jet/m_q, the relevant physics may be rather different from light quark jets, and several attempts to explain the observed phenomenology of heavy quarks at high P_T are discussed here.
Thorsten Renk
Complex Geometry Creation and Turbulent Conjugate Heat Transfer Modeling
Science Conference Proceedings (OSTI)
The multiphysics capabilities of COMSOL provide the necessary tools to simulate the turbulent thermal-fluid aspects of the High Flux Isotope Reactor (HFIR). Version 4.1, and later, of COMSOL provides three different turbulence models: the standard k-{var_epsilon} closure model, the low Reynolds number (LRN) k-{var_epsilon} model, and the Spalart-Allmaras model. The LRN meets the needs of the nominal HFIR thermal-hydraulic requirements for 2D and 3D simulations. COMSOL also has the capability to create complex geometries. The circular involute fuel plates used in the HFIR require the use of algebraic equations to generate an accurate geometrical representation in the simulation environment. The best-estimate simulation results show that the maximum fuel plate clad surface temperatures are lower than those predicted by the legacy thermal safety code used at HFIR by approximately 17 K. The best-estimate temperature distribution determined by COMSOL was then used to determine the necessary increase in the magnitude of the power density profile (PDP) to produce a similar clad surface temperature as compared to the legacy thermal safety code. It was determined and verified that a 19% power increase was sufficient to bring the two temperature profiles to relatively good agreement.
Bodey, Isaac T [ORNL; Arimilli, Rao V [ORNL; Freels, James D [ORNL
The Canopy Horizontal Array Turbulence Study
Science Conference Proceedings (OSTI)
The Canopy Horizontal Array Turbulence Study (CHATS) took place in spring 2007 and is the third in the series of Horizontal Array Turbulence Study (HATS) experiments. The HATS experiments have been instrumental in testing and developing subfilterscale (...
Edward G. Patton; Thomas W. Horst; Peter P. Sullivan; Donald H. Lenschow; Steven P. Oncley; William O. J. Brown; Sean P. Burns; Alex B. Guenther; Andreas Held; Thomas Karl; Shane D. Mayor; Luciana V. Rizzo; Scott M. Spuler; Jielun Sun; Andrew A. Turnipseed; Eugene J. Allwine; Steven L. Edburg; Brian K. Lamb; Roni Avissar; Ronald J. Calhoun; Jan Kleissl; William J. Massman; Kyaw Tha Paw U; Jeffrey C. Weil
Effects of Atmospheric Turbulence on Ballistic Testing
Science Conference Proceedings (OSTI)
The effects of atmospheric turbulence on munition target scatter are determined from numerical simulations of ballistic trajectories through many realizations of realistic simulated turbulent wind fields. A technique is evaluated for correcting ...
Rod Frehlich; Robert Sharman; Charles Clough; Michael Padovani; Kelly Fling; Ward Boughers; W. Scott Walton
Turbulent Mixing in Stably Stratified Shear Flows
Science Conference Proceedings (OSTI)
Vertical mixing of momentum and heat is investigated in turbulent stratified shear flows. It is assumed that the flow has uniform shear and stratification with homogeneous turbulence and that an equilibrium is reached between kinetic and ...
U. Schumann; T. Gerz
Dust Motions Driven by MHD Turbulence
We discuss the relative grain motions due to MHD turbulence in interstellar medium. It has been known for decades that turbulent drag is an efficient way to induce grain relative motions. However, earlier treatments disregarded magnetic field and used Kolmogorov turbulence. Unlike hydro turbulence, MHD turbulence is anisotropic on small scales. Moreover, compressible modes are important for MHD and magnetic perturbations can directly interact with grains. We provide calculations of grain relative motion for realistic interstellar turbulence driving that is consistent with the velocity dispersions observed in diffuse gas and for realistic grain charging. We account for the turbulence cutoff arising from abmipolar drag. Our results on grain shattering are consistent with the customary accepted cutoff size. We obtain grain velocities for turbulence with parameters consistent with those in HI and dark clouds. These velocities are smaller than those in earlier papers, where MHD effects were disregarded. Finally, w...
Lazarian, A; Yan, Huirong
Turbulent Kinetic Energy Budgets over Mountainous Terrain
Science Conference Proceedings (OSTI)
The objective of this study is to describe the characteristics of the airflow and turbulence structure over mountainous terrain. Turbulent characteristics of the airflow were measured using well-instrumented aircraft. The shear, buoyancy, ...
Theodore S. Karacostas; John D. Marwitz
Strong Turbulence in the Wave Crest Region
Science Conference Proceedings (OSTI)
High-resolution vertical velocity profiles in the surface layer of a lake reveal the turbulence structure beneath strongly forced waves. Dissipation rates of turbulence kinetic energy are estimated based on centered second-order structure ...
Johannes Gemmrich
Computation of turbulent recirculating flows using a hybrid adaptive grid
Science Conference Proceedings (OSTI)
A hybrid adaptive gridding procedure is applied to the computation of two-dimensional turbulent, recirculating flows. The procedure combines both the local refinement method and the global moving grid method. The moving grid method is applied to obtain the initial adaptive solution. The local refinement method is then used on the large error regions flagged by using the weight function approach. The test cases are a backward facing step flow, a two-dimensional side jet flow, and an axisymmetric swirling flow. By comparing with the fine uniform grid solution, the numerical efficiencies ranging from 20 to 40 are obtained in the test problems. The most attractive feature of the procedure is its ease of application.
Lee, D.; Yeh, C.L. (National Cheng Kung Univ., Tainan (Taiwan, Province of China). Inst. of Aeronautics and Astronautics)
A water cooled steam jet for transferring fluid and preventing vapor lock, or vaporization of the fluid being transferred, has a venturi nozzle and a cooling jacket. The venturi nozzle produces a high velocity flow which creates a vacuum to draw fluid from a source of fluid. The venturi nozzle has a converging section connected to a source of steam, a diffuser section attached to an outlet and a throat portion disposed therebetween. The cooling jacket surrounds the venturi nozzle and a suction tube through which the fluid is being drawn into the venturi nozzle. Coolant flows through the cooling jacket. The cooling jacket dissipates heat generated by the venturi nozzle to prevent vapor lock.
Wagner, Jr., Edward P. (Idaho Falls, ID)
Explains how jet fuel can be manufactured from propane and/or butane with attractive rates of return. This scheme is advantageous where large reserves of LPG-bearing gas is available or LPG is in excess. The following sequence of processes in involved: dehydrogenation of propane (and/or butane) to propylene (and/or butylene); polymerization of this monomer to a substantial yield of the desired polymer by recycling undesired polymer; and hydrotreating the polymer to saturate double bonds. An attribute of this process scheme is that each of the individual processes has been practiced commercially. The process should have appeal in those parts of the world which have large reserves of LPG-bearing natural gas but little or no crude oil, or where large excesses of LPG are available. Concludes that economic analysis shows attractive rates of return in a range of reasonable propane costs and product selling prices.
Maples, R.E.; Jones, J.R.
Science Conference Proceedings (OSTI)
In a typical coal-fired power station boiler the ignition and the combustion of the fuel is largely controlled by burner aerodynamics. An experimental and numerical study of the rectangular slot-burners widely used on power stations in Victoria, Australia has been conducted to improve understanding of jet development within the boiler. The 1:15 scale model burner consisted of a central (primary) rectangular fuel nozzle with two (secondary) rectangular air jets positioned above and below it. The burner jets entered the measurement vessel at an angle of 60 deg to the wall. A cross-flow jet was attached to the wall of the vessel to simulate the recirculation prevalent in power station boilers. Experiments were conducted using a primary to cross-flow jet velocity ratio ({phi}) of 1.0 and secondary to primary jet velocity ratios ({phi}) of 1.0 and 3.0. Laser Doppler Anemometry (LDA) was used to measure mean and turbulent velocity components in the near field and downstream regions of the jets. Cross-flow significantly influenced the near field flow development from the slot-burner by deviating both primary and secondary jets from their geometric axes towards the wall. The degree of deviation was greater for {phi} = 1.0 since the higher velocity secondary jets increased the overall momentum of the primary jet for {phi} = 3.0. A numerical investigation of the rectangular slot-burner was also performed. First, the numerical results were validated against the experimental results and then visualization of the developing flow field was used to reveal the finer details of the cross-flow/burner jet interaction. Agreement between numerical and experimental jet features was good, although the numerical results predicted a primary jet that was marginally too narrow. Also the predicted downstream behaviour for {phi} = 3.0 deviated more significantly from experimental observation. Using the SST turbulence model, the numerical results suggested that a twin vortex was generated behind the initial region of the primary jet and this would aid in mixing of gas and fuel between primary and secondary jets. (author)
Ahmed, S. [CSIRO Manufacturing and Materials Technology, Highett VIC-3190 (Australia); Hart, J.; Naser, J. [School of Engineering and Industrial Sciences, Swinburne University of Technology, Hawthorn VIC-3122 (Australia); Nikolov, J.; Solnordal, C.; Yang, W. [CSIRO Minerals, Clayton, VIC-3169 (Australia)
We present a detailed analysis of the orbit of Charon where we show its orbit to be circular. This analysis explores the effects of surface albedo variations on the astrometry and the resulting errors in the orbital elements. We present two new epochs of data from the Hubble Space Telescope taken in 2008 and 2010 and combine that with a re-analysis of previously published data from 1992 and 2002. Our adopted two-body Keplerian orbital elements for Charon are P = 6.3872273 {+-} 0.0000003 days, a = 19573 {+-} 2 km, e = 0., i = 96.218 {+-} 0.008 deg, L = 4.50177 {+-} 0.00018 rad, and {Omega} = 3.89249 {+-} 0.00012 rad for an epoch of JDT = 2452600.5 in the J2000 reference frame. The 1{sigma} upper limit to the eccentricity is 7.5 Multiplication-Sign 10{sup -5}. The predicted uncertainty in the position of Charon relative to Pluto at the time of the New Horizons encounter based on this orbit is 8 km.
Buie, Marc W. [Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302 (United States); Tholen, David J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Grundy, William M., E-mail: email@example.com, E-mail: email@example.com, E-mail: email@example.com [Lowell Observatory, 1400 W. Mars Hill Road, Flagstaff, AZ 86001 (United States)
Stimulated Neutrino Transformation Through Turbulence
We derive an analytical solution for the flavor evolution of a neutrino through a turbulent density profile which is found to accurately predict the amplitude and transition wavelength of numerical solutions on a case-by-case basis. The evolution is seen to strongly depend upon those Fourier modes in the turbulence which are approximately the same as the splitting between neutrino eigenvalues and, unexpectedly, we also find a dependence upon the long wavelength modes when the ratio of their amplitude and the wavenumber is of order, or greater than, the first root of the Bessel function $J_0$.
Kelly M. Patton; James P. Kneller; Gail C. McLaughlin
A spintronic source of circularly polarized single photons
We present a spintronic single photon source which emits circularly polarized light, where the helicity is determined by an applied magnetic field. Photons are emitted from an InGaAs quantum dot inside an electrically operated spin light-emitting diode, which comprises the diluted magnetic semiconductor ZnMnSe. The circular polarization degree of the emitted light is high, reaching 83% at an applied magnetic field of 2T and 96% at 6 T. Autocorrelation traces recorded in pulsed operation mode prove the emitted light to be antibunched. The two circular polarization states could be used for representing quantum states |0> and |1> in quantum cryptography implementations.
Asshoff, Pablo; Kalt, Heinz; Hetterich, Michael
A spintronic source of circularly polarized single photons
We present a spintronic single photon source which emits circularly polarized light, where the helicity is determined by an applied magnetic field. Photons are emitted from an InGaAs quantum dot inside an electrically operated spin light-emitting diode, which comprises the diluted magnetic semiconductor ZnMnSe. The circular polarization degree of the emitted light is high, reaching 83% at an applied magnetic field of 2T and 96% at 6 T. Autocorrelation traces recorded in pulsed operation mode prove the emitted light to be antibunched. The two circular polarization states could be used for representing quantum states |0> and |1> in quantum cryptography implementations.
Pablo Asshoff; Andreas Merz; Heinz Kalt; Michael Hetterich
Science Conference Proceedings (OSTI)
VNAP2 is a computer program for calculating turbulent (as well as laminar and inviscid), steady, and unsteady flow. VNAP2 solves the two-dimensional, time-dependent, compressible Navier-Stokes equations. The turbulence is modeled with either an algebraic mixing-length model, a one-equation model, or the Jones-Launder two-equation model. The geometry may be a single- or a dual-flowing stream. The interior grid points are computed using the unsplit MacCormack scheme. Two options to speed up the calculations for high Reynolds number flows are included. The boundary grid points are computed using a reference-plane-characteristic scheme with the viscous terms treated as source functions. An explicit artificial viscosity is included for shock computations. The fluid is assumed to be a perfect gas. The flow boundaries may be arbitrary curved solid walls, inflow/outflow boundaries, or free-jet envelopes. Typical problems that can be solved concern nozzles, inlets, jet-powered afterbodies, airfoils, and free-jet expansions. The accuracy and efficiency of the program are shown by calculations of several inviscid and turbulent flows. The program and its use are described completely, and six sample cases and a code listing are included.
Cline, M.C.
IAEA Information Circular 225 Revision 5: Fact Sheet | National Nuclear
National Nuclear Security Administration (NNSA)
IAEA Information Circular 225 Revision 5: Fact Sheet | National Nuclear IAEA Information Circular 225 Revision 5: Fact Sheet | National Nuclear Security Administration Our Mission Managing the Stockpile Preventing Proliferation Powering the Nuclear Navy Emergency Response Recapitalizing Our Infrastructure Continuing Management Reform Countering Nuclear Terrorism About Us Our Programs Our History Who We Are Our Leadership Our Locations Budget Our Operations Media Room Congressional Testimony Fact Sheets Newsletters Press Releases Speeches Events Social Media Video Gallery Photo Gallery NNSA Archive Federal Employment Apply for Our Jobs Our Jobs Working at NNSA Blog Home > Media Room > Fact Sheets > IAEA Information Circular 225 Revision 5: Fact Sheet Fact Sheet IAEA Information Circular 225 Revision 5: Fact Sheet Mar 23, 2012 The Department of Energy's National Nuclear Security Administration
Science Conference Proceedings (OSTI)
Circular dichroism and fluorescence polarization anisotropy are important tools for characterizing biomolecular systems. Both are used extensively in kinetic experiments involving stopped- or continuous flow systems as well as titrations and steady-state spectroscopy. This paper presents the theory for determining circular dichroism and fluorescence polarization anisotropy simultaneously, thus insuring the two parameters are recorded under exactly the same conditions and at exactly the same time in kinetic experiments. The approach to measuring circular dichroism is that used in almost all conventional dichrographs. Two arrangements for measuring fluorescence polarization anisotropy are described. One uses a single fluorescence detector and signal processing with a lock-in amplifier that is similar to the measurement of circular dichroism. The second approach uses classic ''T'' format detection optics, and thus can be used with conventional photon-counting detection electronics. Simple extensions permit the simultaneous measurement of the absorption and excitation intensity corrected fluorescence intensity.
Every 2-choosable graph is circular consecutive 2-choosable
, 2008 Abstract Suppose G is a graph, r is a positive real number and S(r) is a circle of perimeter r. For a positive real number t r, a (t, r)- circular consecutive colour-list assignment L is a mapping that assigns to each vertex v of G an interval L(v) of S(r) of length t. A circular L-colouring of G
Zhu, Xuding
An ignition device of the plasma jet type is disclosed. The device has a cylindrical cavity formed in insulating material with an electrode at one end. The other end of the cylindrical cavity is closed by a metal plate with a small orifice in the center which plate serves as a second electrode. An arc jumping between the first electrode and the orifice plate causes the formation of a highly-ionized plasma in the cavity which is ejected through the orifice into the engine cylinder area to ignite the main fuel mixture. Two improvements are disclosed to enhance the operation of the device and the length of the plasma plume. One improvement is a metal hydride ring which is inserted in the cavity next to the first electrode. During operation, the high temperature in the cavity and the highly excited nature of the plasma breaks down the metal hydride, liberating hydrogen which acts as an additional fuel to help plasma formation. A second improvement consists of a cavity insert containing a plurality of spaced, metal rings. The rings act as secondary spark gap electrodes reducing the voltage needed to maintain the initial arc in the cavity.
McIlwain, Michael E. (Franklin, MA); Grant, Jonathan F. (Wayland, MA); Golenko, Zsolt (North Reading, MA); Wittstein, Alan D. (Fairfield, CT)
Jet Performance and Jet Energy Scale Determination at CMS
Science Conference Proceedings (OSTI)
We describe the jet response of the CMS calorimeter which will be used to study pp collisions at Large Hadron Collider at CERN, Geneva, Switzerland at {radical}(s) = 14 TeV. The electromagnetic section of calorimeter consists of lead tungstate crystals which gives an excellent resolution for electrons. The hadron section is brass-scintillator sampling calorimeter read by wavelength shifting fibers in the central region (vertical bar {eta} vertical bar < 3.0) and steel/quartz-fibers in the forward (3.0 < vertical bar {eta} vertical bar < 5.0) region. Extensive test beam calibration data has been collected. A GEANT-based calorimeter simulation has been tuned to reproduce the test beam measurements. The calorimeter response to jets has been determined using this tuned simulation. We describe the calorimeter response to jets, the jet energy resolution, and the procedure we plan to use to establish the jet energy scale from a combination of test beam and pp data when we start taking data in September 2007.
Bhatti, Anwar A. [Experimental Physics Laboratory, The Rockefeller University, 1230 York Ave, New York NY 10021 (United States)
Coupled Mesoscale-Large-Eddy Modeling of Realistic Stable Boundary Layer Turbulence
Site-specific flow and turbulence information are needed for various practical applications, ranging from aerodynamic/aeroelastic modeling for wind turbine design to optical diffraction calculations. Even though highly desirable, collecting on-site meteorological measurements can be an expensive, time-consuming, and sometimes a challenging task. In this work, we propose a coupled mesoscale-large-eddy modeling framework to synthetically generate site-specific flow and turbulence data. The workhorses behind our framework are a state-of-the-art, open-source atmospheric model called the Weather Research and Forecasting (WRF) model and a tuning-free large-eddy simulation (LES) model. Using this coupled framework, we simulate a nighttime stable boundary layer (SBL) case from the well-known CASES-99 field campaign. One of the unique aspects of this work is the usage of a diverse range of observations for characterization and validation. The coupled models reproduce certain characteristics of observed low-level jets....
Wang, Yao; Manuel, Lance
Active control for turbulent premixed flame simulations
Science Conference Proceedings (OSTI)
Many turbulent premixed flames of practical interest are statistically stationary. They occur in combustors that have anchoring mechanisms to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. As a result, typical detailed simulations are performed in simplified model configurations such as decaying isotropic turbulence or inflowing turbulence. In these configurations, the turbulence seen by the flame either decays or, in the latter case, increases as the flame accelerates toward the turbulent inflow. This limits the duration of the eddy evolutions experienced by the flame at a given level of turbulent intensity, so that statistically valid observations cannot be made. In this paper, we apply a feedback control to computationally stabilize an otherwise unstable turbulent premixed flame in two dimensions. For the simulations, we specify turbulent in flow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm. We use the simulations to study the propagation and the local chemical variability of turbulent flame chemistry.
Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Lijewski, Michael J.
Dust Motions Driven by MHD Turbulence
We discuss the relative grain motions due to MHD turbulence in interstellar medium. It has been known for decades that turbulent drag is an efficient way to induce grain relative motions. However, earlier treatments disregarded magnetic field and used Kolmogorov turbulence. Unlike hydro turbulence, MHD turbulence is anisotropic on small scales. Moreover, compressible modes are important for MHD and magnetic perturbations can directly interact with grains. We provide calculations of grain relative motion for realistic interstellar turbulence driving that is consistent with the velocity dispersions observed in diffuse gas and for realistic grain charging. We account for the turbulence cutoff arising from abmipolar drag. Our results on grain shattering are consistent with the customary accepted cutoff size. We obtain grain velocities for turbulence with parameters consistent with those in HI and dark clouds. These velocities are smaller than those in earlier papers, where MHD effects were disregarded. Finally, we consider grain velocities arising from photoelectric emission, radiation pressure and the thrust due to molecular hydrogen formation. These are lower than relative velocities induced by turbulence. We conclude that turbulence should prevent these mechanisms from segregating grains by size.
A. Lazarian; Huirong Yan
Reflective ghost imaging through turbulence
Recent work has indicated that ghost imaging may have applications in standoff sensing. However, most theoretical work has addressed transmission-based ghost imaging. To be a viable remote-sensing system, the ghost imager needs to image rough-surfaced targets in reflection through long, turbulent optical paths. We develop, within a Gaussian-state framework, expressions for the spatial resolution, image contrast, and signal-to-noise ratio of such a system. We consider rough-surfaced targets that create fully developed speckle in their returns and Kolmogorov-spectrum turbulence that is uniformly distributed along all propagation paths. We address both classical and nonclassical optical sources, as well as a computational ghost imager.
Hardy, Nicholas D.; Shapiro, Jeffrey H. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
Fluid dynamics of bacterial turbulence
Self-sustained turbulent structures have been observed in a wide range of living fluids, yet no quantitative theory exists to explain their properties. We report experiments on active turbulence in highly concentrated 3D suspensions of Bacillus subtilis and compare them with a minimal fourth-order vector-field theory for incompressible bacterial dynamics. Velocimetry of bacteria and surrounding fluid, determined by imaging cells and tracking colloidal tracers, yields consistent results for velocity statistics and correlations over two orders of magnitude in kinetic energy, revealing a decrease of fluid memory with increasing swimming activity and linear scaling between energy and enstrophy. The best-fit model parameters allow for quantitative agreement with experimental data.
J�rn Dunkel; Sebastian Heidenreich; Knut Drescher; Henricus H. Wensink; Markus B�r; Raymond E. Goldstein
Eddy Formation in 2�-Layer, Quasigeostrophic Jets
Science Conference Proceedings (OSTI)
The formation of nonlinear eddies in unstable 2�-layer, quasigeostrophic jets is investigated using a piecewise constant potential vorticity, �contour dynamical� model. Both infinite and semi-infinite jet dynamics are explored, considering a ...
Ilson C. A. da Silveira; Glenn R. Flierl
BioJet Corporation | Open Energy Information
93940 Sector Carbon Product Monterey-based carbon credit developer and producer of bio-jet fuel derived from jatropha. References BioJet Corporation1 LinkedIn Connections...
Dynamics of the Southern Hemisphere Spiral Jet
Science Conference Proceedings (OSTI)
The formation of the Southern Hemisphere spiral jet is investigated using observations over a 40-yr period. It is found that between late March and early April, the upper-tropospheric westerly jet in the Southern Hemisphere undergoes a transition ...
Lindsey N. Williams; Sukyoung Lee; Seok-Woo Son
African Easterly Jet: Structure and Maintenance
Science Conference Proceedings (OSTI)
This article investigates the African easterly jet (AEJ), its structure, and the forcings contributing to its maintenance, critically revisiting previous work that attributed the maintenance of the jet to soil moisture gradients over tropical ...
Man-Li C. Wu; Oreste Reale; Siegfried D. Schubert; Max J. Suarez; Randy D. Koster; Philip J. Pegion
Science Conference Proceedings (OSTI)
The convection heat transfer characteristics of supercritical CO{sub 2} in a vertical circular tube of 2 mm inner diameter were investigated experimentally for pressures ranging from 78 to 95 bar, inlet temperatures from 25 to 40 C, and inlet Reynolds numbers from 3800 to 20,000. The effects of the heat flux, thermo-physical properties, buoyancy and thermal acceleration on the convection heat transfer were analyzed. The experimental results show that for high inlet Reynolds numbers (e.g. Re = 9000) and high heat fluxes, a significant local deterioration and recovery of the heat transfer was found for upward flows but not for downward flows. Comparison of the experimental data for inlet Reynolds numbers from 3800 to 20,000 with some well-known empirical correlations showed large differences especially when the heat transfer deteriorates and then recovers when the effect of buoyancy is significant. The experimental data was used to develop modified local turbulent Nusselt number correlations for supercritical CO{sub 2} flowing in vertical small circular tubes. (author)
Li, Zhi-Hui; Jiang, Pei-Xue; Zhao, Chen-Ru; Zhang, Yu. [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China)
Physical Processes of Interstellar Turbulence
I discuss the role of self-gravity and radiative heating and cooling in shaping the nature of the turbulence in the interstellar medium (ISM) of our galaxy. The heating and cooling cause it to be highly compressible, and, in some regimes of density and temperature, to become thermally unstable, tending to spontaneously segregate into warm/diffuse and cold/dense phases. On the other hand, turbulence is an inherently mixing process, tending to replenish the density and temperature ranges that would be forbidden under thermal processes alone. The turbulence in the ionized ISM appears to be transonic (i.e, with Mach numbers $\\Ms \\sim 1$), and thus to behave essentially incompressibly. However, in the neutral medium, thermal instability causes the sound speed of the gas to fluctuate by up to factors of $\\sim 30$, and thus the flow can be highly supersonic with respect to the dense/cold gas, although numerical simulations suggest that this behavior corresponds more to the ensemble of cold clumps than to the clumps' internal velocity dispersion. Finally, coherent large-scale compressions in the warm neutral medium (induced by, say, the passage of spiral arms or by supernova shock waves) can produce large, dense molecular clouds that are subject to their own self-gravity, and begin to contract gravitationally. Because they are populated by nonlinear density fluctuations, whose local free-fall times are significantly smaller than that of the whole cloud, the fluctuations terminate their collapse earlier, giving rise to a regime of hierarchical gravitational fragmentation, with small-scale collapses occurring within larger-scale ones. Thus, the "turbulence" in molecular clouds may be dominated by a gravitationally contracting component at all scales.
Enrique Vazquez-Semadeni
Advanced thermally stable jet fuels
Science Conference Proceedings (OSTI)
The Pennsylvania State University program in advanced thermally stable coal-based jet fuels has five broad objectives: (1) Development of mechanisms of degradation and solids formation; (2) Quantitative measurement of growth of sub-micrometer and micrometer-sized particles suspended in fuels during thermal stressing; (3) Characterization of carbonaceous deposits by various instrumental and microscopic methods; (4) Elucidation of the role of additives in retarding the formation of carbonaceous solids; (5) Assessment of the potential of production of high yields of cycloalkanes by direct liquefaction of coal. Future high-Mach aircraft will place severe thermal demands on jet fuels, requiring the development of novel, hybrid fuel mixtures capable of withstanding temperatures in the range of 400--500 C. In the new aircraft, jet fuel will serve as both an energy source and a heat sink for cooling the airframe, engine, and system components. The ultimate development of such advanced fuels requires a thorough understanding of the thermal decomposition behavior of jet fuels under supercritical conditions. Considering that jet fuels consist of hundreds of compounds, this task must begin with a study of the thermal degradation behavior of select model compounds under supercritical conditions. The research performed by The Pennsylvania State University was focused on five major tasks that reflect the objectives stated above: Task 1: Investigation of the Quantitative Degradation of Fuels; Task 2: Investigation of Incipient Deposition; Task 3: Characterization of Solid Gums, Sediments, and Carbonaceous Deposits; Task 4: Coal-Based Fuel Stabilization Studies; and Task 5: Exploratory Studies on the Direct Conversion of Coal to High Quality Jet Fuels. The major findings of each of these tasks are presented in this executive summary. A description of the sub-tasks performed under each of these tasks and the findings of those studies are provided in the remainder of this volume (Sections 1 through 5).
Schobert, H.H.
Physical Processes of Interstellar Turbulence
I discuss the role of self-gravity and radiative heating and cooling in shaping the nature of the turbulence in the interstellar medium (ISM) of our galaxy. The heating and cooling cause it to be highly compressible, and, in some regimes of density and temperature, to become thermally unstable, tending to spontaneously segregate into warm/diffuse and cold/dense phases. On the other hand, turbulence is an inherently mixing process, tending to replenish the density and temperature ranges that would be forbidden under thermal processes alone. The turbulence in the ionized ISM appears to be transonic (i.e, with Mach numbers $\\Ms \\sim 1$), and thus to behave essentially incompressibly. However, in the neutral medium, thermal instability causes the sound speed of the gas to fluctuate by up to factors of $\\sim 30$, and thus the flow can be highly supersonic with respect to the dense/cold gas, although numerical simulations suggest that this behavior corresponds more to the ensemble of cold clumps than to the clumps'...
Vazquez-Semadeni, Enrique
Science Conference Proceedings (OSTI)
Turbulent dynamo phenomena, observed almost everywhere in astrophysical objects and also in the laboratory in the recent VKS2 experiment, are investigated using a shell model technique to describe magnetohydrodynamic turbulence. Detailed numerical simulations at very high Rossby numbers ({alpha}{sup 2} dynamo) show that as the magnetic Reynolds number increases, the dynamo action starts working and different regimes are observed. The model, which displays different large-scale coherent behaviors corresponding to different regimes, is able to reproduce the magnetic field reversals observed both in a geomagnetic dynamo and in the VKS2 experiment. While rough quantitative estimates of typical times associated with the reversal phenomenon are consistent with paleomagnetic data, the analysis of the transition from oscillating intermittent through reversal and finally to stationary behavior shows that the nature of the reversals we observe is typical of {alpha}{sup 2} dynamos and completely different from VKS2 reversals. Finally, the model shows that coherent behaviors can also be naturally generated inside the many-mode dynamical chaotic model, which reproduces the complexity of fluid turbulence, as described by the shell technique.
Perrone, D.; Nigro, G.; Veltri, P. [Universita della Calabria, Dipartimento di Fisica and Centro Nazionale Interuniversitario Struttura della Materia, Unita di Cosenza, I-87030 Arcavacata di Rende (Italy)
Probability Densities in Strong Turbulence
According to modern developments in turbulence theory, the "dissipation" scales (u.v. cut-offs) $\\eta$ form a random field related to velocity increments $\\delta_{\\eta}u$. In this work we, using Mellin's transform combined with the Gaussain large -scale boundary condition, calculate probability densities (PDFs) of velocity increments $P(\\delta_{r}u,r)$ and the PDF of the dissipation scales $Q(\\eta, Re)$, where $Re$ is the large-scale Reynolds number. The resulting expressions strongly deviate from the Log-normal PDF $P_{L}(\\delta_{r}u,r)$ often quoted in the literature. It is shown that the probability density of the small-scale velocity fluctuations includes information about the large (integral) scale dynamics which is responsible for deviation of $P(\\delta_{r}u,r)$ from $P_{L}(\\delta_{r}u,r)$. A framework for evaluation of the PDFs of various turbulence characteristics involving spatial derivatives is developed. The exact relation, free of spurious Logarithms recently discussed in Frisch et al (J. Fluid Mech. {\\bf 542}, 97 (2005)), for the multifractal probability density of velocity increments, not based on the steepest descent evaluation of the integrals is obtained and the calculated function $D(h)$ is close to experimental data. A novel derivation (Polyakov, 2005), of a well-known result of the multi-fractal theory [Frisch, "Turbulence. {\\it Legacy of A.N.Kolmogorov}", Cambridge University Press, 1995)), based on the concepts described in this paper, is also presented.
Victor Yakhot
Quantifying Turbulence for Tidal Power Applications
Using newly collected data from a tidal power site in Puget Sound, WA, metrics for turbulence quantification are assessed and discussed. The quality of raw ping Acoustic Doppler Current Profiler (ADCP) data for turbulence studies is evaluated against Acoustic Doppler Velocimeter (ADV) data at a point. Removal of Doppler noise from the raw ping data is shown to be a crucial step in turbulence quantification. Excluding periods of slack tide, the turbulent intensity estimates at a height of 4.6 m above the seabed are 8% and 11% from the ADCP and ADV, respectively. Estimates of the turbulent dissipation rate are more variable, from 10e-3 to 10e-1 W/m^3. An example analysis of coherent Turbulent Kinetic Energy (TKE) is presented.
Thomson, Jim; Richmond, Marshall C.; Polagye, Brian; Durgesh, Vibhav
Jet physics at HERA, Tevatron and LHC
In this short report, we discuss the Jet Physics results and perspectives at HERA, Tevatron and LHC.
C. Royon
Inclusive jet production at the Tevatron
Preliminary results on inclusive jet production in proton-antiproton collisions at {radical}s = 1.96 TeV based on 1 fb{sup -1} of CDF Run II data are presented. Measurements are preformed using different jet algorithms in a wide range of jet transverse momentum and jet rapidity. The measured cross sections are compared to next-to-leading order perturbative QCD calculations
Norniella, Olga; /Barcelona, IFAE
Shaping Planetary Nebulae by Jets
We conduct 2D axisymmetrical hydrodynamical simulations to investigate the interaction of a collimated fast wind (CFW; wide jets) with a spherical AGB wind. The code includes radiative cooling. We find that the shape of the planetary nebula (PN) is sensitive to the exact mass loss history of the AGB wind, and the opening angle of the CFW. Some typical PN morphologies are obtained, but many other observed morphologies seem to require more ingredients than what we assume in our present simulations, e.g., equatorial AGB wind, and ionization and fast wind during the PN phase. The hot bipolar bubble formed by the jets is an X-ray source.
Muhammad Akashi
Inclusive jet production at Tevatron
Science Conference Proceedings (OSTI)
The CDF and D0 Collaborations have measured the inclusive jet cross section using 1992--93 collider data at {radical}s = 1,800 GeV. The D0 measurement is higher than NLO QCD predictions, though within systematic uncertainties. The CDF measurement is in very good agreement with NLO QCD predictions for transverse energies (E{sub T}) below 200 GeV. However it is systemically higher than NLO QCD predictions for E{sub T} above 200 GeV. The CDF measurement of two-jet mass and total transverse energy spectra also show a similar excess above QCD predictions at higher E{sub T}.
Bhatti, A.A.; CDF Collaboration; D0 Collaboration
Production of biocomponent containing jet fuels
Science Conference Proceedings (OSTI)
Recent demands for low aromatic content jet fuels have shown significant increase in the last 20 years. This was generated by the growing of aviation. Further than quality requirements were more aggravated in front of jet fuels. This was generated by ... Keywords: aromatic content, biocomponent, crystallization point, jet fuel, kerosene, vegetable oil
Z. Eller; P. Solymosi; T. Kasza; Z. Varga; J. Hancs�k
Science Conference Proceedings (OSTI)
Direct numerical simulations of 2D temporally-evolving luminous turbulent ethylene-air jet diffusion flames are performed using a high-order compressible Navier-Stokes solver. The simulations use a reduced mechanism derived from a detailed ethylene-air chemical kinetic mechanism that includes the reaction pathways for the formation of polycyclic aromatic hydrocarbons. The gas-phase chemistry is coupled with a detailed soot particle model based on the method of moments with interpolative closure that accounts for soot nucleation, coagulation, surface growth through HACA mechanism, and oxidation. Radiative heat transfer of CO{sub 2}, H{sub 2}O, and soot is treated by solving the radiative transfer equation using the discrete transfer method. This work presents preliminary results of radiation effects on soot dynamics at the tip of a jet diffusion flame with a particular focus on soot formation/oxidation.
Sankaran, Ramanan [ORNL
Experimental investigation of over-expanded supersonic steam jet submerged in quiescent water
Science Conference Proceedings (OSTI)
This study was designed to determine the behaviour of an over-expanded supersonic steam jet in quiescent water. Only two shapes of steam plume were observed and an analytical model was constructed. The axial and radial temperature distributions were measured in the steam plume and in the surrounding water. The flow pattern and temperature distributions were influenced mainly by steam mass flux and water temperature. The results confirmed the occurrence of compression and expansion waves in the steam plume, and indicated that the temperature distributions reflected the steam plume shapes. The axial temperature distributions in the forepart of the steam plume were independent of water temperature. Empirical correlations were found that predicted the dimensionless axial and radial temperatures of the turbulent jet region. Moreover, prediction of the steam plume length by the dimensionless axial temperature showed good agreement with the experimental results. (author)
Wu, Xin-Zhuang; Yan, Jun-Jie; Li, Wen-Jun; Pan, Dong-Dong; Liu, Guang-Yao [State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an 710049 (China)
Visualizing the unseen forces of turbulence
NLE Websites -- All DOE Office Websites (Extended Search)
Grasping the vast power of turbulence could help researchers design better weather forecasts, more efficient cars, quieter helicopters and even faster ships that "float" through...
Supercomputers Capture Turbulence in the Solar Wind
NLE Websites -- All DOE Office Websites (Extended Search)
Provide Web Site Feedback: email@example.com Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space...
Characteristics of Langmuir Turbulence in the Ocean Mixed Layer
Science Conference Proceedings (OSTI)
This study uses large-eddy simulation (LES) to investigate the characteristics of Langmuir turbulence through the turbulent kinetic energy (TKE) budget. Based on an analysis of the TKE budget a velocity scale for Langmuir turbulence is proposed. ...
Alan L. M. Grant; Stephen E. Belcher
Kinetic Energy Transfer between Internal Gravity Waves and Turbulence
Science Conference Proceedings (OSTI)
We describe a reliable method for distinguishing the mean, wave and turbulence fields when internal waves with changing amplitude perturb the turbulent boundary layer. By integrating the component wave and turbulence kinetic energy budgets ...
J. J. Finnigan
Science Conference Proceedings (OSTI)
This paper presents a turbulence closure for neutral and stratified atmospheric conditions. The closure is based on the concept of the total turbulent energy. The total turbulent energy is the sum of the turbulent kinetic energy and turbulent ...
Thorsten Mauritsen; Gunilla Svensson; Sergej S. Zilitinkevich; Igor Esau; Leif Enger; Branko Grisogono
The turbulence encountered by a point on a rotating wind turbine blade has characteristics that in some important respects are different from those measured by a stationary anemometer. The conventional one-peaked continuous spectrum becomes, broadly, a two-peaked spectrum that in addition contains a set of narrow-band spikes of turbulence energy, one centered on the frequency of rotor rotation and the others centered on multiples of that frequency. The rotational sampling effect on wind spectra is quantified using measurements of wind velocity by anemometers on stationary crosswind circular arrays. Characteristics of fluctuating wind are compared to measured fluctuations of bending moments of the rotor blades and power output fluctuations of a horizontal-axis wind turbine at the same site. The wind characteristics and the correlations between wind fluctuations and wind turbine fluctuations provide a basis for improving turbine design, siting, and control. 6 refs., 11 figs., 1 tab.
Connell, J.R.; George, R.L.
Electromagnetic weak turbulence theory revisited
The statistical mechanical reformulation of weak turbulence theory for unmagnetized plasmas including fully electromagnetic effects was carried out by Yoon [Phys. Plasmas 13, 022302 (2006)]. However, the wave kinetic equation for the transverse wave ignores the nonlinear three-wave interaction that involves two transverse waves and a Langmuir wave, the incoherent analogue of the so-called Raman scattering process, which may account for the third and higher-harmonic plasma emissions. The present paper extends the previous formalism by including such a term.
Yoon, P. H. [IPST, University of Maryland, College Park, Maryland 20742 (United States); Ziebell, L. F. [Instituto de Fisica, UFRGS, Porto Alegre, RS (Brazil); Gaelzer, R.; Pavan, J. [Instituto de Fisica e Matematica, UFPel, Pelotas, RS (Brazil)
Fifteen Lectures on Laminar and Turbulent Combustion
Fifteen Lectures on Laminar and Turbulent Combustion N. Peters RWTH Aachen Ercoftac Summer School in Combustion Systems 1 Lecture 2: Calculation of Adiabatic Flame Temperatures and Chemical Equilibria 20: Laminar Diffusion Flames: Different Flow Geometries 156 Lecture 11: Turbulent Combustion: Introduction
Peters, Norbert
The Turbulence Structure of Nocturnal Slope Flow
Science Conference Proceedings (OSTI)
Measurements of the turbulence structure of nocturnal slope flow are used to test the hypothesis that slope flow turbulence in the region above the low-level wind maximum is decoupled from the surface and has a local structure similar to that ...
T. W. Horst; J. C. Doran
A Quadratic Closure for Compressible Turbulence
Science Conference Proceedings (OSTI)
We have investigated a one-point closure model for compressible turbulence based on third- and higher order cumulant discard for systems undergoing rapid deformation, such as might occur downstream of a shock or other discontinuity. In so doing, we find the lowest order contributions of turbulence to the mean flow, which lead to criteria for Adaptive Mesh Refinement. Rapid distortion theory (RDT) as originally applied by Herring closes the turbulence hierarchy of moment equations by discarding third order and higher cumulants. This is similar to the fourth-order cumulant discard hypothesis of Millionshchikov, except that the Millionshchikov hypothesis was taken to apply to incompressible homogeneous isotropic turbulence generally, whereas RDT is applied only to fluids undergoing a distortion that is 'rapid' in the sense that the interaction of the mean flow with the turbulence overwhelms the interaction of the turbulence with itself. It is also similar to Gaussian closure, in which both second and fourth-order cumulants are retained. Motivated by RDT, we develop a quadratic one-point closure for rapidly distorting compressible turbulence, without regard to homogeneity or isotropy, and make contact with two equation turbulence models, especially the K-{var_epsilon} and K-L models, and with linear instability growth. In the end, we arrive at criteria for Adaptive Mesh Refinement in Finite Volume simulations.
Futterman, J A
Window Function for Non-Circular Beam CMB Anisotropy Experiment
We develop computationally rapid methods to compute the window function for a cosmic microwave background anisotropy experiment with a non-circular beam which scans over large angles on the sky. To concretely illustrate these methods we compute the window function for the Python V experiment which scans over large angles on the sky with an elliptical Gaussian beam.
Tarun Souradeep; Bharat Ratra
On the longest increasing subsequence of a circular list
Science Conference Proceedings (OSTI)
The longest increasing circular subsequence (LICS) of a list is considered. A Monte Carlo algorithm to compute it is given which has worst case execution time O(n^3^/^2logn) and storage requirement O(n). It is proved that the expected length @m(n) of ... Keywords: Combinatorial problems, Randomized algorithms
M. H. Albert; M. D. Atkinson; Doron Nussbaum; J�rg-R�diger Sack; Nicola Santoro
Using circular programs to deforest in accumulating parameters
Science Conference Proceedings (OSTI)
Functional languages allow a modular programming style by function composition, which however can lead to inefficient runtime behavior due to production and consumption of intermediate results.We present a new mechanizable transformation technique for ... Keywords: accumulating parameters, circular programs, deforestation, intermediate data structures, lazy composition, lazy evaluation, multiple traversals, program transformation, tupling
Janis Voigtl�nder
Spectrum of gravitational radiation from primordial turbulence
Science Conference Proceedings (OSTI)
Energy injection into the early universe can induce turbulent motions of the primordial plasma, which in turn act as a source for gravitational radiation. Earlier work computed the amplitude and characteristic frequency of the relic gravitational wave background, as a function of the total energy injected and the stirring scale of the turbulence. This paper computes the frequency spectrum of relic gravitational radiation from a turbulent source of the stationary Kolmogoroff form which acts for a given duration, making no other approximations. We also show that the limit of long source wavelengths, commonly employed in aeroacoustic problems, is an excellent approximation. The gravitational waves from cosmological turbulence around the electroweak energy scale will be detectable by future space-based laser interferometers for a substantial range of turbulence parameters.
Gogoberidze, Grigol [Centre for Plasma Astrophysics, K.U. Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); National Abastumani Astrophysical Observatory, 2A Kazbegi Ave, GE-0160 Tbilisi (Georgia); Kahniashvili, Tina [Center for Cosmology and Particle Physics, New York University, 4 Washington Plaza, New York, New York 10003 (United States); National Abastumani Astrophysical Observatory, 2A Kazbegi Ave, GE-0160 Tbilisi (Georgia); Kosowsky, Arthur [Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, Pennsylvania 15260 (United States)
Lagrangian formulation of turbulent premixed combustion
The Lagrangian point of view is adopted to study turbulent premixed combustion. The evolution of the volume fraction of combustion products is established by the Reynolds transport theorem. It emerges that the burned-mass fraction is led by the turbulent particle motion, by the flame front velocity, and by the mean curvature of the flame front. A physical requirement connecting particle turbulent dispersion and flame front velocity is obtained from equating the expansion rates of the flame front progression and of the unburned particles spread. The resulting description compares favorably with experimental data. In the case of a zero-curvature flame, with a non-Markovian parabolic model for turbulent dispersion, the formulation yields the Zimont equation extended to all elapsed times and fully determined by turbulence characteristics. The exact solution of the extended Zimont equation is calculated and analyzed to bring out different regimes.
Pagnini, Gianni
On the theory of turbulent flame velocity
The renormalization ideas of self-similar dynamics of a strongly turbulent flame front are applied to the case of a flame with realistically large thermal expansion of the burning matter. In that case a flame front is corrugated both by external turbulence and the intrinsic flame instability. The analytical formulas for the velocity of flame propagation are obtained. It is demonstrated that the flame instability is of principal importance when the integral turbulent length scale is much larger than the cut off wavelength of the instability. The developed theory is used to analyse recent experiments on turbulent flames propagating in tubes. It is demonstrated that most of the flame velocity increase measured experimentally is provided by the large scale effects like the flame instability, and not by the small-scale external turbulence.
Vitaly Bychkov; Vyacheslav Akkerman; Arkady Petchenko
A dichotomy in the orientation of dust and radio jets in nearby low-power radio galaxies
We examine the properties of central dust in nearby quiescent and active early-type galaxies. The active galaxies are low-power radio galaxies with Fanaroff & Riley Type I or I/II radio jets. We focus on the comparison of the dust distributions in the active and quiescent galaxy samples and the relation between the radio jet and dust orientations. Our main observational conclusions are: (a) radio galaxies contain a higher fraction of regular dust 'ellipses' compared to quiescent galaxies which contain more often irregular dust distributions; (b) the morphology, size and orientation of dust ellipses and lanes in quiescent early-types and active early-types with kpc-scale radio jets is very similar; (c) dust ellipses are aligned with the major axis of the galaxy, dust lanes do not show a preferred alignment except for large (>kpc) dust lanes which are aligned with the minor axis of the galaxy. Dust morphologies can be classified as regular 'ellipses' and filamentary 'lanes'. We show that the dust ellipses are consistent with being nearly circular thin disks viewed at random viewing angles. The lanes are likely warped dust structures, which may be in the process of settling down to become regular disks or are being perturbed by a non-gravitational force. We use the observed dust-jet orientations to constrain the three-dimensional angle $\\theta_{\\rm DJ}$ between jet and dust. For dust-lane galaxies, the jet is approximately perpendicular to the dust structure, while for dust-ellipse galaxies there is a much wider distribution of $\\theta_{\\rm DJ}$. We discuss two scenarios that could explain the dust/jet/galaxy orientation dichotomy. (abridged)
Gijs Verdoes Kleijn; Tim de Zeeuw
Science Conference Proceedings (OSTI)
The Waste Treatment Plant (WTP) under construction at the Hanford Site will use pulse jet mixer (PJM) technology for mixing and gas retention control applications in tanks expected to contain waste slurries exhibiting a non-Newtonian rheology. This paper presents the results of theoretical and experimental studies undertaken to establish a methodology to perform reduced-scale mixing tests with PJM systems in non-Newtonian fluids. A theoretical model for mixing cavern formation from steady and pulsed jets is developed and compared with data from a single unsteady jet in a yield stress simulant. Dimensional analysis is used to identify the important dimensionless parameters affecting mixing performance in more complex systems. Scaling laws are proposed based on the modeling and dimensional analysis. Experimental validation of the scaling laws governing unsteady jet mixing in non-Newtonian fluids are also presented. Tests were conducted at three scales using two non-Newtonian simulants. The data were compared non-dimensionally, and the important scale laws were confirmed. The key dimensionless parameters were found to be the Strouhal number (which describes unsteady pulse jet mixer operation), the yield Reynolds number (which governs cavern formation due to non-Newtonian fluid behavior), and the viscous Reynolds number (which determines the flow regime and the degree of turbulence). The experimentally validated scaling laws provide the basis for reduced scale testing of prototypic WTP mixing systems. It is argued that mixing systems developed from reduced scale testing will produce conservative designs at full scale.
Meyer, Perry A.; Kurath, Dean E.; Bamberger, Judith A.; Barnes, Steven M.; Etchells, Arthur W.
The origin of GRBs have been a mystery for almost 30 years. The afterglowobserved in the last few years enabled redshift determination for a handful ofbursts, and the cosmological origin is now firmly established. Though thedistance scale is settled, there still remains orders of magnitude uncertaintyin their rate and in the total energy that is released in the explosion due tothe possibility that the emission is not spherical but jet-like. Contrary tothe GRB itself, the afterglow can be measured up to months and even years afterthe burst, and it can provide crucial information on the geometry of theejecta. We review the theory of afterglow from jets and discuss the evidencethat at least some of the bursts are not spherical. We discuss the prospects ofpolarization measurements, and show that this is a powerful tool inconstraining the geometry of the explosion.
Sari, R
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Terascale direct numerical simulations of turbulent combustion using S3D.
Computational science is paramount to the understanding of underlying processes in internal combustion engines of the future that will utilize non-petroleum-based alternative fuels, including carbon-neutral biofuels, and burn in new combustion regimes that will attain high efficiency while minimizing emissions of particulates and nitrogen oxides. Next-generation engines will likely operate at higher pressures, with greater amounts of dilution and utilize alternative fuels that exhibit a wide range of chemical and physical properties. Therefore, there is a significant role for high-fidelity simulations, direct numerical simulations (DNS), specifically designed to capture key turbulence-chemistry interactions in these relatively uncharted combustion regimes, and in particular, that can discriminate the effects of differences in fuel properties. In DNS, all of the relevant turbulence and flame scales are resolved numerically using high-order accurate numerical algorithms. As a consequence terascale DNS are computationally intensive, require massive amounts of computing power and generate tens of terabytes of data. Recent results from terascale DNS of turbulent flames are presented here, illustrating its role in elucidating flame stabilization mechanisms in a lifted turbulent hydrogen/air jet flame in a hot air co-flow, and the flame structure of a fuel-lean turbulent premixed jet flame. Computing at this scale requires close collaborations between computer and combustion scientists to provide optimized scaleable algorithms and software for terascale simulations, efficient collective parallel I/O, tools for volume visualization of multiscale, multivariate data and automating the combustion workflow. The enabling computer science, applied to combustion science, is also required in many other terascale physics and engineering simulations. In particular, performance monitoring is used to identify the performance of key kernels in the DNS code, S3D and especially memory intensive loops in the code. Through the careful application of loop transformations, data reuse in cache is exploited thereby reducing memory bandwidth needs, and hence, improving S3D's nodal performance. To enhance collective parallel I/O in S3D, an MPI-I/O caching design is used to construct a two-stage write-behind method for improving the performance of write-only operations. The simulations generate tens of terabytes of data requiring analysis. Interactive exploration of the simulation data is enabled by multivariate time-varying volume visualization. The visualization highlights spatial and temporal correlations between multiple reactive scalar fields using an intuitive user interface based on parallel coordinates and time histogram. Finally, an automated combustion workflow is designed using Kepler to manage large-scale data movement, data morphing, and archival and to provide a graphical display of run-time diagnostics.
Sankaran, Ramanan; Mellor-Crummy, J.; DeVries, M.; Yoo, Chun Sang; Ma, K. L.; Podhorski, N.; Liao, W. K.; Klasky, S.; de Supinski, B.; Choudhary, A.; Hawkes, Evatt R.; Chen, Jacqueline H.; Shende, Sameer
Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind
Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind C. S. Ng Center for Magnetic (MHD) turbulence Observations in ISM and solar wind · Anisotropy due to magnetic field · Electron MHD turbulence #12;Interstellar turbulence From Cordes (1999) Observation: power law relation between electron
Ng, Chung-Sang
Great Plains Turbulence Environment: Its Origins, Impact, and Simulation
This paper summarizes the known impacts of nocturnal turbulence on wind turbine performance and operations.
Kelley, N. D.; Jonkman, B. J.; Scott, G. N.
Modeling the motion of a hot, turbulent gas
Science Conference Proceedings (OSTI)
Keywords: animation, convection, gas simulations, gaseous phenomena, physics-based modeling, smoke, steam, turbulent flow
Nick Foster; Dimitris Metaxas
Relationships among nitric oxide, temperature and mixture fraction in hydrogen jet flames
Simultaneous point measurements of NO, the major species, mixture fraction, temperature, and OH are obtained in nonpremixed turbulent hydrogen jet flames, using the combination of spontaneous Raman scattering, Rayleigh scattering, and laser-induced fluorescence. Results are presented for an undiluted hydrogen flame at Reynolds number 10,000 and for flames with 20% and 40% helium dilution. Radial dependence of conditional mean NO mole fraction (conditional on mixture fraction) is shown to be small at upstream locations and negligible at the downstream locations that contribute most to the overall NO emission. Near the flame base, where NO formation rates and concentrations are sensitive to local strain, fluctuations of the NO mole fraction conditional on mixture fraction are 40 to 50% of conditional mean. When average NO levels are calculated conditional on both mixture fraction and temperature, a significant temperature dependence is found. However, this double conditioning does not substantially reduce NO fluctuations relative to the mean values. These results combined with previously reported data on the present hydrogen flames provide a detailed basis for evaluation and refinement of turbulent combustion models for thermal NO{sub x} formation in jet flames.
Barlow, R.S. [Sandia National Labs., Livermore, CA (United States); Carter, C.D. [Systems Research Labs., Inc., Dayton, OH (United States)
The effects of obstacle geometry on jet mixing in releases of silane
Releases of silane into air and the effects of obstacles were modeled with the Computational Fluid Dynamics (CFD) code, FLUENT. First the CFD code simulated the release of a free turbulent jet of silane into air to assure that the code agreed with established trends for turbulent jets. Then FLUENT was used to model the flow of silane when confined by a wall, or impinged by an obstacle such as a flat plate or a cylinder. Computer simulated concentration profiles of a silane and air mixture were analyzed to determine mixture volumes between the mixture explosive limits. For each volume of an explosive mixture, the volume of silane was determined. The volume of the flammable mixture and the amount of silane within the flammable mixture were normalized and determined as functions of obstacle radius and obstacle distance. lf the obstacle confines the entire volume, the volumes decrease as obstacle distance increases when the radial contribution dominates the volume. As the distance of the obstacle increases then the axial contribution dominates the volume so the volume increases. The volumes increase, decrease, or remain constant depending on the obstacle diameter.
Sposato, Christina F
Wind turbulence characterization for wind energy development
As part of its support of the US Department of Energy's (DOE's) Federal Wind Energy Program, the Pacific Northwest Laboratory (PNL) has initiated an effort to work jointly with the wind energy community to characterize wind turbulence in a variety of complex terrains at existing or potential sites of wind turbine installation. Five turbulence characterization systems were assembled and installed at four sites in the Tehachapi Pass in California, and one in the Green Mountains near Manchester, Vermont. Data processing and analyses techniques were developed to allow observational analyses of the turbulent structure; this analysis complements the more traditional statistical and spectral analyses. Preliminary results of the observational analyses, in the rotating framework or a wind turbine blade, show that the turbulence at a site can have two major components: (1) engulfing eddies larger than the rotor, and (2) fluctuating shear due to eddies smaller than the rotor disk. Comparison of the time series depicting these quantities at two sites showed that the turbulence intensity (the commonly used descriptor of turbulence) did not adequately characterize the turbulence at these sites. 9 refs., 10 figs.,
Wendell, L.L.; Gower, G.L.; Morris, V.R.; Tomich, S.D.
The online event selection is crucial to reject most of the events containing uninteresting background collisions while preserving as much as possible the interesting physical signals. The b-jet selection is part of the trigger strategy of the ATLAS experiment and a set of dedicated triggers was contributing to the event selection for the 2011 running. The b-jets acceptance is increased and the background reduced by lowering jet transverse energy thresholds at the first trigger level and applying b-tagging techniques at the subsequent levels. Different physics channels, especially topologies containing more than one b-jet where higher rejection factors are achieved, benefit from using the b-jet trigger. An overview of the b-jet trigger menu and performance on data is presented.
Per Hansson
Circular Economy Assessment for Coal-fired Power Plants Based on Supper-Efficiency DEA Model
Science Conference Proceedings (OSTI)
Coal-fired power plants are the main pollution source in most areas of China. The implementation of circular economy in coal-fired power plants is necessary for environmental protection and also an effective way of energy saving and emission reduction. ... Keywords: circular economy assessment, circular economy improvement, coal-fired power plant, super-efficiency data envelopment analysis
Shao-lun Zeng; Hong Hu; Wei Wang
Safe Fluids for Jet Engine Texts
Science Conference Proceedings (OSTI)
... industry and DoD use NIST calibration services for hydrocarbon liquid flow to ensure agreement and quality of measurements of jet fuel flow and ...
A range description for the planar circular Radon transform
The transform considered in the paper integrates a function supported in the unit disk on the plane over all circles centered at the boundary of this disk. Such circular Radon transform arises in several contemporary imaging techniques, as well as in other applications. As it is common for transforms of Radon type, its range has infinite co-dimension in standard function spaces. Range descriptions for such transforms are known to be very important for computed tomography, for instance when dealing with incomplete data, error correction, and other issues. A complete range description for the circular Radon transform is obtained. Range conditions include the recently found set of moment type conditions, which happens to be incomplete, as well as the rest of conditions that have less standard form. In order to explain the procedure better, a similar (non-standard) treatment of the range conditions is described first for the usual Radon transform on the plane.
Gaik Ambartsoumian; Peter Kuchment
Geometric transport along circular orbits in stationary axisymmetric spacetimes
Parallel transport along circular orbits in orthogonally transitive stationary axisymmetric spacetimes is described explicitly relative to Lie transport in terms of the electric and magnetic parts of the induced connection. The influence of both the gravitoelectromagnetic fields associated with the zero angular momentum observers and of the Frenet-Serret parameters of these orbits as a function of their angular velocity is seen on the behavior of parallel transport through its representation as a parameter-dependent Lorentz transformation between these two inner-product preserving transports which is generated by the induced connection. This extends the analysis of parallel transport in the equatorial plane of the Kerr spacetime to the entire spacetime outside the black hole horizon, and helps give an intuitive picture of how competing "central attraction forces" and centripetal accelerations contribute with gravitomagnetic effects to explain the behavior of the 4-acceleration of circular orbits in that spacetime.
Donato Bini; Christian Cherubini; Gianluca Cruciani; Robert T. Jantzen
Federal Acquisition Circular 2005-52 Item Subject FAR case
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
Circular 2005-52 Circular 2005-52 Item Subject FAR case I Sustainable Acquisition 2010-001 II Contract Closeout 2008-020 III Prohibition on Contracting with Inverted Domestic Corporations 2008-009 IV Buy American Exemption for Commercial Information Technology - Construction Material 2009-039 V Oversight of Contractor Ethics Programs 2010-017 VI Technical Amendments N/A Item I--Sustainable Acquisition (FAR Case 2010-001) (Interim) This interim rule amends the FAR to implement Executive Order 13514, Federal Leadership in Environmental, Energy, and Economic Performance, and Executive Order 13423, Strengthening Federal Environmental, Energy, and Transportation Management. It requires Federal agencies to leverage agency acquisitions to foster markets for
Mechanisms of Jet Formation on the Giant Planets
Science Conference Proceedings (OSTI)
The giant planet atmospheres exhibit alternating prograde (eastward) and retrograde (westward) jets of different speeds and widths, with an equatorial jet that is prograde on Jupiter and Saturn and retrograde on Uranus and Neptune. The jets are ...
Junjun Liu; Tapio Schneider
SpartyJet is a set of software tools for jet finding and analysis, built around the FastJet library of jet algorithms. SpartyJet provides four key extensions to FastJet: a simple Python interface to most FastJet features, a powerful framework for building up modular analyses, extensive input file handling capabilities, and a graphical browser for viewing analysis output and creating new on-the-fly analyses. Many of these capabilities rely on a ROOT-based backend. Beyond finding jets, many jet tools in SpartyJet perform measurement of jet or event variables, available to subsequent tools and stored in the final output. SpartyJet can be downloaded from HepForge at http://projects.hepforge.org/spartyjet.
Pierre-Antoine Delsart; Kurtis L. Geerlings; Joey Huston; Brian T. Martin; Christopher K. Vermilion
Circular hydraulic jump in generalized-Newtonian fluids
We carry out an analytical study of laminar circular hydraulic jumps, in generalized-Newtonian fluids obeying the two-parametric power-law model of Ostwald-de Waele. Under the boundary-layer approximation we obtained exact expressions determining the flow, an implicit relation for the jump radius is derived. Corresponding results for Newtonian fluids can be retrieved as a limiting case for the flow behavior index n=1, predictions are made for fluids deviating from Newtonian behavior.
Rai, Ashutosh; Poria, Swarup
Federal Acquisition Regulation; Federal Acquisition Circular 2005-47; Summary
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
7; Summary 7; Summary This document summarizes the Federal Acquisition Regulation (FAR) rules agreed to by the Civilian Agency Acquisition Council and the Defense Acquisition Regulations Council (Councils) in this Federal Acquisition Circular (FAC) 2005-47. All were effective December 13, 2010 except Items II, HUB Zone, and VI, Pass Through, which will be effective January 12, 2011. List of Rules in FAC 2005-47 Item Subject FAR case Analyst ------------------------------------------------------------------------------------------------------------ ---- I..................................... Notification of Employee 2010-006 McFadden.
File:DEQ MFSA Circular 1.pdf | Open Energy Information
DEQ MFSA Circular 1.pdf DEQ MFSA Circular 1.pdf Jump to: navigation, search File File history File usage File:DEQ MFSA Circular 1.pdf Size of this preview: 463 × 599 pixels. Other resolution: 464 × 600 pixels. Go to page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Go! next page → next page → Full resolution (1,275 × 1,650 pixels, file size: 313 KB, MIME type: application/pdf, 33 pages) File history Click on a date/time to view the file as it appeared at that time. Date/Time Thumbnail Dimensions User Comment current 16:00, 9 October 2012 Thumbnail for version as of 16:00, 9 October 2012 1,275 × 1,650, 33 pages (313 KB) Dklein2012 (Talk | contribs) You cannot overwrite this file. Edit this file using an external application (See the setup
Circular, elliptic and oval billiards in a gravitational field
We consider classical dynamical properties of a particle in a constant gravitational force and making specular reflections with circular, elliptic or oval boundaries. The model and collision map are described and a detailed study of the energy regimes is made. The linear stability of fixed points is studied, yielding exact analytical expressions for parameter values at which a period-doubling bifurcation occurs. The dynamics is apparently ergodic at certain energies in all three models, in contrast to the regularity of the circular and elliptic billiard dynamics in the field-free case. This finding is confirmed using a sensitive test involving Lyapunov weighted dynamics. In the last part of the paper a time dependence is introduced in the billiard boundary, where it is shown that for the circular billiard the average velocity saturates for zero gravitational force but in the presence of gravitational it increases with a very slow growth rate, which may be explained using Arnold diffusion. For the oval billiard, where chaos is present in the static case, the particle has an unlimited velocity growth with an exponent of approximately 1/6.
D. R. da Costa; C. P. Dettmann; E. D. Leonel
Science Conference Proceedings (OSTI)
Assuming that density waves trigger star formation, and that young stars preserve the velocity components of the molecular gas where they are born, we analyze the effects that non-circular gas orbits have on color gradients across spiral arms. We try two approaches, one involving semianalytical solutions for spiral shocks, and another with magnetohydrodynamic (MHD) numerical simulation data. We find that, if non-circular motions are ignored, the comparison between observed color gradients and stellar population synthesis models would in principle yield pattern speed values that are systematically too high for regions inside corotation, with the difference between the real and the measured pattern speeds increasing with decreasing radius. On the other hand, image processing and pixel averaging result in systematically lower measured spiral pattern speed values, regardless of the kinematics of stellar orbits. The net effect is that roughly the correct pattern speeds are recovered, although the trend of higher measured OMEGA{sub p} at lower radii (as expected when non-circular motions exist but are neglected) should still be observed. We examine the MartInez-GarcIa et al. photometric data and confirm that this is indeed the case. The comparison of the size of the systematic pattern speed offset in the data with the predictions of the semianalytical and MHD models corroborates that spirals are more likely to end at outer Lindblad resonance, as these authors had already found.
Martinez-Garcia, Eric E. [Centro de Investigaciones de Astronomia, Apartado Postal 264, Merida 5101-A (Venezuela, Bolivarian Republic of); Gonzalez-Lopezlira, Rosa A.; Gomez, Gilberto C., E-mail: firstname.lastname@example.com, E-mail: email@example.com, E-mail: firstname.lastname@example.com [Centro de Radioastronomia y Astrofisica, UNAM, Campus Morelia, Michoacan, C.P. 58089 (Mexico)
Stellar explosions, instabilities, and turbulence
Science Conference Proceedings (OSTI)
It has become very clear that the evolution of structure during supernovae is centrally dependent on the pre-existing structure in the star. Modeling of the pre-existing structure has advanced significantly, leading to improved understanding and to a physically based assessment of the structure that will be present when a star explodes. It remains an open question whether low-mode asymmetries in the explosion process can produce the observed effects or whether the explosion mechanism somehow produces jets of material. In any event, the workhorse processes that produce structure in an exploding star are blast-wave driven instabilities. Laboratory experiments have explored these blast-wave-driven instabilities and specifically their dependence on initial conditions. Theoretical work has shown that the relative importance of Richtmyer-Meshkov and Rayleigh-Taylor instabilities varies with the initial conditions and does so in ways that can make sense of a range of astrophysical observations.
Drake, R. P.; Kuranz, C. C. [University of Michigan, 2455 Hayward St., Ann Arbor, Michigan 48109 (United States); Miles, A. R. [Lawrence Livermore National Laboratory, 7500 East Ave., Livermore, California 94550 (United States); Muthsam, H. J. [Faculty of Mathematics, University of Vienna, Nordbergstr. 15, A-1090 Vienna (Austria); Plewa, T. [School of Computational Science, Florida State University, DSL 443, Tallahassee, Florida 32306 (United States)
Supercomputers Capture Turbulence in the Solar Wind
NLE Websites -- All DOE Office Websites (Extended Search)
Supercomputers Supercomputers Capture Turbulence in the Solar Wind Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space weather December 16, 2013 Linda Vu, +1 510 495 2402, email@example.com eddies1.jpg This visualization zooms in on current sheets revealing the "cascade of turbulence" in the solar wind occurring down to electron scales. This is a phenomenon common in fluid dynamics-turbulent energy injected at large eddies is transported to successively smaller scales until it is dissipated as heat. (Image by Burlen Loring, Berkeley Lab) As inhabitants of Earth, our lives are dominated by weather. Not just in the form of rain and snow from atmospheric clouds, but also a sea of charged particles and magnetic fields generated by a star sitting 93
Generation of Turbulence by Atmospheric Gravity Waves
Science Conference Proceedings (OSTI)
The standard current criterion for the generation of turbulence by atmospheric gravity waves and for the associated limitation on wave growth is based upon the standard criterion for static instability of the unperturbed atmosphere, namely, that ...
Colin O. Hines
Tracer dispersion in the turbulent convective layer
Science Conference Proceedings (OSTI)
Experimental results for passive tracer dispersion in the turbulent surface layer under convective conditions are presented. In this case, the dispersion of tracer particles is determined by the interplay of two mechanisms: buoyancy and advection. ...
Alex Skvortsov; Milan Jamriska; Timothy C. DuBois
Turbulence and Diapycnal Mixing in Drake Passage
Science Conference Proceedings (OSTI)
Direct measurements of turbulence levels in the Drake Passage region of the Southern Ocean show a marked enhancement over the Phoenix Ridge. At this site, the Antarctic Circumpolar Current (ACC) is constricted in its flow between the southern tip ...
L. St. Laurent; A. C. Naveira Garabato; J. R. Ledwell; A. M. Thurnherr; J. M. Toole; A. J. Watson
Stratified Turbulence near a Critical Dissipation Rate
Science Conference Proceedings (OSTI)
Turbulence in the thermocline was investigated using data observed by the submarine Dolphin. Various length scales, the Reynolds and the Froude numbers of the Dolphin data were compared to those values of a laboratory experiment presented in ...
Hidekatsu Yamazaki
Interstellar MHD Turbulence and Star Formation
This chapter reviews the nature of turbulence in the Galactic interstellar medium (ISM) and its connections to the star formation (SF) process. The ISM is turbulent, magnetized, self-gravitating, and is subject to heating and cooling processes that control its thermodynamic behavior. The turbulence in the warm and hot ionized components of the ISM appears to be trans- or subsonic, and thus to behave nearly incompressibly. However, the neutral warm and cold components are highly compressible, as a consequence of both thermal instability in the atomic gas and of moderately-to-strongly supersonic motions in the roughly isothermal cold atomic and molecular components. Within this context, we discuss: i) the production and statistical distribution of turbulent density fluctuations in both isothermal and polytropic media; ii) the nature of the clumps produced by thermal instability, noting that, contrary to classical ideas, they in general accrete mass from their environment; iii) the density-magnetic field correla...
Vazquez-Semadeni, Enrique
A Comparison of Turbulence Measurements from Aircraft
Science Conference Proceedings (OSTI)
A performance analysis of the three turbulence-measuring aircraft which participated in the GATE is presented. These aircraft were a Lockheed C-130 operated by the Meteorological Research Flight Centre of the U.K. Meteorological Office, a Douglas ...
Margaret A. Lemone; William T. Pennell
Observations of Turbulence in Stratified Flow
Science Conference Proceedings (OSTI)
Various theoretical properties of the structure function are evaluated. Additional functions are constructed to describe the overall influence of stratification, the anisotropy and intermittency of the turbulence, and the asymmetry of the main ...
L. Mahrt; N. Gamage
Radar Detection of Turbulence in Precipitation Environments
Science Conference Proceedings (OSTI)
Imperfect particle tracer response is incorporated into the relations describing the turbulent air motion contribution to Doppler radar spectrum mean and variance. Tracer effects on radar estimates of the eddy dissipation rate (?) increase with ...
Alan R. Bohne
An Analysis of Wave-Turbulence Interaction
Science Conference Proceedings (OSTI)
We present the results of an analytical and numerical calculation of the interaction between an internal gravity wave and a wave-induced turbulence. The initial atmospheric state, assumed horizontally homogeneous, is statically and dynamically ...
D. Fua; G. Chimonas; F. Einaudi; O. Zeman
A LES-Langevin model for turbulence
We propose a new model of turbulence for use in large-eddy simulations (LES). The turbulent force, represented here by the turbulent Lamb vector, is divided in two contributions. The contribution including only subfilter fields is deterministically modeled through a classical eddy-viscosity. The other contribution including both filtered and subfilter scales is dynamically computed as solution of a generalized (stochastic) Langevin equation. This equation is derived using Rapid Distortion Theory (RDT) applied to the subfilter scales. The general friction operator therefore includes both advection and stretching by the resolved scale. The stochastic noise is derived as the sum of a contribution from the energy cascade and a contribution from the pressure. The LES model is thus made of an equation for the resolved scale, including the turbulent force, and a generalized Langevin equation integrated on a twice-finer grid. The model is validated by comparison to DNS and is tested against classical LES models for i...
Laval, J P; Dubrulle, Berengere; Laval, Jean-Philippe
k-? turbulence modeling for a wind turbine.
?? In this report we discuss the use of k-? RANS (Reynolds-averaged Navier-Stokes equations) turbulence model for wind turbine applications. This model has been implemented� (more)
Active control for turbulent premixed flame simulations
Poinsot, T. J. , Combust. Flame, 121:395�417 [8] Trouve, A.Rutland, C. J. , Combust. Flame, 102:447�461 (1995). [10]Control for Turbulent Premixed Flame Simulations J. B. Bell,
Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Lijewski, Michael J.
Science Conference Proceedings (OSTI)
In the full-orbit particle simulations of energetic particle transport in plasmas, the plasma turbulence is typically described as a homogeneous superposition of linear Fourier modes. The turbulence evolution is, however, typically a nonlinear process, and, particularly in the heliospheric context, the solar wind plasma is inhomogeneous due to the transient structures, as observed by remote and in situ measurements. In this work, we study the effects of the inhomogeneities on energetic particle transport by using spatially distributed, superposed turbulence envelopes. We find that the cross-field transport is significantly reduced, when compared to the results obtained with homogeneous turbulence. The reduction can reach an order of magnitude when the enveloping breaks the wave phase coherence along the mean magnetic field direction.
Laitinen, T.; Dalla, S.; Kelly, J. [Jeremiah Horrocks Institute, University of Central Lancashire, PR1 2HE Preston (United Kingdom)
An Improved Model for the Turbulent PBL
Science Conference Proceedings (OSTI)
Second-order turbulence models of the Mellor and Yamada type have been widely used to simulate the planetary boundary layer (PBL). It is, however, known that these models have several deficiencies. For example, assuming the production of the ...
Y. Cheng; V. M. Canuto; A. M. Howard
Can Quasigeostrophic Turbulence Be Modeled Stochastically?
Science Conference Proceedings (OSTI)
Numerically generated data of quasigeostrophic turbulence in an equilibrated shear flow are analyzed to determine the extent to which they can be modeled by a Markov model. The time lagged covariances are collected into a matrix, C?, and are ...
Timothy DelSole
Marine Stratocumulus Layers. Part II: Turbulence Budgets
Science Conference Proceedings (OSTI)
This paper discusses the turbulence profiles and budgets for two days of radiation, dynamical and thermodynamical observations by the NCAR Electra in shallow marine stratocumulus off the California coast in June 1976.
R. A. Brost; J. C. Wyngaard; D. H. Lenschow
Example of Reduced Turbulence during Thunderstorm Outflow
Science Conference Proceedings (OSTI)
The vertical structures of turbulence, winds, and temperatures are analyzed from a 92-m instrumented tower and a collocated acoustic sodar during an outflow episode from a weak thunderstorm over sloping terrain in northern New Mexico. Prior to ...
Brent M. Bowen
Ertel's Potential Vorticity in Unstratified Turbulence
Science Conference Proceedings (OSTI)
The evolution of Ertel's potential vorticity (PV) is examined in direct numerical simulations (DNS) of decaying turbulence advecting passive scalars and in a generalized Taylor-Green vortex (TGV). It is noted that although PV itself is advected ...
J. R. Herring; R. M. Kerr; R. Rotunno
Estimating Oceanic Turbulence Dissipation from Seismic Images
Science Conference Proceedings (OSTI)
Seismic images of oceanic thermohaline finestructure record vertical displacements from internal waves and turbulence over large sections at unprecedented horizontal resolution. Where reflections follow isopycnals, their displacements can be used ...
W. Steven Holbrook; Ilker Fer; Raymond W. Schmitt; Daniel Lizarralde; Jody M. Klymak; L. Cody Helfrich; Robert Kubichek
Dispersion of Heavy Particles by Turbulent Motion
Science Conference Proceedings (OSTI)
Accurate prediction of heavy particle dispersion in turbulent flows requires a simultaneous consideration of particle's inertia and particle's drift velocity. A mathematically simple and physically comprehensive analysis was developed to solve ...
Lian-Ping Wang; Davd E. Stock
Angular Energy Distribution of Collapsar-Jets
Collapsars are fast-spinning, massive stars, whose core collapse liberates an energy, that can be channeled in the form of ultrarelativistic jets. These jets transport the energy from the collapsed core to large distances, where it is dissipated in the form of long-duration gamma-ray bursts. In this paper we study the dynamics of ultrarelativistic jets produced in collapsars. Also we extrapolate our results to infer the angular energy distribution of the produced outflows in the afterglow phase. Our main focus is to look for global energetical properties which can be imprinted by the different structure of different progenitor stars. Thus, we employ a number of pre-supernova, stellar models (with distinct masses and metallicities), and inject in all of them jets with fixed initial conditions. We assume that at the injection nozzle, the jet is mildly relativistic (Lorentz factor $\\sim 5$), has a finite half-opening angle ($5^\\circ$), and carries a power of $10^{51} $erg s$^{-1}$. These jets arrive intact to the stellar surface and break out of it. A large Lorentz factor region $\\Gamma\\simmore 100$ develops well before the jet reaches the surface of the star, in the unshocked part of the beam, located between the injection nozzle and the first recollimation shock. These high values of $\\Gamma$ are possible because the finite opening angle of the jet allows for free expansion towards the radial direction. We find a strong correlation between the angular energy distribution of the jet, after its eruption from the progenitor surface, and the mass of the progenitors. The angular energy distribution of the jets from light progenitor models is steeper than that of the jets injected in more massive progenitor stars. This trend is also imprinted in the angular distribution of isotropic equivalent energy.
Akira Mizuta; Miguel A. Aloy
Relativistic high harmonic generation in gas jet targets
We experimentally demonstrate a new regime of high-order harmonic generation by relativistic-irradiance lasers in gas jet targets. Bright harmonics with both odd and even orders, generated by linearly as well as circularly polarized pulses, are emitted in the forward direction, while the base harmonic frequency is downshifted. A 9 TW laser generates harmonics up to 360 eV, within the 'water window' spectral region. With a 120 TW laser producing 40 uJ/sr per harmonic at 120 eV, we demonstrate the photon number scalability. The observed harmonics cannot be explained by previously suggested scenarios. A novel high-order harmonics generation mechanism [T. Zh. Esirkepov et al., AIP Proceedings, this volume], which explains our experimental findings, is based on the phenomena inherent in the relativistic laser - underdense plasma interactions (self-focusing, cavity evacuation, and bow wave generation), mathematical catastrophe theory which explains formation of electron density singularities (cusps), and collective radiation due to nonlinear oscillations of a compact charge.
Pirozhkov, A.S.; Kando, M.; Esirkepov, T.Zh.; and others
Is there a statistical mechanics of turbulence
The statistical-mechanical treatment of turbulence is made questionable by strong nonlinearity and strong disequilibrium that result in the creation of ordered structures imbedded in disorder. Model systems are described which may provide some hope that a compact, yet faithful, statistical description of turbulence nevertheless is possible. Some essential dynamic features of the models are captured by low-order statistical approximations despite strongly non-Gaussian behavior. 31 refs., 5 figs.
Kraichnan, R.H.; Chen, S.Y.
Quantum light in the turbulent atmosphere
Nonclassical properties of light propagating through the turbulent atmosphere are studied. We demonstrate by numerical simulation that the probability distribution of the transmission coefficient, which characterizes the effects of the atmosphere on the quantum state of light, can be reconstructed by homodyne detection. Nonclassical photon-statistics and, more generally, nonclassical Glauber-Sudarshan functions appear to be more robust against turbulence for weak light fields rather than for bright ones.
A. A. Semenov; W. Vogel
HEFA and F-T jet fuel cost analyses
Aviation and the Environment 2. HEFA jet fuel from vegetable oil bottom-up cost study 3. HEFA jet fuel from microalgae bottom-up cost
Nick Carter; Michael Bredehoeft; Christoph Wollersheim; Hakan Olcay; James Hileman; Steven Barrett; Website Lae. Mit. Edu
Jet Fuel Supply/Price Outlook - Fueling the Recovery
U.S. Energy Information Administration (EIA)
Jet Fuel Supply/Price Outlook: Fueling the Recovery Energy Information Administration Presentation to 4th International Jet Fuel Conference February ...
Enhanced boiling heat transfer by submerged, vibration induced jets .
??In this analysis, the efficacy of cavitation jets for heat transfer enhancement was demonstrated. The cavitation jet was formed from a cluster of cavitation bubbles� (more)
Tillery, Steven W.
Aerosol Jet� Material Deposition for High Resolution Printed ...
Science Conference Proceedings (OSTI)
Abstract Scope, Aerosol Jet printing, is finding wide use in a number of ... The Aerosol Jet systems deposit a wide variety of functional materials onto a wide�...
Autoignition in turbulent two-phase flows
in the following section. 1.2 Diesel engine combustion Compression-ignition (CI) engines are the most fuel-efficient engines ever devel- oped for transportation purposes [28]. This is due to their higher compression ratio and absence of throttling losses... within the bulk gas, leading to air entrainment. As the cold liquid jet is heated by mixing with the hot oxidizer, a thin sheet of air / fuel vapor mixture is formed around the jet�s periphery. Further entrainment of hot air is responsible for start- ing...
Borghesi, Giulio
Diffusion Processes in Turbulent Magnetic Fields
We study of the effect of turbulence on diffusion processes within magnetized medium. While we exemplify our treatment with heat transfer processes, our results are quite general and are applicable to different processes, e.g. diffusion of heavy elements. Our treatment is also applicable to describing the diffusion of cosmic rays arising from magnetic field wandering. In particular, we find that when the energy injection velocity is smaller than the Alfven speed the heat transfer is partially suppressed, while in the opposite regime the effects of turbulence depend on the intensity of driving. In fact, the scale $l_A$ at which the turbulent velocity is equal the Alfven velocity is a new important parameter. When the electron mean free path $\\lambda$ is larger than $l_A$, the stronger the the turbulence, the lower thermal conductivity by electrons is. The turbulent motions, however, induces their own advective transport, that can provide effective diffusivity. For clusters of galaxies, we find that the turbulence is the most important agent for heat transfer. We also show that the domain of applicability of the subdiffusion concept is rather limited.
Alex Lazarian
Diffusion Processes in Turbulent Magnetic Fields
We study of the effect of turbulence on diffusion processes within magnetized medium. While we exemplify our treatment with heat transfer processes, our results are quite general and are applicable to different processes, e.g. diffusion of heavy elements. Our treatment is also applicable to describing the diffusion of cosmic rays arising from magnetic field wandering. In particular, we find that when the energy injection velocity is smaller than the Alfven speed the heat transfer is partially suppressed, while in the opposite regime the effects of turbulence depend on the intensity of driving. In fact, the scale $l_A$ at which the turbulent velocity is equal the Alfven velocity is a new important parameter. When the electron mean free path $\\lambda$ is larger than $l_A$, the stronger the the turbulence, the lower thermal conductivity by electrons is. The turbulent motions, however, induces their own advective transport, that can provide effective diffusivity. For clusters of galaxies, we find that the turbule...
Lazarian, Alex
Effects of Coaxial Air on Nitrogen-Diluted Hydrogen Jet Diffusion Flame Length and NOx Emission
Turbulent nitrogen-diluted hydrogen jet diffusion flames with high velocity coaxial air flows are investigated for their NOx emission levels. This study is motivated by the DOE turbine program�s goal of achieving 2 ppm dry low NOx from turbine combustors running on nitrogen-diluted high-hydrogen fuels. In this study, effects of coaxial air velocity and momentum are varied while maintaining low overall equivalence ratios to eliminate the effects of recirculation of combustion products on flame lengths, flame temperatures, and resulting NOx emission levels. The nature of flame length and NOx emission scaling relationships are found to vary, depending on whether the combined fuel and coaxial air jet is fuel-rich or fuel-lean. In the absence of differential diffusion effects, flame lengths agree well with predicted trends, and NOx emissions levels are shown to decrease with increasing coaxial air velocity, as expected. Normalizing the NOx emission index with a flame residence time reveals some interesting trends, and indicates that a global flame strain based on the difference between the fuel and coaxial air velocities, as is traditionally used, is not a viable parameter for scaling the normalized NOx emissions of coaxial air jet diffusion flames.
Weiland, N.T.; Chen, R.-H.; Strakey, P.A.
Inertial Resonance Induced by an Oceanic Jet
Science Conference Proceedings (OSTI)
The dynamics of the mixed layer in the presence of an embedded geostrophic jet has been investigated using a simple 1�-layer model and a two-dimensional primitive equation model. The jet vorticity induces a spatial variability of the wind-driven ...
P. Klein; A. M. Treguier
Electro jet drilling using hybrid NNGA approach
Science Conference Proceedings (OSTI)
This paper presents a hybrid neural network and genetic algorithm (NNGA) approach for the multi-response optimization of the electro jet drilling (EJD) process. The approach first uses a neural network model to predict the response parameters of the ... Keywords: Electro jet drilling, Electrochemical machining, Genetic algorithm, Multi-response, Neural network, Optimization
Mohan Sen; H. S. Shan
Dynamics of the West African Westerly Jet
Science Conference Proceedings (OSTI)
The West African westerly jet (WAWJ) is a low-level westerly jet located at 8��11�N over the eastern Atlantic and the West African coast. It is clearly distinguished from the monsoon westerly flow by its structure and dynamics, and plays an ...
Bing Pu; Kerry H. Cook
??The Radial Jet Reattachment (RJR) nozzle was developed over the past decade as a modification of the In-Line Jet (ILJ) nozzle in order to enhance� (more)
Narayanan, Vinod
Hypervelocity jets from conical hollow-charges
Science Conference Proceedings (OSTI)
In this article the formation of jets by means of the implosion of conical targets is analyzed. This implosion might be induced by high intensity lasers or X rays. It is known of experiments with explosive and numeric simulations that the formation of jets depends critically on the aperture of the cone. It is found in these simulations that for a given collapsing speed an angle of the cone exists below which jet doesn't take place. This critical angle grows with the collapsing speed. The numerical simulations seem to indicate that the production of jets is related to the separation of the shock wave that takes place in the collapsing region. We will also analyze the mass and kinetic energy of the jets taken place as a function of the initial opening of the cone.
Velarde, P. M.; Martinez-Val, J. M.; Eliezer, S.; Piera, M.; Guillen, J.; Cobo, M. D.; Ogando, F.; Crisol, A.; Gonzalez, L.; Prieto, J.; Velarde, G. [Instituto de Fusion Nuclear Universidad Politecnico de Madrid Jose Gutierrez Abascal 2, 28006 Madrid (Spain)
Understanding and identifying ditau jets--jets consisting of pairs of tau particles--can be of crucial importance and may even turn out to be a necessity if the Higgs boson decays dominantly to new light scalars which, on the other hand, decay to tau pairs. As often seen in various models beyond the standard model such as in the next-to-minimal supersymmetric standard model, Higgs portals, etc., the lightness of these new states ensures their large transverse momenta and, as a consequence, the collinearity of their decay products. We show that the nonstandard signatures of these objects, which can easily be missed by standard analysis techniques, can be superbly exploited in an analysis based on subjet observables. When combined with additional selection strategies, this analysis can even facilitate an early discovery of the Higgs boson. To be specific, a light Higgs can be found with S/{radical}(B) > or approx. 5 from L{approx_equal}12 fb{sup -1} of data. We combine all these observables into a single discriminating likelihood that can be employed toward the construction of a realistic and standalone ditau tagger.
Englert, Christoph; Roy, Tuhin S.; Spannowsky, Michael [Institute for Theoretical Physics, Heidelberg University, 69120 Heidelberg (Germany); Department of Physics, University of Washington, Seattle, Washington 98195 (United States); Institute of Theoretical Science, University of Oregon, Eugene, Oregon 97403 (United States)
Evidence of critical balance in kinetic Alfven wave turbulence simulations
Science Conference Proceedings (OSTI)
A numerical simulation of kinetic plasma turbulence is performed to assess the applicability of critical balance to kinetic, dissipation scale turbulence. The analysis is performed in the frequency domain to obviate complications inherent in performing a local analysis of turbulence. A theoretical model of dissipation scale critical balance is constructed and compared to simulation results, and excellent agreement is found. This result constitutes the first evidence of critical balance in a kinetic turbulence simulation and provides evidence of an anisotropic turbulence cascade extending into the dissipation range. We also perform an Eulerian frequency analysis of the simulation data and compare it to the results of a previous study of magnetohydrodynamic turbulence simulations.
TenBarge, J. M.; Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)
On the Nature of Turbulence in a Stratified Fluid. Part I: The Energetics of Mixing
Science Conference Proceedings (OSTI)
The definition of the flux Richardson number Rf is generalized to be the ratio of the turbulent buoyancy flux b to the net turbulent mechanical energy m available from all sources. For mechanically energized turbulence where turbulence kinetic ...
G. N. Ivey; J. Imberger
Particle creation in (2+1) circular dust collapse
We investigate the quantum particle creation during the circularly symmetric collapse of a 2+1 dust cloud, for the cases when the cosmological constant is either zero or negative. We derive the Ford-Parker formula for the 2+1 case, which can be used to compute the radiated quantum flux in the geometric optics approximation. It is shown that no particles are created when the collapse ends in a naked singularity, unlike in the 3+1 case. When the collapse ends in a BTZ black hole, we recover the expected Hawking radiation. 1
Sashideep Gutti; T. P. Singh
Helix untwisting and bubble formation in circular DNA
The base pair fluctuations and helix untwisting are examined for a circular molecule. A realistic mesoscopic model including twisting degrees of freedom and bending of the molecular axis is proposed. The computational method, based on path integral techniques, simulates a distribution of topoisomers with various twist numbers and finds the energetically most favorable molecular conformation as a function of temperature. The method can predict helical repeat, openings loci and bubble sizes for specific sequences in a broad temperature range. Some results are presented for a short DNA circle recently identified in mammalian cells.
Zoli, Marco
Transmission characteristics of circular metallic waveguides for terahertz radiation
Transmission characteristics of oversized circular metallic waveguides excited by linearly polarised Gaussian laser beams in the terahertz range (4 - 28 THz) are studied theoretically and experimentally. Calculating the transmission characteristics, we have determined the conditions of applicability of the method of the eigenoscillations in the approximations of a real metal by an ideal metal or dielectric, depending on the transmitted radiation frequency. The existence of the transition region is established in the behaviour of the electrodynamic properties of metallic waveguides in the frequency range of 7.5 - 15 THz.
Volodenko, A V; Gurin, O V; Degtyarev, A V; Maslov, Vyacheslav A; Svich, V A; Senyuta, V S; Topkov, A N [V.N. Karazin Kharkov National University, Kharkov (Ukraine)
Composite Octet Searches with Jet Substructure
Science Conference Proceedings (OSTI)
Many new physics models with strongly interacting sectors predict a mass hierarchy between the lightest vector meson and the lightest pseudoscalar mesons. We examine the power of jet substructure tools to extend the 7 TeV LHC sensitivity to these new states for the case of QCD octet mesons, considering both two gluon and two b-jet decay modes for the pseudoscalar mesons. We develop both a simple dijet search using only the jet mass and a more sophisticated jet substructure analysis, both of which can discover the composite octets in a dijet-like signature. The reach depends on the mass hierarchy between the vector and pseudoscalar mesons. We find that for the pseudoscalar-to-vector meson mass ratio below approximately 0.2 the simple jet mass analysis provides the best discovery limit; for a ratio between 0.2 and the QCD-like value of 0.3, the sophisticated jet substructure analysis has the best discovery potential; for a ratio above approximately 0.3, the standard four-jet analysis is more suitable.
Bai, Yang; /SLAC; Shelton, Jessie; /Yale U.
Anisotropic turbulent model for solar coronal heating
Context : We present a self-consistent model of solar coronal heating, originally developed by Heyvaert & Priest (1992), in which we include the dynamical effect of the background magnetic field along a coronal structure by using exact results from wave MHD turbulence (Galtier et al. 2000). Aims : We evaluate the heating rate and the microturbulent velocity for comparison with observations in the quiet corona, active regions and also coronal holes. Methods :The coronal structures are assumed to be in a turbulent state maintained by the slow erratic motions of the magnetic footpoints. A description for the large-scale and the unresolved small-scale dynamics are given separately. From the latter, we compute exactly (or numerically for coronal holes) turbulent viscosites that are finally used in the former to close self-consistently the system and derive the heating flux expression. Results : We show that the heating rate and the turbulent velocity compare favorably with coronal observations. Conclusions : Although the Alfven wave turbulence regime is strongly anisotropic, and could reduce a priori the heating efficiency, it provides an unexpected satisfactory model of coronal heating for both magnetic loops and open magnetic field lines.
B. Bigot; S. Galtier; H. Politano
Clustering of Aerosols in Atmospheric Turbulent Flow
A mechanism of formation of small-scale inhomogeneities in spatial distributions of aerosols and droplets associated with clustering instability in the atmospheric turbulent flow is discussed. The particle clustering is a consequence of a spontaneous breakdown of their homogeneous space distribution due to the clustering instability, and is caused by a combined effect of the particle inertia and a finite correlation time of the turbulent velocity field. In this paper a theoretical approach proposed in Phys. Rev. E 66, 036302 (2002) is further developed and applied to investigate the mechanisms of formation of small-scale aerosol inhomogeneities in the atmospheric turbulent flow. The theory of the particle clustering instability is extended to the case when the particle Stokes time is larger than the Kolmogorov time scale, but is much smaller than the correlation time at the integral scale of turbulence. We determined the criterion of the clustering instability for the Stokes number larger than 1. We discussed applications of the analyzed effects to the dynamics of aerosols and droplets in the atmospheric turbulent flow.
T. Elperin; N. Kleeorin; M. A. Liberman; V. L'vov; I. Rogachevskii
A hydrogen jet polarimeter was developed for the RHIC accelerator to improve the process of measuring polarization. Particle beams intersecting with gas molecules can produce light by the process known as luminescence. This light can then be focused, collected, and processed giving important information such as size, position, emittance, motion, and other parameters. The RHIC hydrogen jet polarimeter was modified in 2005 with specialized optics, vacuum windows, light transport, and a new camera system making it possible to monitor the luminescence produced by polarized protons intersecting the hydrogen beam. This paper describes the configuration and preliminary measurements taken using the RHIC hydrogen jet polarimeter as a luminescence monitor.
Study of falling-jet flash evaporators
Experimental results of flash evaporation from sheets of water, 3.2 mm and 6.3 mm thick and 27.9 cm wide, falling freely in the presence of their own vapor, are reported. With no flashing the jets fall in coherent sheets, but with flashing the jets were observed to spread and break up into droplets. Flashing was characterized by an effectiveness parameter, which was found to increase with increasing water temperature and jet length. Variations in water flow rate and heat flux did not influence the effectiveness appreciably.
Kreith, F.; Olson, D.A.; Bharathan, D.; Green, H.J.
Jet spoiler arrangement for wind turbine
An air jet spoiler arrangement is provided for a Darrieus-type vertical axis wind-powered turbine. Air is drawn into hollow turbine blades through air inlets at the ends thereof and is ejected in the form of air jets through small holes or openings provided along the lengths of the blades. The air jets create flow separation at the surfaces of the turbine blades, thereby inducing stall conditions and reducing the output power. A feedback control unit senses the power output of the turbine and controls the amount of air drawn into the air inlets accordingly.
Cyrus, Jack D. (Corrales, NM); Kadlec, Emil G. (Albuquerque, NM); Klimas, Paul C. (Albuquerque, NM)
Jet spoiler arrangement for wind turbine
An air jet spoiler arrangement is provided for a Darrieus-type vertical axis wind-powered turbine. Air is drawn into hollow turbine blades through air inlets at the end thereof and is ejected in the form of air jets through small holes or openings provided along the lengths of the blades. The air jets create flow separation at the surfaces of the turbine blades, thereby including stall conditions and reducing the output power. A feedback control unit senses the power output of the turbine and controls the amount of air drawn into the air inlets accordingly.
Cyrus, J.D.; Kadlec, E.G.; Klimas, P.C.
Velcro Measurement of Turbulence Kinetic Energy Dissipation Rate ?
Science Conference Proceedings (OSTI)
Turbulence in the ocean results from many different processes operating over a wide range of space scales and timescales, with spatial and temporal variability particularly extreme in coastal oceans. If the origins and effects of turbulent ...
Ann E. Gargett
Observations of the Surf-Zone Turbulent Dissipation Rate
Science Conference Proceedings (OSTI)
The contributions of surface (breaking wave) boundary layer (SBL) and bottom (velocity shear) boundary layer (BBL) processes to surf-zone turbulence is studied here. The turbulent dissipation rate ?, estimated on a 160-m-long cross-shore ...
Falk Feddersen
Wave�Turbulence Interactions in a Breaking Mountain Wave
Science Conference Proceedings (OSTI)
The mean and turbulent structures in a breaking mountain wave are considered through an ensemble of high-resolution (essentially large-eddy simulation) wave-breaking calculations. Of particular interest are the turbulent heat and momentum fluxes ...
Craig C. Epifanio; Tingting Qian
Boils and Turbulence in a Weakly Stratified Shallow Tidal Sea
Science Conference Proceedings (OSTI)
Measurements of turbulence are made in a weakly but variably stratified region of tidal straining in the eastern Irish Sea using turbulence sensors profiling vertically through the water column on the Fast Light Yo-yo (FLY) profiler and ...
S. A. Thorpe; J. A. M. Green; J. H. Simpson; T. R. Osborn; W. A. M. Nimmo Smith
The New Cardington Balloon-Borne Turbulence Probe System
Science Conference Proceedings (OSTI)
A new instrument package has been developed to measure turbulence at various heights in the boundary layer. The package or �turbulence probe� is designed to be attached to the tethering cable of a balloon. In contrast to previous balloon borne ...
A. J. Lapworth; P. J. Mason
Modeling Turbulent Flow in an Urban Central Business District
Science Conference Proceedings (OSTI)
The Realistic Urban Spread and Transport of Intrusive Contaminants (RUSTIC) model has been developed as a simplified computational fluid dynamics model with a k�? turbulence model to be used to provide moderately fast simulations of turbulent ...
Donald A. Burrows; Eric A. Hendricks; Steve R. Diehl; Robert Keith
Turbulence Sensor Dynamic Calibration Using Real-Time Spectral Computations
Science Conference Proceedings (OSTI)
The integration of plug-in Fast Fourier Transform (FFT) boards in data acquisition computers allows a considerable development in the dynamic calibration of turbulence sensors. The spectral transfer function of a fast and sensitive turbulence ...
P. G. Mestayer; S. E. Larsen; C. W. Fairall; J. B. Edson
Dispersion of Marked Fluid Elements in a Turbulent Ekman Layer
Science Conference Proceedings (OSTI)
A stochastic model is derived for studying shear-dispersion in a horizontally homogeneous, turbulent Ekman layer that is evolving in time. It is based on a one-dimensional model including an advanced turbulence closure (k = ?) model, which yields ...
Lars-Arne Rahm; Urban Svensson
Modeling Optical Turbulence and Seeing over Mauna Kea
Science Conference Proceedings (OSTI)
Atmospheric turbulence is a primary concern for astronomers. Turbulence causes amplitude and phase fluctuations in electromagnetic waves propagating through the atmosphere, constraining the maximum telescope resolution and resulting in telescope ...
T. Cherubini; S. Businger; R. Lyman; M. Chun
Effective Roughness Length for Turbulent Flow over a Wavy Surface
Science Conference Proceedings (OSTI)
A two-equation turbulence model is used to calculate the effective roughness length for two-dimensional turbulent flow over small amplitude, wavy surface topography. The governing equations are solved using the method of matched asymptotic ...
S. J. Jacobs
Statistics and Dynamics of Aircraft Encounters of Turbulence over Greenland
Science Conference Proceedings (OSTI)
Historical records of aviation turbulence encounters above Greenland are examined for the period from 2000 to 2006. These data identify an important flow regime that contributes to the occurrence of aircraft turbulence encounters, associated with ...
Todd P. Lane; James D. Doyle; Robert D. Sharman; Melvyn A. Shapiro; Campbell D. Watson
Turbulence Closure, Steady State, and Collapse into Waves
Science Conference Proceedings (OSTI)
A new simple two-equation turbulence closure is constructed by hypothesizing that there is an extra energy sink in the turbulent kinetic energy (k) equation representing the transfer of energy from k to internal waves and other nonturbulent ...
Helmut Baumert; Hartmut Peters
Comments on �Turbulence Closure, Steady State, and Collapse into Waves�
Science Conference Proceedings (OSTI)
Two-equation models are being increasingly used to model turbulence in geophysical flows. A salient aspect of these flows is the stable gravitational stratification, which implies that turbulent fluctuations can generate internal waves that drain ...
Lakshmi H. Kantha
Turbulent burning rates of methane and methane-hydrogen mixtures
Science Conference Proceedings (OSTI)
Methane and methane-hydrogen (10%, 20% and 50% hydrogen by volume) mixtures have been ignited in a fan stirred bomb in turbulence and filmed using high speed cine schlieren imaging. Measurements were performed at 0.1 MPa (absolute) and 360 K. A turbulent burning velocity was determined for a range of turbulence velocities and equivalence ratios. Experimental laminar burning velocities and Markstein numbers were also derived. For all fuels the turbulent burning velocity increased with turbulence velocity. The addition of hydrogen generally resulted in increased turbulent and laminar burning velocity and decreased Markstein number. Those flames that were less sensitive to stretch (lower Markstein number) burned faster under turbulent conditions, especially as the turbulence levels were increased, compared to stretch-sensitive (high Markstein number) flames. (author)
Fairweather, M. [School of Process, Environmental and Materials Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Ormsby, M.P.; Sheppard, C.G.W. [School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Woolley, R. [Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)
Collision Rates of Cloud Droplets in Turbulent Flow
Science Conference Proceedings (OSTI)
Direct numerical simulations of an evolving turbulent flow field have been performed to explore how turbulence affects the motion and collisions of cloud droplets. Large numbers of droplets are tracked through the flow field and their positions, ...
Charmaine N. Franklin; Paul A. Vaillancourt; M. K. Yau; Peter Bartello
Turbulent Condensation of Droplets: Direct Simulation and a Stochastic Model
Science Conference Proceedings (OSTI)
The effect of turbulent mixing on droplet condensation is studied via direct numerical simulations of a population of droplets in a periodic box of homogeneous isotropic turbulence. Each droplet is tracked as a fluid particle whose radius grows ...
Roberto Paoli; Karim Shariff
Observations of Quasi-Two-Dimensional Turbulence in Tidal Currents
Science Conference Proceedings (OSTI)
Observational evidence for the existence of quasi-two-dimensional turbulence in tidal currents is derived from the auto- and cross-correlation spectra of vertically separated current meters. The observed quasi- two-dimensional turbulence seems to ...
C. Veth; J. T. F. Zimmerman
Observations of Turbulence within a Natural Surf Zone
Science Conference Proceedings (OSTI)
Here, the Reynolds stresses u?w? and ??w?, where u?, ??, and w? are the cross-shore, alongshore, and vertical turbulence velocities, respectively, and the angle brackets represent time averaging, are used to diagnose turbulence dynamics ...
B. G. Ruessink
An Investigation of Turbulence Generation Mechanisms above Deep Convection
Science Conference Proceedings (OSTI)
An investigation of the generation of turbulence above deep convection is presented. This investigation is motivated by an encounter between a commercial passenger aircraft and severe turbulence above a developing thunderstorm near Dickinson, ...
Todd P. Lane; Robert D. Sharman; Terry L. Clark; Hsiao-Ming Hsu
Statistical theory of Langmuir turbulence. [Direct interaction approximation
A statistical theory of Langmuir turbulence is developed by applying a generalization of the direction interaction approximation (DIA) of Kraichnan to the Zakharov equations describing Langmuir turbulence. 7 references.
DuBois, D.F.; Rose, H.A.; Goldman, M.V.
Recent Advances in the Understanding of Near-Cloud Turbulence
Science Conference Proceedings (OSTI)
Anyone who has flown in a commercial aircraft is familiar with turbulence. Unexpected encounters with turbulence pose a safety risk to airline passengers and crew, can occasionally damage aircraft, and indirectly increase the cost of air travel. Deep ...
Todd P. Lane; Robert D. Sharman; Stanley B. Trier; Robert G. Fovell; John K. Williams
Drag, turbulence, and diffusion in flow through emergent vegetation
Aquatic plants convert mean kinetic energy into turbulent kinetic energy at the scale of the plant stems and branches. This energy transfer, linked to wake generation, affects vegetative drag and turbulence intensity. ...
Nepf, Heidi
We carry out a general study of the stability of astrophysical flows that appear steady in a uniformly rotating frame. Such a flow might correspond to a stellar pulsation mode or an accretion disk with a free global distortion giving it finite eccentricity. We consider perturbations arbitrarily localized in the neighbourhood of unperturbed fluid streamlines.When conditions do not vary around them, perturbations take the form of oscillatory inertial or gravity modes. However, when conditions do vary so that a circulating fluid element is subject to periodic variations, parametric instability may occur. For nearly circular streamlines, the dense spectra associated with inertial or gravity modes ensure that resonance conditions can always be satisfied when twice the period of circulation round a streamline falls within. We apply our formalism to a differentially rotating disk for which the streamlines are Keplerian ellipses, with free eccentricity up to 0.7, which do not precess in an inertial frame. We show that for small $e,$ the instability involves parametric excitation of two modes with azimuthal mode number differing by unity in magnitude which have a period of twice the period of variation as viewed from a circulating unperturbed fluid element. Instability persists over a widening range of wave numbers with increasing growth rates for larger eccentricities. The nonlinear outcome is studied in a follow up paper which indicates development of small scale subsonic turbulence.
J. C. B. Papaloizou
Supercomputers Capture Turbulence in the Solar Wind
NLE Websites -- All DOE Office Websites (Extended Search)
Supercomputers Capture Supercomputers Capture Turbulence in the Solar Wind News & Publications ESnet in the News ESnet News Media & Press Publications and Presentations Galleries ESnet Awards and Honors Contact Us Technical Assistance: 1 800-33-ESnet (Inside the US) 1 800-333-7638 (Inside the US) 1 510-486-7600 (Globally) 1 510-486-7607 (Globally) Report Network Problems: email@example.com Provide Web Site Feedback: firstname.lastname@example.com Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space weather December 16, 2013 | Tags: ESnet News, National Energy Research Scientific Computing Linda Vu, +1 510 495 2402, firstname.lastname@example.com eddies1.jpg This visualization zooms in on current sheets revealing the "cascade of turbulence" in the solar wind occurring down to electron scales. This is
Boundary Plasma Turbulence Simulations for Tokamaks
The boundary plasma turbulence code BOUT models tokamak boundary-plasma turbulence in a realistic divertor geometry using modified Braginskii equations for plasma vorticity, density (ni), electron and ion temperature (T{sub e}; T{sub i}) and parallel momenta. The BOUT code solves for the plasma fluid equations in a three dimensional (3D) toroidal segment (or a toroidal wedge), including the region somewhat inside the separatrix and extending into the scrape-off layer; the private flux region is also included. In this paper, a description is given of the sophisticated physical models, innovative numerical algorithms, and modern software design used to simulate edge-plasmas in magnetic fusion energy devices. The BOUT code's unique capabilities and functionality are exemplified via simulations of the impact of plasma density on tokamak edge turbulence and blob dynamics.
Xu, X; Umansky, M; Dudson, B; Snyder, P
Turbulent Density Spectrum in Solar Wind Plasma
The density fluctuation spectrum in the solar wind reveals a Kolmogorov-like scaling with a spectral slope of -5/3 in wavenumber space. The energy transfer process in the magnetized solar wind, characterized typically by MHD turbulence, over extended length-scales remains an unresolved paradox of modern turbulence theories, raising the question of how a compressible magnetofluid exhibits a turbulent spectrum that is characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfv\\'enic, supersonic and strongly magnetized plasma fluid. It is shown that a Kolmogorov-like density spectrum can develop by plasma motions that are dominated by Alfv\\'enic cascades whereas compressive modes are dissipated.
Shaikh, Dastgeer
Turbulent Spectra in the Solar Wind Plasma
Observations of interstellar scintillations at radio wavelengths reveal a Kolmogorov-like scaling of the electron density spectrum with a spectral slope of -5/3 over six decades in wavenumber space. A similar turbulent density spectrum in the solar wind plasma has been reported. The energy transfer process in the magnetized solar wind plasma over such extended length-scales remains an unresolved paradox of modern turbulence theories raising the especially intriguing question of how a compressible magnetized solar wind exhibits a turbulent spectrum that is a characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfv\\'enic, supersonic and strongly magnetized plasma. It is shown that the observed Kolmogorov-like (-5/3) spectrum can develop in the solar wind plasma by supersonic plasma motions that dissipate into highly subsonic motion that passively ...
Shaikh, Dastgeer
Jet production in muon scattering at Fermilab E665
Measurements of multi-jet production rates from Muon-Nucleon and Muon-Nuclei scattering at Fermilab-E665 are presented. Jet rates are defined by the JADE clustering algorithm. Rates in Muon-Nucleon deep-inelastic scattering are compared to Monte Carlo model predictions. Preliminary results from jet production on heavy targets, in the shadowing region, show a higher suppression of two-forward jets as compared to one-forward jet production.
Salgado, C.W.; E665 Collaboration
Statistical theory of turbulent incompressible multimaterial flow
Science Conference Proceedings (OSTI)
Interpenetrating motion of incompressible materials is considered. ''Turbulence'' is defined as any deviation from the mean motion. Accordingly a nominally stationary fluid will exhibit turbulent fluctuations due to a single, slowly moving sphere. Mean conservation equations for interpenetrating materials in arbitrary proportions are derived using an ensemble averaging procedure, beginning with the exact equations of motion. The result is a set of conservation equations for the mean mass, momentum and fluctuational kinetic energy of each material. The equation system is at first unclosed due to integral terms involving unknown one-point and two-point probability distribution functions. In the mean momentum equation, the unclosed terms are clearly identified as representing two physical processes. One is transport of momentum by multimaterial Reynolds stresses, and the other is momentum exchange due to pressure fluctuations and viscous stress at material interfaces. Closure is approached by combining careful examination of multipoint statistical correlations with the traditional physical technique of kappa-epsilon modeling for single-material turbulence. This involves representing the multimaterial Reynolds stress for each material as a turbulent viscosity times the rate of strain based on the mean velocity of that material. The multimaterial turbulent viscosity is related to the fluctuational kinetic energy kappa, and the rate of fluctuational energy dissipation epsilon, for each material. Hence a set of kappa and epsilon equations must be solved, together with mean mass and momentum conservation equations, for each material. Both kappa and the turbulent viscosities enter into the momentum exchange force. The theory is applied to (a) calculation of the drag force on a sphere fixed in a uniform flow, (b) calculation of the settling rate in a suspension and (c) calculation of velocity profiles in the pneumatic transport of solid particles in a pipe.
Kashiwa, B.
Circular Ones Matrices and the Stable Set Polytope of Quasi-Line ...
Circular Ones Matrices and the Stable Set Polytope of Quasi-Line. Graphs. Friedrich Eisenbrand ?. Gianpaolo Oriolo �. Gautier Stauffer �. Paolo Ventura �.
Turbulence-Induced Instabilities in EP and QGP
Polarization properties of turbulent stochastically inhomogeneous ultrarelativistic QED plasma are studied. It is shown that the sign of nonlinear turbulent Landau damping corresponds to an instability of the spacelike modes and, for sufficiently large turbulent fields, to an actual instability of a system.
Martin Kirakosyan; Andrei Leonidov; Berndt Muller
NLE Websites -- All DOE Office Websites (Extended Search)
Jet Fuel from Bio-Diesel Background Due to concerns with limited resources of petroleum-based fuels, the demand for using renewable feedstocks, such as vegetable oils and animal...
Current-driven instability of magnetic jets
MHD instabilities can be responsible for the complex morphology of astrophysical jets. We consider the stability properties of jets containing both the azimuthal and axial field of subthermal strength. The presence of the magnetic field with complex topology in jets is suggested by theoretical models and it is consistent with recent observations. Stability is discussed by means of a linear analysis of the ideal MHD equations.We argue that, in the presence of azimuthal and axial magnetic fields, the jet is always unstable to non-axisymmetric perturbations. Stabilization does not occur even if the strengths of these field components are comparable. If the axial field is weaker than the azimuthal one, instability occurs for perturbations with any azimuthal wave number $m$, and the growth rate reach a saturation value for small values of $m$. If the axial field is stronger than the toroidal one, the instability shows off for perturbations with relatively large $m$.
Bonanno, Alfio
Stochastic Dynamics of the Midlatitude Atmospheric Jet
Science Conference Proceedings (OSTI)
The innate tendency of the background straining field of the midlatitude atmospheric jet to preferentially amplify a subset of disturbances produces a characteristic response to stochastic perturbation whether the perturbations are internally ...
Brian F. Farrell; Peteros J. Ioannou
Developments of the ATLAS Jet Trigger
There have been a lot of recent changes in the ATLAS jet trigger. The standard strategy, based on Regions Of Interest, is not well-suited for multi-jet events since it leads to pathologies and efficiency losses. This philosophy has been changed for the jet trigger, and we now have the possibility of unpacking the full calorimeter at Event Filter and (even for a small subset of the events) at an intermediate level between Level-1 and Level-2. We also moved to the use of calibrated scale at trigger level, and to the application of noise cuts to reduce rate spikes. We will present the performance of the jet trigger in 2011, when most of these changes were operational
Lopes, L; The ATLAS collaboration
Performance of the ATLAS Jet Trigger
There have been a lot of recent changes in the ATLAS jet trigger. The standard strategy, based on Regions Of Interest, is not well-suited for multi-jet events since it leads to pathologies and efficiency losses. This philosophy has been changed for the jet trigger, and we now have the possibility of unpacking the full calorimeter at Event Filter and (even for a small subset of the events) at an intermediate level between Level-1 and Level-2. We also moved to the use of calibrated scale at trigger level, and to the application of noise cuts to reduce rate spikes. We will present the performance of the jet trigger in 2011, when most of these changes were operational
Lopes, L; The ATLAS collaboration
The Initial Composition of Jet Condensation Trails
Science Conference Proceedings (OSTI)
Physicochemical processes that generate and transform aerosols in jet aircraft plumes are discussed on the basis of theoretical models and recent observations of young contrails in the upper troposphere. The initial evolution of optical depth and ...
B. K�rcher; Th Peter; U. M. Biermann; U. Schumann
Persistent Multiple Jets and PV Staircase
Science Conference Proceedings (OSTI)
The persistence of multiple jets is investigated with a quasigeostrophic, two-layer, ?-plane channel model. Linearly unstable normal modes are found to be capable of qualitatively describing the eddy fluxes of the nonlinear model. For a ...
Changhyun Yoo; Sukyoung Lee
Jets (relativistic and non) in astrophysics
Let's take stock of the situation on one of the most studied astrophysical phenomena during the latest years: the jets escaping from protostars, stellar singularities, GRB and active galactic nuclei.
Foschini, Luigi
String model for spinning quark jets
Science Conference Proceedings (OSTI)
A string model of quark hadronization, taking the quark spin degree of freedom into account, is proposed. The method for using the model in a Monte-Carlo code for jet generation is given.
Artru, X.; Belghobsi, Z. [Universite de Lyon, CNRS/IN2P3 and Universite Lyon 1, Institut de Physique Nucleaire de Lyon, Laboratoire de Physique Theorique, Universite de Jijel (Algeria)
Mixing Processes within the Polar Night Jet
Science Conference Proceedings (OSTI)
Lagrangian material line simulations are performed using U.K. Meteorological Office assimilated winds and temperatures to examine mixing processes in the middle- and lower-stratospheric polar night jet during the 1992 Southern Hemisphere spring ...
R. Bradley Pierce; T. Duncan Fairlie; William L. Grose; Richard Swinbank; Alan O'Neill
Internal shocks model for microquasar jets
We present an internal shocks model to investigate particle acceleration and radiation production in microquasar jets. The jet is modelled with discrete ejecta at various time intervals. These ejecta (or 'shells') may have different properties including the bulk velocity. Faster shells can catch up and collide with the slower ones, thus giving rise to shocks. The particles are accelerated inside the shocked plasma. Each collision results in a new shell, which may take part in any subsequent collisions as well as radiate due to synchrotron radiation. Almost continuous energy dissipation along the jet can be obtained with a large number of shell collisions. We investigate the spectral energy distribution of such jets as well as the physical significance of various parameters (e.g. the time interval between ejections and the shell size).
Omar Jamil; Rob Fender; Christian Kaiser
New results on jet fragmentation at CDF
Presented are the latest results of jet fragmentation studies at the Tevatron using the CDF Run II detector. Studies include the distribution of transverse momenta (Kt) of particles jets, two-particle momentum correlations, and indirectly global event shapes in p{bar p} collisions. Results are discussed within the context of recent Next-to-Leading Log calculations as well as earlier experimental results from the Tevatron and e{sup +}e{sup -} colliders.
Jindariani, Sergo; /Florida U.
We argue that dark matter particles which have strong interactions with the Standard Model particles are not excluded by current astrophysical constraints. These dark matter particles have unique signatures at colliders; instead of missing energy, the dark matter particles produce jets. We propose a new search strategy for such strongly interacting particles by looking for a signal of two trackless jets. We show that suitable cuts can plausibly allow us to find these signals at the LHC even in early data.
Bai, Yang; /SLAC; Rajaraman, Arvind; /UC, Irvine
U.S. Exports of Kerosene-Type Jet Fuel (Thousand Barrels per Day)
U.S. Energy Information Administration (EIA)
Kerosene-Type Jet Fuel Exports; Kerosene-Type Jet Fuel Exports by Destination; Kerosene-Type Jet Fuel Supply and Disposition ...
Supersonic Jet Excitation using Flapping Injection
Supersonic jet noise reduction is important for high speed military aircraft. Lower acoustic levels would reduce structural fatigue leading to longer lifetime of the jet aircraft. It is not solely structural aspects which are of importance, health issues of the pilot and the airfield per- sonnel are also very important, as high acoustic levels may result in severe hearing damage. It remains a major challenge to reduce the overall noise levels of the aircraft, where the supersonic exhaust is the main noise source for near ground operation. Fluidic injection into the supersonic jet at the nozzle exhaust has been shown as a promising method for noise reduction. It has been shown to speed up the mix- ing process of the main jet, hence reducing the kinetic energy level of the jet and the power of the total acoustic radiation. Furthermore, the interaction mechanism between the fluidic injection and the shock structure in the jet exhaust plays a crucial role in the total noise radia- tion. In this study, LES is used...
Hafsteinsson, Haukur; Andersson, Niklas; Cuppoletti, Daniel; Gutmark, Ephraim; Prisell, Erik
Final Report for grant DE-FG02-06ER54898. The dynamics and generation of intermittent plasma turbulent structures, widely known as "blobs" have been studied in the presence of sheared plasma flows in a controlled laboratory experiment.
Gilmore, Mark A. [University of New Mexico
Stability of an optical vortex in a circular nematic cell
The stability of an optical vortex in a cell with a circular cross section containing a nematic liquid crystal is studied. A modulation theory based on an averaged Lagrangian formulation is developed to study this stability. It is found that the vortex is stable unless the radius of the cell is very small, nearly the width of the vortex itself. Based on the analysis of a stationary vortex, the stability of a low-amplitude vortex in a large cell under the influence of its orbital angular momentum and the repelling effect of the cell boundary are studied. The predictions of this modulation theory are found to be in excellent agreement with numerical simulations.
Minzoni, Antonmaria A. [Fenomenos Nonlineales y Mecanica (FENOMEC), Departamento de Matematicas y Mecanica, Instituto de Investigacion en Matematicas Aplicadas y Sistemas, Universidad Nacional Autonoma de Mexico, 01000 Mexico D.F. (Mexico); Smyth, Noel F. [School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom); Xu Zhiyong [Nonlinear Physics Center, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)
Federal Acquisition Regulations Federal Acquisition Circular 2005-51 Summary
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
Regulations Regulations Federal Acquisition Circular 2005-51 Summary Federal Register April 1, 2011 76FR 18304 I Women-Owned Small Business (WOSB) Program (Interim Rule). II Clarification of Standard Form 26--Award/Contract. Item I--Women-Owned Small Business (WOSB) Program (FAR Case 2010-015) (Interim) This interim rule amends the FAR to add subpart 19.15, Women-Owned Small Business Program, which will assist Federal agencies in achieving the 5 percent statutory goal for contracting with women-owned small business (WOSB) concerns. Agencies may restrict competition to economically disadvantaged women-owned small business (EDWOSB) concerns for contracts assigned a North American Industry Classification Systems (NAICS) code in an industry in which the Small Business Administration has
Shock wave / turbulent boundary layer interactions
Science Conference Proceedings (OSTI)
This visualization shows the results of the simulation of a Mach 4 flow into two cone nosed cylindrical bodies adjacent to a flat plate. The analysis was computed with a Reynolds Averaged Navier Stokes (RANS) code utilizing a Spalart-Allmaras Turbulent ... Keywords: CFD, blender, raytracing, scientific visualization, visit, volume rendering
Michael A. Matheson; Allan D. Grosvenor; Alexander A. Zheltovodov
Atmospheric Gravity Waves and Aircraft Turbulence Encounters
Science Conference Proceedings (OSTI)
We describe aircraft turbulence-atmospheric gravity wave events which occurred during a 2-day period over the Continental Divide. The waves are observed by two microbarograph networks an each side of the divide and last for several hours at a ...
A. J. Bedard Jr.; F. Canavero; F. Einaudi
Cup Anemometer Behavior in Turbulent Environments
Science Conference Proceedings (OSTI)
The behavior of the cup anemometer rotor in turbulent atmospheric flow is discussed in terms of a general equation of motion. This equates the rate of change s?? of the rotation rate s? of the rotor to a forcing F(s?, h?, w?), which is proportional ...
Leif Kristensen
Chaotic radiation/turbulence interactions in flames
In this paper, the authors present a review of their recent efforts to model chaotic radiation-turbulence interactions in flames. The main focus is to characterize soot volume fraction fluctuations in turbulent diffusion flames, as they strongly contribute to these interaction. The approach is based on the hypothesis that the fluctuations of properties in turbulent flames are deterministic in nature, rather than random. The authors first discuss the theoretical details and then they briefly outline the experiments conducted to measure the scattered light signals from fluctuating soot particles along the axis of an ethylene-air diffusion flame. They compare the power spectra and time series obtained from experiments against the ad-hoc and rigorous models derived using a series of logistic maps. These logistic maps can be used in simulation of the fluctuations in these type of flames, without extensive computational effort or sacrifice of physical detail. Availability of accurate models of these kinds allows investigation of radiation-turbulence interactions at a more fundamental level than it was previously possible.
Menguec, M.P.; McDonough, J.M.
Wavelet Turbulence for Fluid Simulation Theodore Kim
in the running time. We instead propose an algorithm that generates small-scale fluid de- tail procedurally. We of the key results of Kolmogorov the- ory is that the energy spectrum of a turbulent fluid approaches a five spectra [Perrier et al. 1995], and the sub- stitution is common in fluid dynamics [Farge et al. 1996
California at Santa Barbara, University of
Inertial range turbulence in kinetic plasmas
The transfer of turbulent energy through an inertial range from the driving scale to dissipative scales in a kinetic plasma followed by the conversion of this energy into heat is a fundamental plasma physics process. A theoretical foundation for the study of this process is constructed, but the details of the kinetic cascade are not well understood. Several important properties are identified: (a) the conservation of a generalized energy by the cascade; (b) the need for collisions to increase entropy and realize irreversible plasma heating; and (c) the key role played by the entropy cascade--a dual cascade of energy to small scales in both physical and velocity space--to convert ultimately the turbulent energy into heat. A strategy for nonlinear numerical simulations of kinetic turbulence is outlined. Initial numerical results are consistent with the operation of the entropy cascade. Inertial range turbulence arises in a broad range of space and astrophysical plasmas and may play an important role in the ther...
Howes, G G
Inertial range turbulence in kinetic plasmas
The transfer of turbulent energy through an inertial range from the driving scale to dissipative scales in a kinetic plasma followed by the conversion of this energy into heat is a fundamental plasma physics process. A theoretical foundation for the study of this process is constructed, but the details of the kinetic cascade are not well understood. Several important properties are identified: (a) the conservation of a generalized energy by the cascade; (b) the need for collisions to increase entropy and realize irreversible plasma heating; and (c) the key role played by the entropy cascade--a dual cascade of energy to small scales in both physical and velocity space--to convert ultimately the turbulent energy into heat. A strategy for nonlinear numerical simulations of kinetic turbulence is outlined. Initial numerical results are consistent with the operation of the entropy cascade. Inertial range turbulence arises in a broad range of space and astrophysical plasmas and may play an important role in the thermalization of fusion energy in burning plasmas.
G. G. Howes
Premixed turbulent combustion to opposed streams
Premixed turbulent combustion in opposed streams has been studied experimentally by the use of two component laser doppler aneomometry. This flow geometry is part of a class of stagnating flows used to study turbulent combustion in recent years. It does not involve any surface near the flames because of the flow symmetry thus circumventing many of the effects of flame surface interaction. The mean non-reacting flow is found to be self-similar for all the conditions studied in this and the stagnation plate configuration. A homogeneous region of plane straining is produced in the vicinity of the stagnation and there is a strong interaction between the turbulence in the flow and the mean straining which can increase the rms velocity as the flow stagnates. The reacting flow fields are found to be symmetric about the free stagnation point. The traverses of mean axial velocity in the stagnation streamlines for reaction flows are not dramatically different from the non-reaction flows. These results differ from turbulent combustion experiments where the flow is stagnated by a flat plate. The extinction limits was studied for propane:air mixtures. 11 refs.
Kostiuk, L.W.; Cheng, R.K.
On Challenges for Hypersonic Turbulent Simulations
This short note discusses some of the challenges for design of suitable spatial numerical schemes for hypersonic turbulent flows, including combustion, and thermal and chemical nonequilibrium flows. Often, hypersonic turbulent flows in re-entry space vehicles and space physics involve mixed steady strong shocks and turbulence with unsteady shocklets. Material mixing in combustion poses additional computational challenges. Proper control of numerical dissipation in numerical methods beyond the standard shock-capturing dissipation at discontinuities is an essential element for accurate and stable simulations of the subject physics. On one hand, the physics of strong steady shocks and unsteady turbulence/shocklet interactions under the nonequilibrium environment is not well understood. On the other hand, standard and newly developed high order accurate (fourth-order or higher) schemes were developed for homogeneous hyperbolic conservation laws and mixed hyperbolic and parabolic partial differential equations (PDEs) (without source terms). The majority of finite rate chemistry and thermal nonequilibrium simulations employ methods for homogeneous time-dependent PDEs with a pointwise evaluation of the source terms. The pointwise evaluation of the source term might not be the best choice for stability, accuracy and minimization of spurious numerics for the overall scheme.
Yee, H C; Sjogreen, B
Turbulence Characteristics in a Tidal Channel
Science Conference Proceedings (OSTI)
A broadband ADCP and a moored microstructure instrument (TAMI) were deployed in a tidal channel of 30-m depth and with peak speeds of 1 m s?1. The measurements enable us to derive profiles of stress, turbulent kinetic energy (TKE), the rate of ...
Youyu Lu; Rolf G. Lueck; Daiyan Huang
LES algorithm for turbulent reactive flows simulation
Science Conference Proceedings (OSTI)
The paper presents the development and implementation of a Large Eddy Simulation numerical algorithm for simulating turbulent reactive flows. The numerical algorithm is based on a 5 step modified Runge - Kutta numerical scheme with a dual time stepping ... Keywords: Runge - Kutta numerical scheme, large eddy simulation, linear eddy model
Ionut Porumbel; Cristian C�rl?nescu; Florin Gabriel Florean; Constantin Eusebiu Hritcu
Jet energy scale determination in the D0 experiment
The calibration of jet energy measured in the \\DZero detector is presented, based on ppbar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. Jet energies are measured using a sampling calorimeter composed of uranium and liquid argon as the passive and active media, respectively. This paper describes the energy calibration of jets performed with photon+jet, Z+jet and dijet{} events, with jet transverse momentum pT > 6 GeV and pseudorapidity range |eta| energy in simulation and in particular of the effects due to the flavor of the parton originating the jet, correcting biases up to 3%-4% in jets with low pT originating from gluons and up to 6%-8% in jets from b quarks.
D0 Collaboration
AIAA Paper 2006-0102 Analysis of Jet Effects on Co-Flow Jet Airfoil
.-C. Zha, C. Paxton, A. Conley, A. Wells, and B. Carroll, "Effect of Injection Slot Size on High in this paper to analyze the jet effect on co-flow jet airfoil with injection and suction and the airfoil with injection only. The ducts reaction forces formulations to be included for lift and drag calculation
Zha, Gecheng
Compressible Turbulence and Interactions with Shock Waves and Material
NLE Websites -- All DOE Office Websites (Extended Search)
Compressible Turbulence Compressible Turbulence and Interactions with Shock Waves and Material Interfaces Compressible Turbulence and Interactions with Shock Waves and Material Interfaces Lele.jpg Alternate Title: High-fidelity simulations of supersonic turbulent mixing and combustion Key Challenges: Direct numerical simulation (DNS) of isotropic turbulence interacting with a normal shock wave and turbulent multi-material mixing in the Richtmyer-Meshkov instability (RMI) Why it Matters: Shock/turbulence interaction is a fundamental phenomenon in fluid mechanics that occurs in a wide range of interesting problems in various disciplines, including supernova explosions, inertial confinement fusion, hypersonic flight and propulsion, and shock wave lithotripsy. Accomplishments: A novel solution-adaptive algorithm that applies different
Petascale Direct Numerical Simulations of Turbulent Channel Flow
NLE Websites -- All DOE Office Websites (Extended Search)
Petascale Petascale Direct Numerical Simulations of Turbulent Channel Flow MyoungKyu Lee firstname.lastname@example.com Department of Mechanical Engineering University of Texas at Austin ESP Meeting May, 2013 M.K. Lee (Univ of Texas, Austin) Petascale DNS of Turbulent Channel Flow ESP Meeting May, 2013 1 / 30 Contents Project Overview Performance Optimization Early Result Conclusion M.K. Lee (Univ of Texas, Austin) Petascale DNS of Turbulent Channel Flow ESP Meeting May, 2013 2 / 30 Project Overview Project Title ◮ Petascale Direct Numerical Simulations of Turbulent Channel Flow Goal ◮ Expanding our understand of wall-bounded turbulence Personnel ◮ P.I. : Robert Moser ◮ Primary Developer : M.K.Lee ◮ Software Engineering Support : Nicholas Malaya ◮ Catalyst : Ramesh Balakrishnan M.K. Lee (Univ of Texas, Austin) Petascale DNS of Turbulent Channel Flow ESP Meeting May, 2013 3 / 30 Turbulent
Science Conference Proceedings (OSTI)
While rotating visual and auditory stimuli have long been known to elicit self-motion illusions (�circular vection�), audiovisual interactions have hardly been investigated. Here, two experiments investigated whether visually induced circular ... Keywords: Audiovisual interactions, presence, psychophysics, self-motion simulation, spatial sound, vection, virtual reality
Bernhard E. Riecke; Aleksander V�ljam�e; J�rg Schulte-Pelkum
Science Conference Proceedings (OSTI)
The possibility of studying compressible turbulent flows using gas targets driven by high power lasers and diagnosed with optical techniques is investigated. The potential advantage over typical laser experiments that use solid targets and x-ray diagnostics is more detailed information over a larger range of spatial scales. An experimental system is described to study shock - jet interactions at high Mach number. This consists of a mini-chamber full of nitrogen at a pressure {approx} 1 atms. The mini-chamber is situated inside a much larger vacuum chamber. An intense laser pulse ({approx}100J in {approx} 5ns) is focused on to a thin {approx} 0.3{micro}m thick silicon nitride window at one end of the mini-chamber. The window acts both as a vacuum barrier, and laser entrance hole. The ''explosion'' caused by the deposition of the laser energy just inside the window drives a strong blast wave out into the nitrogen atmosphere. The spherical shock expands and interacts with a jet of xenon introduced though the top of the mini-chamber. The Mach number of the interaction is controlled by the separation of the jet from the explosion. The resulting flow is visualized using an optical schlieren system using a pulsed laser source at a wavelength of 0.53 {micro}m. The technical path leading up to the design of this experiment is presented, and future prospects briefly considered. Lack of laser time in the final year of the project severely limited experimental results obtained using the new apparatus.
Edwards, M J; Hansen, J; Miles, A R; Froula, D; Gregori, G; Glenzer, S; Edens, A; Dittmire, T
Interaction of Nocturnal Low-Level Jets with Urban Geometries as seen in Joint URBAN 2003 Data
The nocturnal low-level jet (LLJ) is a well-documented phenomenon world-wide, especially in the southern Great Plains of the United States (Bonner 1968, Whiteman et al. 1997, Banta et al., 2002) where it contributes to severe weather. In the canonical rural case, the nocturnal LLJ forms as the release of daytime convective turbulent stresses allow nighttime winds above a stable boundary layer to accelerate to supergeostrophic wind speeds. In situations with surface winds of less than 5 m/s, wind speeds at altitudes of 100m due to the nocturnal LLJ can be greater than 20 m/s. The turbulence generated by this wind shear can induce nocturnal mixing events and control surface-atmosphere exchange, thereby affecting atmospheric transport and dispersion. The Joint URBAN 2003 urban dispersion dataset, collected in Oklahoma City in July, 2003, includes several occurrences of strong LLJs, thereby providing a unique opportunity to document how the LLJ interacts with the complexity of urban geometries and to explore the significance of LLJs for transport and dispersion in urban environments. Based on this dataset, we will answer the following questions: (1) How often do LLJs occur during the experiment? (2) How does the increase in surface roughness represented by the city center, as compared to the rural environment, affect the altitude and speed of the jet, based on data from upwind and downwind wind profiles? (3) How often do LLJs contribute to nocturnal mixing events within the Oklahoma City urban area, as observed in profiles of turbulence quantities at an 80m pseudo-tower located 750m downwind of Oklahoma City center? (4) Can the effect of these LLJ-induced mixing events be identified in the dispersion datasets?
Lundquist, J K
Modern theoretical models of astrophysical jets combine accretion, rotation, and magnetic fields to launch and collimate supersonic flows from a central source. Near the source, magnetic field strengths must be large enough to collimate the jet requiring that the Poynting flux exceeds the kinetic energy flux. The extent to which the Poynting flux dominates kinetic energy flux at large distances from the engine distinguishes two classes of models. In magneto-centrifugal launch models, magnetic fields dominate only at scales {approx}< 100 engine radii, after which the jets become hydrodynamically dominated (HD). By contrast, in Poynting flux dominated (PFD) magnetic tower models, the field dominates even out to much larger scales. To compare the large distance propagation differences of these two paradigms, we perform three-dimensional ideal magnetohydrodynamic adaptive mesh refinement simulations of both HD and PFD stellar jets formed via the same energy flux. We also compare how thermal energy losses and rotation of the jet base affects the stability in these jets. For the conditions described, we show that PFD and HD exhibit observationally distinguishable features: PFD jets are lighter, slower, and less stable than HD jets. Unlike HD jets, PFD jets develop current-driven instabilities that are exacerbated as cooling and rotation increase, resulting in jets that are clumpier than those in the HD limit. Our PFD jet simulations also resemble the magnetic towers that have been recently created in laboratory astrophysical jet experiments.
Huarte-Espinosa, M.; Frank, A.; Blackman, E. G. [Department of Physics and Astronomy, University of Rochester, 600 Wilson Boulevard, Rochester, NY 14627-0171 (United States); Ciardi, A. [LERMA, Universite Pierre et Marie Curie, Observatoire de Paris, F-92195 Meudon (France); Hartigan, P. [Department of Physics and Astronomy, Rice University, 6100 S. Main, Houston, TX 77521-1892 (United States); Lebedev, S. V.; Chittenden, J. P. [Blackett Laboratory, Imperial College London, SW7 2BW London (United Kingdom)
High energy emission from galactic jets
In this chapter we review some aspects of X-ray binaries, particularly those presenting steady jets, i.e. microquasars. Because of their proximity and similarities with active galactic nuclei (AGN), galactic jet sources are unique laboratories to test astrophysical theories of a universal scope. Due to recent observational progress made with the new generation of gamma-ray imaging atmospheric Cherenkov telescopes and in view of the upcoming km3-size neutrino detectors, we focus especially on the possible high-energy gamma radiation and neutrino emission. In connection with this, we also comment about astrophysical jets present in young stellar objects, and we briefly discuss similarities and differences with extragalactic AGN and gamma-ray bursters.
H. R. Christiansen
Jet physics from static charges in AdS space
Soft interactions with high-energy jets are explored in radial coordinates which exploit the approximately conformal behavior of perturbative gauge theories. In these coordinates, the jets, approximated by Wilson lines, ...
Stewart, Iain
Formation of Jets and Equatorial Superrotation on Jupiter
Science Conference Proceedings (OSTI)
The zonal flow in Jupiter�s upper troposphere is organized into alternating retrograde and prograde jets, with a prograde (superrotating) jet at the equator. Existing models posit as the driver of the flow either differential radiative heating of ...
Tapio Schneider; Junjun Liu
The Dynamical Relationship between Subtropical and Eddy-Driven Jets
Science Conference Proceedings (OSTI)
This study examines the impact of a subtropical jet on the development of baroclinic waves and polar-front jets with an idealized multilevel primitive equation model. Linear stability analysis and initial-value approaches suggest that baroclinic ...
Sukyoung Lee; Hyun-kyung Kim
Recirculation Gyres Forced by a Beta-Plane Jet
Science Conference Proceedings (OSTI)
A numerical model, with quasigeostrophic and barotropic dynamics, is used to study the forcing of mean flows by an unstable jet. The initially zonal jet has specified shape and transport at the western inflow boundary and is sufficiently intense ...
Steven R. Jayne; Nelson G. Hogg; Paola Malanotte-Rizzoli
Jet Jumping: Low-Frequency Variability in the Southern Ocean
Science Conference Proceedings (OSTI)
The authors study intrinsic variability in the position of jets in a ?-plane channel ocean with simple topography using a quasigeostrophic numerical model. This study links the variability in jet position with abyssal anticyclones that form as a ...
Christopher C. Chapman; Andrew McC. Hogg
Optimized Parameters for a Mercury Jet Target
Science Conference Proceedings (OSTI)
A study of target parameters for a high-power, liquid mercury jet target system for a neutrino factory or muon collider is presented. Using the MARS code, we simulate particle production initiated by incoming protons with kinetic energies between 2 and 100 GeV. For each proton beam energy, we maximize production by varying the geometric parameters of the target: the mercury jet radius, the incoming proton beam angle, and the crossing angle between the mercury jet and the proton beam. The number of muons surviving through an ionization cooling channel is determined as a function of the proton beam energy. We optimize the mercury jet target parameters: the mercury jet radius, the incoming proton beam angle and the crossing angle between the mercury jet and the proton beam for each proton beam energy. The optimized target radius varies from about 0.4 cm to 0.6 cm as the proton beam energy increases. The optimized beam angle varies from 75 mrad to 120 mrad. The optimized crossing angle is near 20 mrad for energies above 5 GeV. These values differ from earlier choices of 67 mrad for the beam angle and 33 mrad for the crossing angle. These new choices for the beam parameters increase the meson production by about 20% compared to the earlier parameters. Our study demonstrates that the maximum meson production efficiency per unit proton beam power occurs when the proton kinetic energy is in the range of 5-15 GeV. Finally, the dependence on energy of the number of muons at the end of the cooling channel is nearly identical to the dependence on energy of the meson production 50 m from the target. This demonstrates that the target parameters can be optimized without the additional step of running the distribution through a code such as ICOOL that simulates the bunching, phase rotation, and cooling.
Ding, X.; Kirk, H.
Causality detection and turbulence in fusion plasmas
This work explores the potential of an information-theoretical causality detection method for unraveling the relation between fluctuating variables in complex nonlinear systems. The method is tested on some simple though nonlinear models, and guidelines for the choice of analysis parameters are established. Then, measurements from magnetically confined fusion plasmas are analyzed. The selected data bear relevance to the all-important spontaneous confinement transitions often observed in fusion plasmas, fundamental for the design of an economically attractive fusion reactor. It is shown how the present method is capable of clarifying the interaction between fluctuating quantities such as the turbulence amplitude, turbulent flux, and Zonal Flow amplitude, and uncovers several interactions that were missed by traditional methods.
van Milligen, B Ph; Ramisch, M; Estrada, T; Hidalgo, C; Alonso, A
Cosmic ray propagation in galactic turbulence
We revisit propagation of galactic cosmic rays in light of recent advances in cosmic ray diffusion theory in realistic interstellar turbulence. We use tested model of turbulence in which it has been shown that fast modes dominate scattering of cosmic rays. As a result, propagation becomes inhomogeneous and environment dependent. By adopting the formalism of the nonlinear theory (NLT) developed by Yan & Lazarian (2008), we calculate diffusion of cosmic rays self-consistently from first principles. We assume a two-phase model for the Galaxy to account for different damping mechanisms of the fast modes, and we find that the energy dependence of the diffusion coefficient is mainly affected by medium properties. We show that it gives a correct framework to interpret some of the recent CR puzzles.
Evoli, Carmelo
Turbulence in the Molecular Interstellar Medium
Abstract. The observational record of turbulence within the molecular gas phase of the interstellar medium is summarized. We briefly review the analysis methods used to recover the velocity structure function from spectroscopic imaging and the application of these tools on sets of cloud data. These studies identify a near-invariant velocity structure function that is independent of local the environment and star formation activity. Such universality accounts for the cloud-to-cloud scaling law between the global line-width and size of molecular clouds found by Larson (1981) and constrains the degree to which supersonic turbulence can regulate star formation. In addition, the evidence for large scale driving sources necessary to sustain supersonic flows is summarized.
Mark H. Heyer; Chris Brunt
Gauge/gravity duality and jets in strongly coupled plasma
We discuss jets in strongly coupled N = 4 supersymmetric Yang-Mills plasma and their dual gravitational description.
Chesler, Paul M
Gauge/gravity duality and jets in strongly coupled plasma
We discuss jets in strongly coupled N = 4 supersymmetric Yang-Mills plasma and their dual gravitational description.
Paul M. Chesler
Jets and the hadronic final state at HERA
Recent results on jets and the hadronic final state from the HERA collaborations H1 and ZEUS are reviewed.
T. Schoerner-Sadenius
Michigan Refinery Catalytic Hydrotreating, Kerosene/Jet Fuel ...
U.S. Energy Information Administration (EIA)
Cat. Hydro.. Kerosene/Jet Fuel Downstream Charge Capacity (B/SD) Michigan Downstream Charge Capacity of Operable Petroleum Refineries ...
Puerto Rico Refinery Catalytic Hydrotreating, Kerosene/Jet Fuel ...
U.S. Energy Information Administration (EIA)
Puerto Rico Refinery Catalytic Hydrotreating, Kerosene/Jet Fuel Downstream Charge Capacity as of January 1 (Barrels per Stream Day)
On the Counter-jet Emission in GRB Afterglows
Science Conference Proceedings (OSTI)
We investigate the dynamical evolution of double-sided jets and present detailed numerical studies on the emission from the receding jet of gamma-ray bursts. It is found that the receding jet emission is generally very weak and only manifests as a plateau in the late time radio afterglow light curves. Additionally, we find that the effect of synchrotron self-absorption can influence the peak time of the receding jet emission significantly.
Wang Xin; Huang, Y. F. [Department of Astronomy, Nanjing University, Nanjing 210093 (China)
Photon - Jet Correlations and Constraints on Fragmentation Functions
We study the production of a large-pT photon in association with a jet in proton-proton collisions. We examine the sensitivity of the jet rapidity distribution to the gluon distribution function in the proton. We then assess the sensitivity of various photon + jet correlation observables to the photon fragmentation functions. We argue that RHIC data on photon-jet correlations can be used to constrain the photon fragmentation functions in a region which was barely accessible in LEP experiments.
Z. Belghobsi; M. Fontannaz; J. -Ph. Guillet; G. Heinrich; E. Pilon; M. Werlen
Centrifugally driven electrostatic instability in extragalactic jets
The stability problem of the rotation-induced electrostatic wave in extragalactic jets is presented. Solving a set of equations describing dynamics of a relativistic plasma flow of active galactic nuclei (AGN) jets, an expression of the instability rate has been derived and analyzed for typical values of AGNs. The growth rate was studied versus the wavelength and the inclination angle and it has been found that the instability process is very efficient with respect to the accretion disk evolution, indicating high efficiency of the instability.
Osmanov, Z. [Georgian National Astrophysical Observatory, Kazbegi ave. 2a, Tbilisi 0160 (Georgia)
The Cambridge Jet algorithm: features and applications
Jet clustering algorithms are widely used to analyse hadronic events in high energy collisions. Recently a new clustering method, known as `Cambridge', has been introduced. In this article we present an algorithm to determine the transition values of y_cut for this clustering scheme, which allows to resolve any event to a definite number of jets in the final state. We discuss some particularities of the Cambridge clustering method and compare its performance to the Durham clustering scheme for Monte Carlo generated e+e- annihilation events.
Stan Bentvelsen; Irmtraud Meyer
High pressure water jet mining machine
A high pressure water jet mining machine for the longwall mining of coal is described. The machine is generally in the shape of a plowshare and is advanced in the direction in which the coal is cut. The machine has mounted thereon a plurality of nozzle modules each containing a high pressure water jet nozzle disposed to oscillate in a particular plane. The nozzle modules are oriented to cut in vertical and horizontal planes on the leading edge of the machine and the coal so cut is cleaved off by the wedge-shaped body.
Barker, Clark R. (Rolla, MO)
Enhancement of wall jet transport properties
By enhancing the natural instabilities in the boundary layer and in the free shear layer of a wall jet, the boundary is minimized thereby increasing the transport of heat and mass. Enhancing the natural instabilities is accomplished by pulsing the flow of air that creates the wall jet. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct.
Claunch, Scott D. (Broomfield, CO); Farrington, Robert B. (Golden, CO)
Gamma-Ray Bursts: Jets and Energetics
The relativistic outflows from gamma-ray bursts are now thought to be narrowly collimated into jets. After correcting for this jet geometry there is a remarkable constancy of both the energy radiated by the burst and the kinetic energy carried by the outflow. Gamma-ray bursts are still the most luminous explosions in the Universe, but they release energies that are comparable to supernovae. The diversity of cosmic explosions appears to be governed by the fraction of energy that is coupled to ultra-relativistic ejecta.
D. A. Frail
Gravity waves from vortex dipoles and jets
The dissertation first investigates gravity wave generation and propagation from jets within idealized vortex dipoles using a nonhydrostatic mesoscale model. Several initially balanced and localized jets induced by vortex dipoles are examined here. Within these dipoles, inertia-gravity waves with intrinsic frequencies 1-2 times the Coriolis parameter are simulated in the jet exit region. The ray tracing analysis reveals strong variation of wave characteristics along ray paths. The dependence of wave amplitude on the Rossby number is examined through experiments in which the two vortices are initially separated by a large distance but subsequently approach each other and form a vortex dipole with an associated amplifying localized jet. The amplitude of stationary gravity waves in the simulations with a 90-km grid spacing increases nearly linearly with the square of the Rossby number but significantly more rapidly when smaller grid spacing is used. To further address the source mechanism of the gravity waves within the vortex dipole, a linear numerical framework is developed based on the framework proposed by Plougonven and Zhang (2007). Using the nonlinearly balanced fields as the basic state and driven by three types of large scale forcing, the vorticity, divergence and thermodynamic forcing, this linear model is utilized to obtain linear wave responses. The wave packets in the linear responses compare reasonably well with the MM5 simulated gravity waves. It is suggested that the vorticity forcing is the leading contribution to both gravity waves in the jet exit region and the ascent/descent feature in the jet core. This linear model is also adopted to study inertia-gravity waves in the vicinity of a baroclinic jet during the life cycle of an idealized baroclinic wave. It is found that the thermodynamic forcing and the vorticity forcing are equally important to the gravity waves in the low stratosphere, but the divergence forcing is again playing a lesser role. Two groups of wave packets are present in the linear responses; their sources appear to locate either near the surface front or near the middle/upper tropospheric jet.
Wang, Shuguang
Displacement speeds in turbulent premixed flame simulations
The theory of turbulent premixed flames is based on acharacterization of the flame as a discontinuous surface propagatingthrough the fluid. The displacement speed, defined as the local speed ofthe flame front normal to itself, relative to the unburned fluid,provides one characterization of the burning velocity. In this paper, weintroduce a geometric approach to computing displacement speed anddiscuss the efficacy of the displacement speed for characterizing aturbulent flame.
Day, Marcus S.; Shepherd, Ian G.; Bell, J.; Grcar, Joseph F.; Lijewski, Michael J.
Evaluation of Fish-Injury Mechanisms During Exposure to a High-Velocity Jet
As part of the research supported by U.S. Department of Energy (DOE) Advanced Hydropower Turbine System (AHTS) Program, the Pacific Northwest National Laboratory (PNNL) conducted a study where age-0 and age-1 chinook salmon, as well as several other types of fish, were released into a submerged water jet to quantify injuries caused by shear stresses and turbulence (Neitzel et al. 2000). The fish releases were videotaped. These videotape records were digitized and analyzed using new methods to identify the injury mechanisms and the stresses involved. Visible external injuries sustained by fish in this study generally occurred during the initial contact with the jet and not during the tumbling that occurred after the fish fully entered the turbulent flow. The inertial stresses of tumbling, however, may cause temporary or even permanent vestibular and neurological injuries. Such injuries can result in disorientation and loss of equilibrium, which are life threatening in the ''natural'' environment. Operculum injuries predominated at moderate water jet speeds (12 and 15 m {center_dot} s{sup -1}). At the highest speed, eye, operculum, isthmus, and gill injuries were equally common, and disorientation was most common. Bruising and descaling were relatively rare, especially for age-0 fish. Age-0 fish were less susceptible than the larger age-1 fish to all visible injury types, especially at lower speeds. This is presumably because age-0 fish have less mass and inertia, and therefore sustain smaller forces on exposed organs during acceleration. Alternatively, age-0 fish were substantially more susceptible to behavioral impairments such as disorientation. This may also relate to the smaller mass of the age-0 fish. The less massive age-0 fish sustain larger accelerations and jerks, which may be important sources of the internal injuries to the vestibular and neurological systems. All the dynamic parameters computed from the bulk motion of the fish (velocity, jerk, and force) were positively correlated with injury level, based on the results of this study. Multinomial response model results further suggested that force is most predictive of injury.
Guensch, Greg R.; Mueller, Robert P.; McKinstry, Craig A.; Dauble, Dennis D.
Closure in Turbulence from first principles
It has been recently demonstrated, [3], that according to the principle of release of constraints, absence of shear stresses in the Euler equations must be compensated by additional degrees of freedom, and that led to a Reynolds-type enlarged Euler equations (EE equations) with a doublevalued velocity field that do not require any closures. In the first part of the paper, the theory is applies to turbulent mixing and illustrated by propagation of mixing zone triggered by a tangential jump of velocity. A comparison of the proposed solution with the Prandtl's solutions is performed and discussed. In the second part of the paper, a semi-viscose version of the Navier-Stokes equations is introduced. The model does not require any closures since the number of equations is equal to the number of unknowns. Special attention is paid to transition from laminar to turbulent state. The analytical solution for this transition demonstrates the turbulent mean velocity profile that qualitatively similar to the celebrated logarithmic law.
Michail Zak
Universal equations and constants of turbulent motion
This paper presents a parameter-free theory of shear-generated turbulence at asymptotically high Reynolds numbers in incompressible fluids. It is based on a two-fluids concept. Both components are materially identical and inviscid. The first component is an ensemble of quasi-rigid dipole-vortex tubes as quasi-particles in chaotic motion. The second is a superfluid performing evasive motions between the tubes. The local dipole motions follow Helmholtz' law. The vortex radii scale with the energy-containing length scale. Collisions between quasi-particles lead either to annihilation (likewise rotation, turbulent dissipation) or to scattering (counterrotation, turbulent diffusion). There are analogies with birth and death processes of population dynamics and their master equations. For free homogeneous decay the theory predicts the TKE to follow 1/t. With an adiabatic condition at the wall it predicts the logarithmic law with von Karman's constant as 1/\\sqrt{2 pi} = 0.399. Likewise rotating couples form dissipative patches almost at rest ($\\rightarrow$ intermittency) wherein the spectrum evolves like an "Apollonian gear" as discussed first by Herrmann, 1990. On this basis the prefactor of the 3D-wavenumber spectrum is predicted as (1/3)(4 pi)^{2/3}=1.8; in the Lagrangian frequency spectrum it is simply 2. The results are situated well within the scatter range of observational, experimental and DNS results.
Helmut Z. Baumert
Coherent and turbulent fluctuations in TFTR
Classification of the sawteeth observed in the TFTR tokamak has been carried out to highlight the differences between the many types observed. Three types of sawteeth are discussed: ''simple,'' ''small,'' and ''compound.'' During the enhanced confinement discharges on TFTR, sawteeth related to q = 1 are usually not present, but a sawtooth-like event is sometimes observed. ..beta.. approaches the Troyon limit only at low q/sub cyl/ with a clear reduction of achievable ..beta../sub n/ at high q/sub cyl/. This suggests that a ..beta../sub p/ limit, rather than the Troyon-Gruber limit, applies at high q/sub cyl/ in the enhanced confinement discharges. These discharges also reach the stability boundary for n ..-->.. infinity ideal MHD ballooning modes. Turbulence measurements in the scrape-off region with Langmuir and magnetic probes show strong edge density turbulence n-tilde/n = 0.3 - 0.5, with weak magnetic turbulence B-tilde/sub theta/B/sub theta/ > 5 x 10/sup -6/ measured at the wall, but these measurements are very sensitive to local edge conditions.
McGuire, K.; Arunasalam, V.; Bell, M.G.; Bitter, M.; Blanchard, W.R.; Bretz, N.L.; Budny, R.; Bush, C.E.; Callen, J.D.; Chance, M.
The Statistics of Supersonic Isothermal Turbulence
We present results of large-scale three-dimensional simulations of supersonic Euler turbulence with the piecewise parabolic method (PPM) and multiple grid resolutions up to 2048^3 points. Our numerical experiments describe non-magnetized driven turbulent flows with an isothermal equation of state and an rms Mach number of 6. We discuss numerical resolution issues and demonstrate convergence, in a statistical sense, of the inertial range dynamics in simulations on grids larger than 512^3 points. The simulations allowed us to measure the absolute velocity scaling exponents for the first time. The inertial range velocity scaling in this strongly compressible regime deviates substantially from the incompressible Kolmogorov laws. The slope of the velocity power spectrum, for instance, is -1.95 compared to -5/3 in the incompressible case. The exponent of the third-order velocity structure function is 1.28, while in incompressible turbulence it is known to be unity. We propose a natural extension of Kolmogorov's phe...
Kritsuk, Alexei G; Padoan, Paolo; Wagner, Rick
Jet impact on a soap film Geoffroy Kirstetter, Christophe Raufaste,
of the micro-jet or con- versely on its destabilization through the control of the liquid jet atomization, such as impacts, have recently raised some interest and uses for sound absorp- tion or bomb explosion safety [15 can be used to guide and control the jet direction. In the second one, a new class of flow is reported
Paris-Sud XI, Université de
Jet pump feeds corrosion inhibitor in Russian waterflood
The Russian company Orenburgneft JSC tested a proportioning jet pump for injecting corrosion inhibitor into the water injection system at its Tananykskoye waterflood. The jet pump has no moving parts and, therefore, provides an hermetic system with zero emissions of pumped and working fluid. This pump reduces weight, dimensions, and costs compared to mechanical pumps. The paper describes jet pumping and the pump design.
Yuden, I.S. [JKX Oil and Gas, Guildford (United Kingdom); Sazanov, Y.A.; Yeliseev, V.N.; Malov, B.A. [Orenburgneft JSC, Moscow (Russian Federation)
Film cooling effectiveness on a gas turbine blade tip on the near tip pressure side and on the squealer cavity floor is investigated. Optimal arrangement of film cooling holes, effect of a full squealer and a cutback squealer, varying blowing ratios and squealer cavity depth are also examined on film cooling effectiveness. The film-cooling effectiveness distributions are measured on the blade tip, near tip pressure side and the inner pressure and suction side rim walls using a Pressure Sensitive Paint (PSP) technique. A blowing ratio of 1.0 is found to give best results on the pressure side whereas the other tip surfaces give best results for blowing ratios of 2. Film cooling effectiveness tests are also performed on the span of a fully-cooled high pressure turbine blade in a 5 bladed linear cascade using the PSP technique. Film cooling effectiveness over the entire blade region is determined from full coverage film cooling, showerhead cooling and from each individual row with and without an upstream wake. The effect of superposition of film cooling effectiveness from each individual row is then compared with full coverage film cooling. Results show that an upstream wake can result in lower film cooling effectiveness on the blade. Effectiveness magnitudes from superposition of effectiveness data from individual rows are comparable with that from full coverage film cooling. Internal heat transfer measurements are also performed in a high aspect ratio channel and from jet array impingement on a turbulated target wall at large Reynolds numbers. For the channel, three dimple and one discrete rib configurations are tested on one of the wide walls for Reynolds numbers up to 1.3 million. The presence of a turbulated wall and its effect on heat transfer enhancement against a smooth surface is investigated. Heat transfer enhancement is found to decrease at high Re with the discrete rib configurations providing the best enhancement but highest pressure losses. Experiments to investigate heat transfer and pressure loss from jet array impingement are also performed on the target wall at Reynolds numbers up to 450,000. The heat transfer from a turbulated target wall and two jet plates is investigated. A target wall with short pins provides the best heat transfer with the dimpled target wall giving the lowest heat transfer among the three geometries studied.
Mhetras, Shantanu
Studying Z/gamma*+Jet Production
The production of jets in association with a Z/{gamma}* boson is an example of an important class of processes at hadron colliders, namely vector boson + jet (V + jet) production. Comparisons of measurements of this class of processes with theory predictions constitute an important, fundamental test of the Standard Model of particle physics, and of the theory of QCD in particular. While having a smaller cross section than other V +jet processes, Z/{gamma}*({yields} e{sup +}e{sup -}) + jets production, with Z/{gamma}* {yields} e{sup +}e{sup -}/{mu}{sup +}{mu}{sup -}, has a distinct experimental signature allowing for measurements characterized by low backgrounds and a direct, precise measurement of the properties of the decay products of the Z/{gamma}* boson. In this thesis, several new measurements of the properties of jets produced in association with a Z/{gamma}* boson in p{bar p} collisions at {radical}s = 1.96 TeV are presented. The cross section for Z/{gamma}*({yields} e{sup +}e{sup -}) + N jet production (N {le} 3) is measured, differential in the transverse momentum of the Nth jet in the event, normalized to the inclusive Z/{gamma}* cross section. Also, the cross section for Z/{gamma}*({yields} e{sup +}e{sup -}) + N jets (N {ge} 1) is measured, differential in the difference in azimuthal angle between the di-electron system and any jet in the event, normalized to unity. The data used in the measurements were collected by the D0 experiment located at the Tevatron Collider of the Fermi National Accelerator Laboratory and correspond to an integrated luminosity of 1.04 fb{sup -1}. The measured jet transverse momentum spectra are compared with the predictions of perturbative calculations at the next-to-leading order in the strong coupling constant. Given the low sensitivity of the calculations to model parameters, these comparisons represent a stringent test of perturbative QCD. One of the main goals currently being pursued in particle physics is the discovery of the only particle predicted by the Standard Model which has so far no been detected experimentally, namely the Higgs boson. It is assumed that the ATLAS and CMS experiments located at the Large Hadron Collider (LHC), a proton-proton collider at {radical}s = 14 TeV, will be able to detect the Higgs boson, or rule out its existence, within the next few years. The collisions delivered by the LHC will also be used to perform a long range of searches for other new particles, for instance particles predicted by models based on the principle of supersymmetry. The associated production of vector bosons with jets has relatively large production rates at the LHC and can produce a long list of different final states which can include charged leptons, missing transverse energy, as well as light- and heavy-flavour jets. This makes V + jet production a major source of background events to many searches for new particles. Most techniques used for estimating the expected number of background events to searches rely on passing the stable final-state particles of simulated hadron collisions generated using a so-called event generator code, through a simulation of the experimental detector system. The development of event generators which are capable of reliably predicting the properties of jets produced in association with a core process, e.g. the production of a vector boson, has been the subject of a large amount of research activity during the last ten years. These efforts have led to the appearance of the CKKW and MLM algorithms which are implemented in several event generators, among them SHERPA and ALPGEN + PYTHIA. The large data sample collected by the D0 experiment during Run II offers an excellent opportunity for validating these new event generators against experimental measurements of V + jet production. As argued above, the Z/{gamma}*({yields} e{sup +}e{sup -}) + jets process offers the combination of a clean experimental signature and large production rates, making it the process of choice for these studies.
Nilsen, Henrik Wold; /Freiburg U.
Weak and strong regimes of incompressible magnetohydrodynamic turbulence
Science Conference Proceedings (OSTI)
It is shown that in the framework of the weak turbulence theory, the autocorrelation and cascade time scales are always of the same order of magnitude. This means that, contrary to the general belief, any model of turbulence that implies a large number of collisions among wave packets for an efficient energy cascade (such as the Iroshnikov-Kraichnan model) is not compatible with the weak turbulence theory.
Gogoberidze, G. [Centre for Plasma Astrophysics, K. U. Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Georgian National Astrophysical Observatory, 2a Kazbegi Ave., 0160 Tbilisi, Georgia (United States); Mahajan, S. M. [Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States); Poedts, S. [Centre for Plasma Astrophysics, K. U. Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium)
Measurement and theory of turbulence in RR Lyrae
CORAVEL observations of time-dependent turbulence in RR Lyrae are presented. Variation in the width of the mean velocity correlation function implies turbulent velocities that peak at 10 to 15 km/sec for a brief interval of phase near minimum radius. Comparison with a nonlinear pulsation model shows that these amplitudes of the turbulent velocity are expected near the hydrogen ionization zone, again only near minimum radius.
Benz, W.; Stellingwerf, R.F.
Spatial redistribution of turbulent and mean kinetic energy
Science Conference Proceedings (OSTI)
The turbulent spatial redistribution of turbulent and mean kinetic energy and its exchange is investigated in the framework of an K-{epsilon} model in a magnetized plasma column. The kinetic energy is transferred from the turbulence into the zonal flow around the shear layer. The Reynolds stress profile adjusts to the shear layer, which results in a transport of mean kinetic energy from the region around the shear layer into the shear layer.
Manz, P.; Xu, M.; Fedorczak, N.; Thakur, S. C.; Tynan, G. R. [Center for Momentum Transport and Flow Organization,University of California at San Diego, San Diego, California 92093 (United States); Center for Energy Research, University of California at San Diego, San Diego, California 92093 (United States)
Collisionless inter-species energy transfer and turbulent heating in drift wave turbulence
Science Conference Proceedings (OSTI)
We reconsider the classic problems of calculating 'turbulent heating' and collisionless inter-species transfer of energy in drift wave turbulence. These issues are of interest for low collisionality, electron heated plasmas, such as ITER, where collisionless energy transfer from electrons to ions is likely to be significant. From the wave Poynting theorem at steady state, a volume integral over an annulus r{sub 1}heating as {integral}{sub r{sub 1}} {sup r{sub 2}} dr=-S{sub r}|{sub r{sub 1}{sup r{sub 2}}}{ne}0. Here S{sub r} is the wave energy density flux in the radial direction. Thus, a wave energy flux differential across an annular region indeed gives rise to a net heating, in contrast to previous predictions. This heating is related to the Reynolds work by the zonal flow, since S{sub r} is directly linked to the zonal flow drive. In addition to net heating, there is inter-species heat transfer. For collisionless electron drift waves, the total turbulent energy source for collisionless heat transfer is due to quasilinear electron cooling. Subsequent quasilinear ion heating occurs through linear ion Landau damping. In addition, perpendicular heating via ion polarization currents contributes to ion heating. Since at steady state, Reynolds work of the turbulence on the zonal flow must balance zonal flow frictional damping ({approx}{nu}{sub ii}{sup 2}{approx}|(e{phi}(tilde sign)/T)|{sup 4}), it is no surprise that zonal flow friction appears as an important channel for ion heating. This process of energy transfer via zonal flow has not previously been accounted for in analyses of energy transfer. As an application, we compare the rate of turbulent energy transfer in a low collisionality plasma with the rate of the energy transfer by collisions. The result shows that the collisionless turbulent energy transfer is a significant energy coupling process for ITER plasma.
Zhao, L. [Center for Astrophysics and Space Sciences and Department of Physics, University of California at San Diego, La Jolla, California 92093-0424 (United States); Diamond, P. H. [Center for Astrophysics and Space Sciences and Department of Physics, University of California at San Diego, La Jolla, California 92093-0424 (United States); WCI Center for Fusion Theory, National Fusion Research Institute, Gwahangno113, Yuseong-gu, Daejeon 305-333 (Korea, Republic of)
Internal Wave Interactions with Equatorial Deep Jets. Part II: Acceleration of the Jets
Science Conference Proceedings (OSTI)
What drives the equatorial deep jets is a puzzle because of their isolation from surface forcing by the intervening main pycnocline and the Equatorial Undercurrent, and from lateral boundaries by distances of tens of thousands of kilometers. It ...
Joanna E. Muench; Eric Kunze
The JET2000 Project: Aircraft Observations of the African Easterly Jet and African Easterly Waves
Science Conference Proceedings (OSTI)
Scientific background and motivation for the JET2000 aircraft observing campaign that took place in West Africa during the last week of August 2000 are presented. The Met Research Flight C130 aircraft made two flights along the African easterly ...
C. D. Thorncroft; D. J. Parker; R. R. Burton; M. Diop; J. H. Ayers; H. Barjat; S. Devereau; A. Diongue; R. Dumelow; D. R. Kindred; N. M. Price; M. Saloum; C. M. Tayor; A. M. Tompkins
Gravitational radiation from primordial helical inverse cascade magnetohydrodynamic turbulence
We consider the generation of gravitational waves by primordial helical inverse-cascade magnetohydrodynamic (MHD) turbulence produced by bubble collisions at the electroweak phase transition. We extend the previous study 1 by considering both currently discussed models of MHD turbulence. For popular electroweak phase transition parameter values, the generated gravitational wave spectrum is only weakly dependent on the MHD turbulence model. Compared with the unmagnetized electroweak phase transition case, the spectrum of MHD-turbulence-generated gravitational waves peaks at lower frequency with larger amplitude and can be detected by the proposed Laser Interferometer Space Antenna.
Kahniashvili, Tina [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States); Department of Physics, Laurentian University, Ramsey Lake Road, Sudbury, ON P3E 2C6 (Canada); National Astrophysical Observatory, Ilia Chavchavadze State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Campanelli, Leonardo [Dipartimento di Fisica, Universita di Bari, I-70126 Bari (Italy); INFN - Sezione di Bari, I-70126 Bari (Italy); Gogoberidze, Grigol [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States); National Astrophysical Observatory, Ilia Chavchavadze State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Centre for Plasma Astrophysics, K.U. Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Maravin, Yurii; Ratra, Bharat [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States)
Flashback, Blow out, Emissions and Turbulent Displacement Flame...
NLE Websites -- All DOE Office Websites (Extended Search)
driving physics relating turbulent flame speeds to flashback at conditions relevant to gas turbine engines. Testing was conducted in an optically accessible single nozzle...
Vertical stratified turbulent transport mechanism indicated by remote sensing
Satellite and shipboard data reveal the intermittent vertical information transport mechanism of turbulence and internal waves that mixes the ocean, atmosphere, planets and stars.
Gibson, Carl H; Bondur, Valery G
Vertical stratified turbulent transport mechanism indicated by remote sensing
Satellite and shipboard data reveal the intermittent vertical information transport mechanism of turbulence and internal waves that mixes the ocean, atmosphere, planets and stars.
Carl H. Gibson; R. Norris Keeler; Valery G. Bondur
First Mira Runs Break New Ground with Turbulence Simulations...
NLE Websites -- All DOE Office Websites (Extended Search)
First Mira Runs Break New Ground with Turbulence Simulations July 16, 2013 Printer-friendly version Shortly after Mira, the ALCF's new 10-petaflops supercomputer, entered...
Generalized similarity in finite range solar wind magnetohydrodynamic turbulence
Extended or generalized similarity is a ubiquitous but not well understood feature of turbulence that is realized over a finite range of scales. ULYSSES spacecraft solar polar passes at solar minimum provide \\textit{in situ} observations of evolving anisotropic magnetohydrodynamic turbulence in the solar wind under ideal conditions of fast quiet flow. We find a single generalized scaling function characterises this finite range turbulence and is insensitive to plasma conditions. The recent unusually inactive solar minimum -with turbulent fluctuations down by a factor of $\\sim 2$ in power- provides a test of this invariance.
Chapman, S C
Gyrokinetic simulations of turbulent transport in fusion plasmas
Science Conference Proceedings (OSTI)
This is the final report for a DOE award that was targeted at understanding and simulating turbulence and transport in plasma fusion devices such as tokamaks.
Rogers, Barrett Neil [Dartmouth] [Dartmouth
Turbulence-Flame Interactions in Type Ia Supernovae
Turbulence-Flame Interactions in Type Ia Supernovae A. J.Normalised time (e) Normalised flame speed Normalised time (length scale (cm) Laminar flame width Gibson scale Cell
Aspden, Andrew J; Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50A-1148, Berkeley, CA 94720 (Authors 1, 2 & 3); Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (Author 4); Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (Author 5)
High Frequency Acoustic Wave Scattering From Turbulent Premixed Flames .
??This thesis describes an experimental investigation of high frequency acoustic wave scattering from turbulent premixed flames. The objective of this work was to characterize the� (more)
Narra, Venkateswarlu
Analysis of the Wave Scattering From Turbulent Premixed Flame .
??A theoretical investigation of acoustic wave interactions with turbulent premixed flames was performed. Such interactions affect the characteristic unsteadiness of combustion processes, e.g., combustion instabilities.� (more)
Cho, Ju Hyeong
Experimental study on turbulent natural convection heat transfer in ...
Science Conference Proceedings (OSTI)
Feb 16, 2010 ... ments are conducted to investigate flow and heat transfer ... turbulent region, the heat transfer deterioration occurs for a bubble flow rate Q = 33�...
Experimental study of premixed flames in intense isotropic turbulence
A methodology for investigating premixed turbulent flames propagating in intense isotropic turbulence has been developed. The burner uses a turbulence generator developed by Videto and Santavicca and the flame is stabilized by weak-swirl generated by air injectors. This set-up produces stable premixed turbulent flames under a wide range of mixture conditions and turbulence intensities. The experiments are designed to investigate systematically the changes in flame structures for conditions which can be classified as wrinkled laminar flames, corrugated flames and flames with distributed reaction zones. Laser Doppler anemometry and Rayleigh scattering techniques are used to determine the turbulence and scalar statistics. In the intense turbulence, the flames are found to produce very little changes in the mean and rams velocities. Their flame speed increase linearly with turbulence intensity as for wrinkled laminar flames. The Rayleigh scattering pdfs for flames within the distributed reaction zone regime are distinctly bimodal. The probabilities of the reacting states (i.e. contributions from within the reaction zone) is not higher than those of wrinkled laminar flame. These results show that there is no drastic changes in flame structures at Karlovitz number close to unity. This suggest that the Klimov-Williams criterion under-predicts the resilience of wrinkled flamelets to intense turbulence.
Bedat, B.; Cheng, R.K.
Numerical Simulation of Electro-magnetic Turbulent Inhibitor ...
Science Conference Proceedings (OSTI)
Numerical Modeling of Centrifugally Cast HSS Rolls � Numerical Simulation of Electro-magnetic Turbulent Inhibitor Technology in a Tundish � Optimizing the�...
On the Mellor�Yamada Turbulence Closure Scheme: The Surface Boundary Condition for q2
Science Conference Proceedings (OSTI)
A numerical model that uses a level-2� turbulence closure scheme is used to compare two boundary conditions for the turbulent energy at the air�sea interface. One boundary condition, the most commonly used, sets the turbulent kinetic energy ...
Michael W. Stacey; Stephen Pond
Science Conference Proceedings (OSTI)
We propose a method to identify b-quark jets at trigger level which exploits recently increased CDF trigger system capabilities. b-quark jets identification is of central interest for the CDF high-P{sub T} physics program, and the possibility to select online b-jets enriched samples can extend the physics reaches especially for light Higgs boson searches where the H {yields} b{bar b} decay mode is dominant. Exploiting new trigger primitives provided by two recent trigger upgrades, the Level2 XFT stereo tracking and the improved Level2 cluster-finder, in conjunction with the existing Silicon Vertex Tracker (SVT), we design an online trigger algorithm aimed at selecting good purity b-jets samples useful for many physics measurements, the most important being inclusive H {yields} b{bar b} searches. We discuss the performances of the proposed b-tagging algorithm which must guarantee reasonable trigger rates at luminosity greater than 2 x 10{sup 32} cm{sup -2}s{sup -1} and provide high efficiency on H {yields} b{bar b} events.
Casarsa, M.; /Fermilab; Ristori, L.; /INFN, Pisa; Amerio, S.; Lucchesi, D.; Pagan Griso, S.; /INFN, Padua; Torre, S.T.; /Frascati; Cortiana, G.; /Padua U., Astron. Dept.
Science Conference Proceedings (OSTI)
We consider the interaction between radiation, matter, and a magnetic field in a compact, relativistic jet. The entrained matter accelerates outward as the jet breaks out of a star or other confining medium. In some circumstances, such as gamma-ray bursts (GRBs), the magnetization of the jet is greatly reduced by an advected radiation field while the jet is optically thick to scattering. Where magnetic flux surfaces diverge rapidly, a strong outward Lorentz force develops and radiation and matter begin to decouple. The increase in magnetization is coupled to a rapid growth in Lorentz factor. We take two approaches to this problem. The first examines the flow outside the fast magnetosonic critical surface, and calculates the flow speed and the angular distribution of the radiation field over a range of scattering depths. The second considers the flow structure on both sides of the critical surface in the optically thin regime, using a relaxation method. In both approaches, we find how the terminal Lorentz factor and radial profile of the outflow depend on the radiation intensity and optical depth at breakout. The effect of bulk Compton scattering on the radiation spectrum is calculated by a Monte Carlo method, while neglecting the effects of internal dissipation. The peak of the scattered spectrum sits near the seed peak if radiation pressure dominates the acceleration, but is pushed to a higher frequency if the Lorentz force dominates. The unscattered seed radiation can form a distinct, low-frequency component of the spectrum, especially if the magnetic Poynting flux dominates.
Russo, Matthew [Department of Physics, University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7 (Canada); Thompson, Christopher [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)
Gluon Polarization and Jet Production at STAR
Science Conference Proceedings (OSTI)
I will discuss the most recent measurements of the inclusive jet longitudinal spin asymmetry A LL in polarized proton?proton collisions. STAR collected its largest data sample thus far 4.7? pb ?1 of integrated luminosity at an average beam polarization of ?57%
Pibero Djawotho; the STAR Collaboration
Adaptive LES Methodology for Turbulent Flow Simulations
Science Conference Proceedings (OSTI)
Although turbulent flows are common in the world around us, a solution to the fundamental equations that govern turbulence still eludes the scientific community. Turbulence has often been called one of the last unsolved problem in classical physics, yet it is clear that the need to accurately predict the effect of turbulent flows impacts virtually every field of science and engineering. As an example, a critical step in making modern computational tools useful in designing aircraft is to be able to accurately predict the lift, drag, and other aerodynamic characteristics in numerical simulations in a reasonable amount of time. Simulations that take months to years to complete are much less useful to the design cycle. Much work has been done toward this goal (Lee-Rausch et al. 2003, Jameson 2003) and as cost effective accurate tools for simulating turbulent flows evolve, we will all benefit from new scientific and engineering breakthroughs. The problem of simulating high Reynolds number (Re) turbulent flows of engineering and scientific interest would have been solved with the advent of Direct Numerical Simulation (DNS) techniques if unlimited computing power, memory, and time could be applied to each particular problem. Yet, given the current and near future computational resources that exist and a reasonable limit on the amount of time an engineer or scientist can wait for a result, the DNS technique will not be useful for more than 'unit' problems for the foreseeable future (Moin & Kim 1997, Jimenez & Moin 1991). The high computational cost for the DNS of three dimensional turbulent flows results from the fact that they have eddies of significant energy in a range of scales from the characteristic length scale of the flow all the way down to the Kolmogorov length scale. The actual cost of doing a three dimensional DNS scales as Re{sup 9/4} due to the large disparity in scales that need to be fully resolved. State-of-the-art DNS calculations of isotropic turbulence have recently been completed at the Japanese Earth Simulator (Yokokawa et al. 2002, Kaneda et al. 2003) using a resolution of 40963 (approximately 10{sup 11}) grid points with a Taylor-scale Reynolds number of 1217 (Re {approx} 10{sup 6}). Impressive as these calculations are, performed on one of the world's fastest super computers, more brute computational power would be needed to simulate the flow over the fuselage of a commercial aircraft at cruising speed. Such a calculation would require on the order of 10{sup 16} grid points and would have a Reynolds number in the range of 108. Such a calculation would take several thousand years to simulate one minute of flight time on today's fastest super computers (Moin & Kim 1997). Even using state-of-the-art zonal approaches, which allow DNS calculations that resolve the necessary range of scales within predefined 'zones' in the flow domain, this calculation would take far too long for the result to be of engineering interest when it is finally obtained. Since computing power, memory, and time are all scarce resources, the problem of simulating turbulent flows has become one of how to abstract or simplify the complexity of the physics represented in the full Navier-Stokes (NS) equations in such a way that the 'important' physics of the problem is captured at a lower cost. To do this, a portion of the modes of the turbulent flow field needs to be approximated by a low order model that is cheaper than the full NS calculation. This model can then be used along with a numerical simulation of the 'important' modes of the problem that cannot be well represented by the model. The decision of what part of the physics to model and what kind of model to use has to be based on what physical properties are considered 'important' for the problem. It should be noted that 'nothing is free', so any use of a low order model will by definition lose some information about the original flow.
Oleg V. Vasilyev
Magnetized and collimated millimeter scale plasma jets with astrophysical relevance
Science Conference Proceedings (OSTI)
Magnetized collimated plasma jets are created in the laboratory to extend our understanding of plasma jet acceleration and collimation mechanisms with particular connection to astrophysical jets. In this study, plasma collimated jets are formed from supersonic unmagnetized flows, mimicking a stellar wind, subject to currents and magnetohydrodynamic forces. It is found that an external poloidal magnetic field, like the ones found anchored to accretion disks, is essential to stabilize the jets against current-driven instabilities. The maximum jet length before instabilities develop is proportional to the field strength and the length threshold agrees well with Kruskal-Shafranov theory. The plasma evolution is modeled qualitatively using MHD theory of current-carrying flux tubes showing that jet acceleration and collimation arise as a result of electromagnetic forces.
Brady, Parrish C.; Quevedo, Hernan J. [Texas Center for High Intensity Laser Science, University of Texas at Austin, Austin, Texas 78712 (United States); Valanju, Prashant M. [Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712-1060 (United States); Bengtson, Roger D.; Ditmire, Todd [Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)
The Statistics of Supersonic Isothermal Turbulence
We present results of large-scale three-dimensional simulations of supersonic Euler turbulence with the piecewise parabolic method and multiple grid resolutions up to 2048^3 points. Our numerical experiments describe non-magnetized driven turbulent flows with an isothermal equation of state and an rms Mach number of 6. We discuss numerical resolution issues and demonstrate convergence, in a statistical sense, of the inertial range dynamics in simulations on grids larger than 512^3 points. The simulations allowed us to measure the absolute velocity scaling exponents for the first time. The inertial range velocity scaling in this strongly compressible regime deviates substantially from the incompressible Kolmogorov laws. The slope of the velocity power spectrum, for instance, is -1.95 compared to -5/3 in the incompressible case. The exponent of the third-order velocity structure function is 1.28, while in incompressible turbulence it is known to be unity. We propose a natural extension of Kolmogorov's phenomenology that takes into account compressibility by mixing the velocity and density statistics and preserves the Kolmogorov scaling of the power spectrum and structure functions of the density-weighted velocity v=\\rho^{1/3}u. The low-order statistics of v appear to be invariant with respect to changes in the Mach number. For instance, at Mach 6 the slope of the power spectrum of v is -1.69, and the exponent of the third-order structure function of v is unity. We also directly measure the mass dimension of the "fractal" density distribution in the inertial subrange, D_m = 2.4, which is similar to the observed fractal dimension of molecular clouds and agrees well with the cascade phenomenology.
Alexei G. Kritsuk; Michael L. Norman; Paolo Padoan; Rick Wagner
Rain initiation time in turbulent warm clouds
We present a mean-field model that describes droplet growth due to condensation and collisions and droplet loss due to fallout. The model allows for an effective numerical simulation. We study how the rain initiation time depends on different parameters. We also present a simple model that allows one to estimate the rain initiation time for turbulent clouds with an inhomogeneous concentration of cloud condensation nuclei. In particular, we show that over-seeding even a part of a cloud by small hygroscopic nuclei one can substantially delay the onset of precipitation.
Falkovich, G; Vucelja, M
Rain initiation time in turbulent warm clouds
We present a mean-field model that describes droplet growth due to condensation and collisions and droplet loss due to fallout. The model allows for an effective numerical simulation. We study how the rain initiation time depends on different parameters. We also present a simple model that allows one to estimate the rain initiation time for turbulent clouds with an inhomogeneous concentration of cloud condensation nuclei. In particular, we show that over-seeding even a part of a cloud by small hygroscopic nuclei one can substantially delay the onset of precipitation.
G. Falkovich; M. G. Stepanov; M. Vucelja
Energy flux limitation by tame turbulence
A quasi-linear theory of energy flux limitation by ion acoustic turbulence is presented. This distribution function is modelled by a Maxwellian plus an additional piece which carries a heat flux Q. By taking the fourth moment of the Vlasov equation one finds the anomalous thermal conductivity K approximately 3 v/sub e/ delta/sub De/ (e phi/T/sub e/)$sup -2$. Other moments treated self-consistently include anomalous ion heating, electron cooling, current generation and enhanced inverse bremsstrahlung due to the nonthermal ion fluctuations. (auth)
Manheimer, W.M.
Nonperturbative models of intermittency in edge turbulence
A theory of the probability distribution function (PDF) tails of the blob density in plasma edge turbulence is provided. A simplified model of the fast convective radial transport is used. The theoretically predicted PDF tails corroborate earlier measurements of edge transport, further confirming the strongly non-Gaussian feature of edge transport. It is found that increasing the cross-sectional spatial scale length (L{sub x} and L{sub y}) of the blob results in larger transport, whereas increasing the toroidal scale length (L{sub z}) decreases the PDF. The results imply that the PDF decreases for larger blob speed v{sub b}.
Anderson, Johan; Kim, Eun-jin [Department of Applied Mathematics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)
Science Conference Proceedings (OSTI)
A numerical study of strong kinetic-Alfven turbulence at scales smaller than the ion gyroscale is presented, and a phenomenological model is proposed that argues that magnetic and density fluctuations are concentrated mostly in two-dimensional structures, which leads to their Fourier energy spectra E(k ){proportional_to}k {sup -8/3} , where k is the wavevector component normal to the strong background magnetic field. The results may provide an explanation for recent observations of magnetic and density fluctuations in the solar wind at sub-proton scales.
Boldyrev, Stanislav; Perez, Jean Carlos [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)
Assessment of reduced mechanisms using One Dimensional Stochastic Turbulence model
Giampaolo, T. (2009). The gas turbine handbook : principlesnatural gas. J. Eng. Gas Turbines Power, Masri, A. , Dibble,premixed jet flames at gas turbine conditions. The transient
Chien, Li-Chun
Modeling of combustion noise spectrum from turbulent premixed flames
Modeling of combustion noise spectrum from turbulent premixed flames Y. Liu, A. P. Dowling, T. D, Nantes, France 2321 #12;Turbulent combustion processes generate sound radiation due to temporal changes, this temporal correlation and its role in the modeling of combustion noise spectrum are studied by analyzing
Paris-Sud XI, Université de
Similarity Solutions for the Stratified Turbulent Rayleigh Problem
Science Conference Proceedings (OSTI)
The type of stratified flow suggested by the Kantha Phillips and Azad experiment is examined analytically and shown to be a self-similar, turbulent flow which includes the well-documented fiat-plate, turbulent boundary-layer case. Some relevant ...
George Mellor; Paul T. Strub
Identification of Wind Turbine Response to Turbulent Inflow Structures: Preprint
The National Renewable Energy Laboratory conducted an experiment to obtain detailed wind measurements and corresponding wind turbine measurements in order to establish a causal relationship between coherent turbulent structures and wind turbine blade fatigue loads. Data were collected for one entire wind season from October 2000 to May 2001. During this period, the wind turbine operated under atmospheric conditions that support the formation of coherent turbulent structures 31% of the time. Using the equivalent fatigue load parameter as a measure of wind turbine blade fatigue and using statistical measures of the turbulent fluctuations of the wind, general correlation between the turbulence and the wind turbine response is shown. Direct correlation cannot be resolved with 10-minute statistics for several reasons. Multiple turbulent structures can exist within a 10-minute record, and the equivalent fatigue load parameter is essentially a 10-minute statistic that cannot estimate turbine response to individual turbulent structures. Large-magnitude turbulent fluctuations in the form of instantaneous Reynolds stresses do not necessarily correspond directly to large-magnitude blade root moment amplitudes. Thus, additional work must be done to quantify the negative turbine response and to correlate this response to turbulent inflow parameters over time scales less than 10 minutes.
Hand, M. M.; Kelley, N. D.; Balas, M. J.
On the Turbulent Mixing Length in the Oceanic Boundary Layer
Science Conference Proceedings (OSTI)
Turbulence measurements from under drifting pack ice illustrate the distribution of turbulent mixing length in the well-mixed layer of the upper ocean. Mixing length (? ? K/u*, where K and u* are the local eddy viscosity and square root of ...
Miles G. Mcphee
High-Performance Computing and Visualization of Unsteady Turbulent Flows
Science Conference Proceedings (OSTI)
The history of high-performance computing in turbulent flows is reviewed and their recent topics in industrial use are addressed. Special attention is paid to the validity of the method in flow visualization, and three-dimensional unsteady simulation ... Keywords: CAE, DNS, HPC, LES, turbulence
T. Kobayashi; M. Tsubokura; N. Oshima
Light reradiation in a parametrically turbulent laser plasma
The intensity and spectrum of the light reradiated in a laser plasma are estimated from the theory of parametric turbulence. The possibility of determining the turbulence characteristics from the reradiation spectrum is discussed. It is suggested that the diffuse reflection observed experimentally is related to reradiation.
Krupnova, L.V.; Silin, V.P.; Tikhonchuk, V.T.
Turbulent convection models (TCMs) are thought to be good tools to deal with the convective overshooting in the stellar interior. However, they are too complex to be applied to calculations of stellar structure and evolution. In order to understand the physical processes of the convective overshooting and to simplify the application of TCMs, a semi-analytic solution is necessary. We obtain the approximate solution and asymptotic solution of the TCM in the overshooting region, and find some important properties of the convective overshooting. (1) The overshooting region can be partitioned into three parts: a thin region just outside the convective boundary with high efficiency of turbulent heat transfer, a power-law dissipation region of turbulent kinetic energy in the middle, and a thermal dissipation area with rapidly decreasing turbulent kinetic energy. The decaying indices of the turbulent correlations k, u{sub r}'T'-bar, and T'T'-bar are only determined by the parameters of the TCM, and there is an equilibrium value of the anisotropic degree {omega}. (2) The overshooting length of the turbulent heat flux u{sub r}'T'-bar is about 1H{sub k} (H{sub k} = |dr/dln k|). (3) The value of the turbulent kinetic energy at the convective boundary k{sub C} can be estimated by a method called the maximum of diffusion. Turbulent correlations in the overshooting region can be estimated by using k{sub C} and exponentially decreasing functions with the decaying indices.
Zhang, Q. S.; Li, Y., E-mail: email@example.com, E-mail: email@example.com [National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming 650011 (China)
Verification of clear-air turbulence forecasts June 2002, KNMI
to increase potential energy. Under these conditions turbulence will increase in intensity until different weather conditions. It often occurs in relatively clear skies and is then referred to as clear-airVerification of clear-air turbulence forecasts A. Overeem June 2002, KNMI Technisch rapport #12
Stoffelen, Ad
Effects of Magnetic Field on the Turbulent Wake of a Cylinder in MHD Channel Flow
Results from a free-surface MHD flow experiment are presented detailing the modi cation of vortices in the wake of a circular cylinder with its axis parallel to the applied magnetic fi eld. Experiments were performed with a Reynolds number near Re ~ 104 as the interaction parameter, N = |j x#2; B| / |? (? ? ?), was increased through unity. By concurrently sampling the downstream fluid velocity at sixteen cross-stream locations in the wake, it was possible to extract an ensemble of azimuthal velocity profi les as a function of radius for vortices shed by the cylinder at varying strengths of magnetic field. Results indicate a signi cant change in vortex radius and rotation as N is increased. The lack of deviations from the vortex velocity pro file at high magnetic fi elds suggests the absence of small-scale turbulent features. By sampling the wake at three locations downstream in subsequent experiments, the decay of the vortices was examined and the effective viscosity was found to decrease as N-049�0.4. This reduction in effective viscosity is due to the modi cation of the small-scale eddies by the magnetic fi eld. The slope of the energy spectrum was observed to change from a k-1.8 power-law at low N to a k-3.5 power-law for N > 1. Together, these results suggest the flow smoothly transitioned to a quasi-two-dimensional state in the range 0 < N < 1.
John Rhoads, Eric Edlund and Hantao Ji
Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators
Science Conference Proceedings (OSTI)
The longitudinal beam dynamics in circular accelerators is mainly defined by the interaction of the beam current with the accelerating Radio Frequency (RF) stations. For stable operation, Low Level RF (LLRF) feedback systems are employed to reduce coherent instabilities and regulate the accelerating voltage. The LLRF system design has implications for the dynamics and stability of the closed-loop RF systems as well as for the particle beam, and is very sensitive to the operating range of accelerator currents and energies. Stability of the RF loop and the beam are necessary conditions for reliable machine operation. This dissertation describes theoretical formalisms and models that determine the longitudinal beam dynamics based on the LLRF implementation, time domain simulations that capture the dynamic behavior of the RF station-beam interaction, and measurements from the Positron-Electron Project (PEP-II) and the Large Hadron Collider (LHC) that validate the models and simulations. These models and simulations are structured to capture the technical characteristics of the system (noise contributions, non-linear elements, and more). As such, they provide useful results and insight for the development and design of future LLRF feedback systems. They also provide the opportunity to study diverse longitudinal beam dynamics effects such as coupled-bunch impedance driven instabilities and single bunch longitudinal emittance growth. Coupled-bunch instabilities and RF station power were the performance limiting effects for PEP-II. The sensitivity of the instabilities to individual LLRF parameters, the effectiveness of alternative operational algorithms, and the possible tradeoffs between RF loop and beam stability were studied. New algorithms were implemented, with significant performance improvement leading to a world record current during the last PEP-II run of 3212 mA for the Low Energy Ring. Longitudinal beam emittance growth due to RF noise is a major concern for LHC. Simulations studies and measurements were conducted that clearly show the correlation between RF noise and longitudinal bunch emittance, identify the major LLRF noise contributions, and determine the RF component dominating this effect. With these results, LHC upgrades and alternative algorithms are evaluated to reduce longitudinal emittance growth during operations. The applications of this work are described with regard to future machines and analysis of new technical implementations, as well as to possible future work which would continue the directions of this dissertation.
Mastoridis, Themistoklis; /Stanford U., Elect. Eng. Dept. /SLAC
Visualizing Magneto-Rotational Instability and Turbulent Angular Momentum
NLE Websites -- All DOE Office Websites (Extended Search)
Turbulent Angular Momentum Transport Turbulent Angular Momentum Transport Magneto-Rotational Instability and Turbulent Angular Momentum Transport hydroentropyvisit0400.s.x2005.png In space, gases and other matter often form swirling disks around attracting central objects such as newly formed stars. The presence of magnetic fields can cause the disks to become unstable and develop turbulence, causing the disk material to fall onto the central object. This project will carry out large-scale simulations to test theories on how turbulence can develop in such a scenario. These simulations may provide insights into magnetically caused instabilities being studied on a smaller scale in laboratory experiments. In this image volume rendering has been used to visualize the time evolution of hydrodynamic entropy. The color
Lagrangian Frequency Spectrum as a Diagnostic for Magnetohydrodynamic Turbulence Dynamics
For the phenomenological description of magnetohydrodynamic turbulence competing models exist, e.g., Boldyrev [Phys. Rev. Lett. 96, 115002 (2006)] and Gogoberidze [Phys. Plasmas 14, 022304 (2007)], which predict the same Eulerian inertial-range scaling of the turbulent energy spectrum although they employ fundamentally different basic interaction mechanisms. A relation is found that links the Lagrangian frequency spectrum with the autocorrelation time scale of the turbulent fluctuations {tau}{sub ac} and the associated cascade time scale {tau}{sub cas}. Thus, the Lagrangian energy spectrum can serve to identify weak ({tau}{sub ac}<<{tau}{sub cas}) and strong ({tau}{sub ac{approx}{tau}cas}) interaction mechanisms providing insight into the turbulent energy cascade. The new approach is illustrated by results from direct numerical simulations of two- and three-dimensional incompressible MHD turbulence.
Busse, Angela; Mueller, Wolf-Christian; Gogoberidze, Grigol [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstrasse 2, 85748 Garching (Germany); Georgian National Astrophysical Observatory, 2a Kazbegi Avenue, 0160 Tbilisi (Georgia) and Centre for Plasma Astrophysics, University of Leuven, B-3001 Leuven (Belgium)
Scaling Relations for Turbulence in Multiphase Interstellar Medium
We simulate the dynamics of phase transition in radiatively cooling interstellar gas in three dimensions with a high order hydrodynamic method. We have previously shown (Kritsuk & Norman 2002a) in simulations with non-equilibrium initial conditions that thermal instability induces supersonic turbulence as a by-product of the phase transition which leads to formation of multiphase medium. We rely on a generalization of the She & Leveque (1994) model to study velocity scaling relations in this decaying turbulence and compare those with analogous results for compressible isothermal turbulence. Since radiative cooling promotes nonlinear instabilities in highly supersonic flows, turbulence in our simulations tends to be more intermittent than in the isothermal case. Hausdorff dimension of the most singular dissipative structures, D, can be as high as 2.3, while in supersonic isothermal turbulence D is limited by a more primitive nature of dissipation (shocks): D<=2. We also show that single-phase veloci...
Kritsuk, A G; Kritsuk, Alexei G.; Norman, Michael L.
Enhancement and suppression of heat transfer by MHD turbulence
We study of the effect of turbulence on heat transfer within magnetized plasmas for energy injection velocities both larger and smaller that the Alfven speed. We find that in the latter regime the heat transfer is partially suppressed, while in the former regime the effects of turbulence depend on the intensity of driving. In fact, the scale l at which the turbulent velocity is equal the Alfven velocity is a new important parameter. When the electron mean free path is larger than l, the stronger the the turbulence, the lower thermal conductivity by electrons is. The turbulent motions, however, induces their own advective heat transport, which, for the parameters of intracluster medium (ICM) provides effective heat diffusivity that exceeds the classical Spitzer value.
A. Lazarian
Science Conference Proceedings (OSTI)
Using test-particle simulations, the off-diagonal elements of the diffusion tensor are evaluated numerically. The comparison of the so-obtained time-dependent drift coefficients with analytical approximations shows that, for weak turbulence strengths or for slab turbulence geometry, the weak scattering result provides an excellent agreement with the numerical results. For two- or three-dimensional turbulence geometry, however, neither the classical scattering result nor alternative analytical approaches provide an accurate description of the numerically obtained values. Furthermore, the influence is discussed of a non-constant energy range in the turbulence spectrum and of non-static turbulence, for which the time dependence is modeled using magnetohydrodynamic plasma waves.
Tautz, R. C. [Zentrum fuer Astronomie und Astrophysik, Technische Universitaet Berlin, Hardenbergstrasse 36, D-10623 Berlin (Germany); Shalchi, A., E-mail: email@example.com, E-mail: email@example.com [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada)
Gyrokinetic turbulence: a nonlinear route to dissipation through phase space
This paper describes a conceptual framework for understanding kinetic plasma turbulence as a generalized form of energy cascade in phase space. It is emphasized that conversion of turbulent energy into thermodynamic heat is only achievable in the presence of some (however small) degree of collisionality. The smallness of the collision rate is compensated by the emergence of small-scale structure in the velocity space. For gyrokinetic turbulence, a nonlinear perpendicular phase mixing mechanism is identified and described as a turbulent cascade of entropy fluctuations simultaneously occurring at spatial scales smaller than the ion gyroscale and in velocity space. Scaling relations for the resulting fluctuation spectra are derived. An estimate for the collisional cutoff is provided. The importance of adequately modeling and resolving collisions in gyrokinetic simulations is biefly discussed, as well as the relevance of these results to understanding the dissipation-range turbulence in the solar wind and the electrostatic microturbulence in fusion plasmas.
A. A. Schekochihin; S. C. Cowley; W. Dorland; G. W. Hammett; G. G. Howes; G. G. Plunk; E. Quataert; T. Tatsuno
Reconnection events in two-dimensional Hall magnetohydrodynamic turbulence
Science Conference Proceedings (OSTI)
The statistical study of magnetic reconnection events in two-dimensional turbulence has been performed by comparing numerical simulations of magnetohydrodynamics (MHD) and Hall magnetohydrodynamics (HMHD). The analysis reveals that the Hall term plays an important role in turbulence, in which magnetic islands simultaneously reconnect in a complex way. In particular, an increase of the Hall parameter, the ratio of ion skin depth to system size, broadens the distribution of reconnection rates relative to the MHD case. Moreover, in HMHD the local geometry of the reconnection region changes, manifesting bifurcated current sheets and quadrupolar magnetic field structures in analogy to laminar studies, leading locally to faster reconnection processes in this case of reconnection embedded in turbulence. This study supports the idea that the global rate of energy dissipation is controlled by the large scale turbulence, but suggests that the distribution of the reconnection rates within the turbulent system is sensitive to the microphysics at the reconnection sites.
Donato, S.; Servidio, S.; Carbone, V. [Dipartimento di Fisica, Universita della Calabria, I-87036 Cosenza (Italy); Dmitruk, P. [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Fisica de Buenos Aires, CONICET, Buenos Aires (Argentina); Shay, M. A.; Matthaeus, W. H. [Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Cassak, P. A. [Department of Physics, West Virginia University, Morgantown, West Virginia 26506 (United States)
Gyrokinetic Simulation of Global Turbulent Transport Properties in Tokamak Experiments
A general geometry gyro-kinetic model for particle simulation of plasma turbulence in tokamak experiments is described. It incorporates the comprehensive influence of noncircular cross section, realistic plasma profiles, plasma rotation, neoclassical (equilibrium) electric fields, and Coulomb collisions. An interesting result of global turbulence development in a shaped tokamak plasma is presented with regard to nonlinear turbulence spreading into the linearly stable region. The mutual interaction between turbulence and zonal flows in collisionless plasmas is studied with a focus on identifying possible nonlinear saturation mechanisms for zonal flows. A bursting temporal behavior with a period longer than the geodesic acoustic oscillation period is observed even in a collisionless system. Our simulation results suggest that the zonal flows can drive turbulence. However, this process is too weak to be an effective zonal flow saturation mechanism.
Wang, W.X.; Lin, Z.; Tang, W.M.; Lee, W.W.; Ethier, S.; Lewandowski, J.L.V.; Rewoldt, G.; Hahm, T.S.; Manickam, J.
Transmission Line Analogy for Relativistic Poynting-Flux Jets
Radio emission, polarization, and Faraday rotation maps of the radio jet of the galaxy 3C 303 have shown that one knot of this jet carries a {\\it galactic}-scale electric current and that it is magnetically dominated. We develop the theory of magnetically dominated or Poynting-flux jets by making an analogy of a Poynting jet with a transmission line or waveguide carrying a net current and having a potential drop across it (from the jet's axis to its radius) and a definite impedance which we derive. Time-dependent but not necessarily small perturbations of a Poynting-flux jet are described by the "telegrapher's equations." These predict the propagation speed of disturbances and the effective wave impedance for forward and backward propagating wave components. A localized disturbance of a Poynting jet gives rise to localized dissipation in the jet which may explain the enhanced synchrotron radiation in the knots of the 3C 303 jet, and also in the apparently stationary knot HST-1 in the jet near the nucleus of t...
Lovelace, R V E
Ignition of hydrogen/air mixing layer in turbulent flows
Autoignition of a scalar hydrogen/air mixing layer in homogeneous turbulence is studied using direct numerical simulation. An initial counterflow of unmixed nitrogen-diluted hydrogen and heated air is perturbed by two-dimensional homogeneous turbulence. The temperature of the heated air stream is chosen to be 1,100 K which is substantially higher than the crossover temperature at which the rates of the chain branching and termination reactions become equal. Three different turbulence intensities are tested in order to assess the effect of the characteristic flow time on the ignition delay. For each condition, a simulation without heat release is also performed. The ignition delay determined with and without heat release is shown to be almost identical up to the point of ignition for all of the turbulence intensities tested, and the predicted ignition delays agree well within a consistent error band. It is also observed that the ignition kernel always occurs where hydrogen is focused, and the peak concentration of HO{sub 2} is aligned well with the scalar dissipation rate. The dependence of the ignition delay on turbulence intensity is found to be nonmonotonic. For weak to moderate turbulence the ignition is facilitated by turbulence via enhanced mixing, while for stronger turbulence, whose timescale is substantially smaller than the ignition delay, the ignition is retarded due to excessive scalar dissipation, and hence diffusive loss, at the ignition location. However, for the wide range of initial turbulence fields studied, the variation in ignition delay due to the corresponding variation in turbulence intensity appears to be quite small.
Im, H.G.; Chen, J.H. [Sandia National Labs., Livermore, CA (United States). Combustion Research Facility; Law, C.K. [Princeton Univ., NJ (United States). Dept. of Mechanical and Aerospace Engineering
Heat release effects on decaying homogeneous compressible turbulence
High Mach-number compressible flows with heat release are inherently more complicated than incompressible flows due to, among other reasons, the activation of the thermal energy mode. Such flow fields can experience significant fluctuations in density, temperature, viscosity, conductivity and specific heat, which affect velocity and pressure fluctuations. Furthermore, the flow field cannot be assumed to be dilatation-free in high Mach numbers and even in low Mach-number flows involving combustion, or in boundary layers on heated walls. The main issue in these high-speed and highly-compressible flows is the effect of thermal gradients and fluctuations on turbulence. The thermal field has various routes through which it affects flow structures of compressible turbulence. First, it has direct influence through pressure, which affects turbulence via pressure-strain correlation. The indirect effects of thermal fields on compressible turbulence are through the changes in flow properties. The high temperature gradients alter the transport coefficient and compressibility of the flow. The objective of this work is to answer the following questions: How do temperature fluctuations change the compressible flow structure and energetics? How does compressibility in the flow affect the non-linear pressure redistribution process? What is the main effect of spatial transport-coefficient variation? We perform direct numerical simulations (DNS) to answer the above questions. The investigations are categorized into four parts: 1) Turbulent energy cascade and kinetic-internal energy interactions under the influence of temperature fluctuations; 2) Return-to-isotropy of anisotropic turbulence under the influence of large temperature fluctuations; 3) The effect of turbulent Mach number and dilatation level on small-scale (velocity-gradient) dynamics; 4) The effect of variable transport-coefficients (viscosity and diffusivity) on cascade and dissipation processes of turbulence. The findings lead to a better understanding of temperature fluctuation effects on non-linear processes in compressible turbulence. This improved understanding is expected to provide direction for improving second-order closure models of compressible turbulence.
Lee, Kurn Chul
Cryogenic target formation using cold gas jets
A method and apparatus using cold gas jets for producing a substantially uniform layer of cryogenic materials on the inner surface of hollow spherical members having one or more layers, such as inertially imploded targets are disclosed. By vaporizing and quickly refreezing cryogenic materials contained within a hollow spherical member, a uniform layer of the materials is formed on an inner surface of the spherical member. Basically the method involves directing cold gas jets onto a spherical member having one or more layers or shells and containing the cryogenic material, such as a deuterium-tritium (DT) mixture, to freeze the contained material, momentarily heating the spherical member so as to vaporize the contained material, and quickly refreezing the thus vaporized material forming a uniform layer of cryogenic material on an inner surface of the spherical member. 4 figs.
Hendricks, C.D.
Numerical Issues of Monte Carlo PDF for Large Eddy Simulations of Turbulent Flames
piloted methane jet flame (Sandia Flame D),� Presented atof a pure mixing jet and Sandia Flame D using a steady-stateon pure mixing jet and Sandia flame D with a steady-
Bisetti, Fabrizio; Chen, J Y
Scrape-off layer tokamak plasma turbulence
Science Conference Proceedings (OSTI)
Two-dimensional (2D) interchange turbulence in the scrape-off layer of tokamak plasmas and their subsequent contribution to anomalous plasma transport has been studied in recent years using electron continuity, current balance, and electron energy equations. In this paper, numerically it is demonstrated that the inclusion of ion energy equation in the simulation changes the nature of plasma turbulence. Finite ion temperature reduces floating potential by about 15% compared with the cold ion temperature approximation and also reduces the radial electric field. Rotation of plasma blobs at an angular velocity about 1.5 Multiplication-Sign 10{sup 5} rad/s has been observed. It is found that blob rotation keeps plasma blob charge separation at an angular position with respect to the vertical direction that gives a generation of radial electric field. Plasma blobs with high electron temperature gradients can align the charge separation almost in the radial direction. Influence of high ion temperature and its gradient has been presented.
Bisai, N.; Singh, R.; Kaw, P. K. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat 382428 (India)
Ejector device for direct injection fuel jet
Disclosed is a device for increasing entrainment and mixing in an air/fuel zone of a direct fuel injection system. The device comprises an ejector nozzle in the form of an inverted funnel whose central axis is aligned along the central axis of a fuel injector jet and whose narrow end is placed just above the jet outlet. It is found that effective ejector performance is achieved when the ejector geometry is adjusted such that it comprises a funnel whose interior surface diverges about 7.degree. to about 9.degree. away from the funnel central axis, wherein the funnel inlet diameter is about 2 to about 3 times the diameter of the injected fuel plume as the fuel plume reaches the ejector inlet, and wherein the funnel length equal to about 1 to about 4 times the ejector inlet diameter. Moreover, the ejector is most effectively disposed at a separation distance away from the fuel jet equal to about 1 to about 2 time the ejector inlet diameter.
Upatnieks, Ansis (Livermore, CA)
High momentum jets and hadrons can be used as probes for the quark gluon plasma (QGP) formed in nuclear collisions at high energies. We investigate the influence of fluctuations in the fireball on jet quenching observables by comparing propagation of light quarks and gluons through averaged, smooth QGP fireballs with event-by-event jet quenching using realistic inhomogeneous fireballs. We find that the transverse momentum and impact parameter dependence of the nuclear modification factor R{sub AA} can be fit well in an event-by-event quenching scenario within experimental errors. However the transport coefficient {cflx q} extracted from fits to the measured nuclear modification factor R{sub AA} in averaged fireballs underestimates the value from event-by-event calculations by up to 50%. On the other hand, after adjusting {cflx q} to fit R{sub AA} in the event-by-event analysis we find residual deviations in the azimuthal asymmetry v{sub 2} and in two-particle correlations, that provide a possible faint signature for a spatial tomography of the fireball. We discuss a correlation function that is a measure for spatial inhomogeneities in a collision and can be constrained from data.
Fries, R.J.; Rodriguez, R.; Ramirez, E.
Composition, collimation, contamination: the jet of Cygnus X-1
We model the observed size and brightness of the VLBA radio core of the jet in Cygnus X-1 to derive an expression for the jet power as a function of basic jet parameters. We apply this expression to recent constraints on the jet power from observations of a large scale shocked shell around the source by Gallo et al. 2005, which leads us to a set of alternative conclusions: either (a) the jet contains large amounts of protons: more than 2000 protons per radio emitting electron, (b) it has a very low radio volume filling factor of f source of the kinetic energy powering the ISM shell, or (d) its asymptotic behavior differs fundamentally from a broad set of plausible analytic jet models.
Sebastian Heinz
A parallel solution - adaptive method for three-dimensional turbulent non-premixed combusting flows
Science Conference Proceedings (OSTI)
A parallel adaptive mesh refinement (AMR) algorithm is proposed and applied to the prediction of steady turbulent non-premixed compressible combusting flows in three space dimensions. The parallel solution-adaptive algorithm solves the system of partial-differential ... Keywords: Adaptive mesh refinement, Parallel solution-adaptive algorithm, Turbulent combustion, Turbulent diffusion flames, Turbulent non-premixed flames
Xinfeng Gao; Clinton P. T. Groth
Study of Flow, Turbulence and Transport on the Large Plasma Device
Axial versus Radial Transport . . . . . . . . . . . . .223 A LAPD Transport172 Turbulence and Transport
Schaffner, David A.
We use frequency-dependent position shifts of flat-spectrum radio cores to estimate the kinetic power of active galactic nucleus (AGN) jets. We find a correlation between the derived jet powers and AGN narrow-line luminosity, consistent with the well-known relation for radio galaxies and steep spectrum quasars. This technique can be applied to intrinsically weak jets even at high redshift.
Shabala, S. S.; Santoso, J. S. [School of Mathematics and Physics, University of Tasmania, Private Bag 37, Hobart, TAS 7001 (Australia); Godfrey, L. E. H. [International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, Western Australia 6845 (Australia)
A computational study of highly viscous impinging jets
Two commercially-available computational fluid dynamics codes, FIDAP (Fluent, Inc., Lebanon, NH) and FLOW-3D (Flow Science, Inc., Los Alamos, NM), were used to simulate the landing region of jets of highly viscous fluids impinging on flat surfaces. The volume-of-fluid method was combined with finite difference and finite element approaches to predict the jet behavior. Several computational models with varying degrees of physical realism were developed, and the results were compared with experimental observations. In experiments, the jet exhibited several complex behaviors. As soon as it exited the nozzle, the jet began to neck down and become narrower. When it impacted the solid surface, the jet developed an instability near the impact point and buckled to the side. This buckling became a spiraling motion, and the jet spiraled about the impact point. As the jet spiraled around, a cone-shaped pile was build up which eventually became unstable and slumped to the side. While all of these behaviors were occurring, air bubbles, or voids, were being entrapped in the fluid pool. The results obtained from the FLOW-3D models more closely matched the behavior of real jets than the results obtained from /the FIDAP models. Most of the FLOW-3D models predicted all of the significant jet behaviors observed in experiments: necking, buckling, spiraling, slumping, and void entrapment. All of the FIDAP models predicted that the jet would buckle relatively far from the point of impact, whereas the experimentally observed jet behavior indicates that the jets buckle much nearer the impact point. Furthermore, it was shown that FIDAP is incapable of incorporating heat transfer effects into the model, making it unsuitable for this work.
Silva, M.W. [Univ. of Texas, Austin, TX (United States). Dept. of Mechanical Engineering
Neutralization of H/sup -/ beams with gas jets
A test facility was constructed to create a compact curtain-shaped gas jet as a first-generation operational neutralizer for the 150 keV H/sup -/ beam. Different gases and vapors were considered, their optimum target thicknesses and neutralization efficiencies with respect to beam energies were explored. Two techniques of gas jet formation were compared. Multiparallel-channel effusive jets of CO/sub 2/ and H/sub 2/ were selected as test candidates.
Lam, C.K.
Nonlinear Flow Generation By Electrostatic Turbulence In Tokamaks
Global gyrokinetic simulations have revealed an important nonlinear flow generation process due to the residual stress produced by electrostatic turbulence of ion temperature gradient (ITG) modes and trapped electron modes (TEM). In collisionless TEM (CTEM) turbulence, nonlinear residual stress generation by both the fluctuation intensity and the intensity gradient in the presence of broken symmetry in the parallel wave number spectrum is identified for the first time. Concerning the origin of the symmetry breaking, turbulence self-generated low frequency zonal flow shear has been identified to be a key, universal mechanism in various turbulence regimes. Simulations reported here also indicate the existence of other mechanisms beyond E � B shear. The ITG turbulence driven �intrinsic� torque associated with residual stress is shown to increase close to linearly with the ion temperature gradient, in qualitative agreement with experimental observations in various devices. In CTEM dominated regimes, a net toroidal rotation is driven in the cocurrent direction by �intrinsic� torque, consistent with the experimental trend of observed intrinsic rotation. The finding of a �flow pinch� in CTEM turbulence may offer an interesting new insight into the underlying dynamics governing the radial penetration of modulated flows in perturbation experiments. Finally, simulations also reveal highly distinct phase space structures between CTEM and ITG turbulence driven momentum, energy and particle fluxes, elucidating the roles of resonant and non-resonant particles.
W.X. Wang, P.H. Diamond, T.S. Hahm, S. Ethier, G. Rewoldt, and W.M. Tang
Nonlinear flow generation by electrostatic turbulence in tokamaks
Global gyrokinetic simulations have revealed an important nonlinear flow generation process due to the residual stress produced by electrostatic turbulence of ion temperature gradient (ITG) modes and trapped electron modes (TEMs). In collisionless TEM (CTEM) turbulence, nonlinear residual stress generation by both the fluctuation intensity and the intensity gradient in the presence of broken symmetry in the parallel wavenumber spectrum is identified for the first time. Concerning the origin of the symmetry breaking, turbulence self-generated low frequency zonal flow shear has been identified to be a key, universal mechanism in various turbulence regimes. Simulations reported here also indicate the existence of other mechanisms beyond ExB shear. The ITG turbulence driven 'intrinsic' torque associated with residual stress is shown to increase close to linearly with the ion temperature gradient, in qualitative agreement with experimental observations in various devices. In CTEM dominated regimes, a net toroidal rotation is driven in the cocurrent direction by intrinsic torque, consistent with the experimental trend of observed intrinsic rotation. The finding of a 'flow pinch' in CTEM turbulence may offer an interesting new insight into the underlying dynamics governing the radial penetration of modulated flows in perturbation experiments. Finally, simulations also reveal highly distinct phase space structures between CTEM and ITG turbulence driven momentum, energy, and particle fluxes, elucidating the roles of resonant and non-resonant particles.
Wang, W. X.; Hahm, T. S.; Ethier, S.; Rewoldt, G.; Tang, W. M. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States); Diamond, P. H. [University of California, San Diego, La Jolla, California 92093 (United States)
The dissipation of turbulence in the weakly collisional solar wind plasma is governed by unknown kinetic mechanisms. Two candidates have been suggested to play an important role in the dissipation, collisionless damping via wave-particle interactions and dissipation in small-scale current sheets. High resolution spacecraft measurements of the turbulent magnetic energy spectrum provide important constraints on the dissipation mechanism. The limitations of popular fluid and hybrid numerical schemes for simulation of the dissipation of solar wind turbulence are discussed, and instead a three-dimensional kinetic approach is recommended. We present a three-dimensional nonlinear gyrokinetic simulation of solar wind turbulence at electron scales that quantitatively reproduces the exponential form of the turbulent magnetic energy spectrum measured in the solar wind. A weakened cascade model that accounts for nonlocal interactions and collisionless Landau damping also quantitatively agrees with the observed exponential form. These results establish that a turbulent cascade of kinetic Alfven waves that is terminated by collisionless Landau damping is sufficient to explain the observed magnetic energy spectrum in the dissipation range of solar wind turbulence.
TenBarge, J. M.; Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Dorland, W., E-mail: firstname.lastname@example.com [Department of Physics, University of Maryland, College Park, MA 20742-3511 (United States)