Title of Invention: Control of aerodynamic forces by variable wetted surface morphology Abstract: Systems and methods for providing dynamic control to a vehicle in a dynamic fluid. The systems and methods of the invention relate to one or more morphable surfaces that can be controlled by a controller and an actuator in an active manner to provide asperities that interact with a fluid moving across the morphable surfaces. By controlling the size, shape and location of the asperities, one can exert control authority over the motion of the vehicle relative to the fluid, including a speed, a direction and an attitude of the vehicle. Examples of materials that provide suitable morphable surfaces include ionic polymer metal composites and shape memory polymers, both of which types of material are commercially available. Useful morphable surface systems have been examined and are described. Detailed Description: Part general_description_paragraphs: Part CROSS-REFERENCE TO RELATED APPLICATIONS: This application is a continuation of U.S. patent application Ser. No. 12/117,959 filed May 9, 2008, now U.S. Pat. No. 8,276,851, which claimed priority to and the benefit of U.S. provisional patent application Ser. No. 60/928,737, filed May 10, 2007, each of which applications is incorporated herein by reference in its entirety. This application is related to co-pending U.S. patent application Ser. No. 12/106,638, filed Apr. 21, 2008, which application is incorporated herein by reference in its entirety. Part STATEMENT REGARDING FEDERALLY FUNDED RESEARCH OR DEVELOPMENT: This invention was made with government support under Grant No. FA9550-08-1-0049 awarded by the Air Force (AFOSR). The government has certain rights in the invention. Part FIELD OF THE INVENTION: The invention relates to aerodynamic applications in general and particularly to control of aerodynamic forces in applications that employ morphing surfaces. Part BACKGROUND OF THE INVENTION: Various methods and systems have been used to attempt to control boundary layer flow in aerodynamic systems. These include passive methods for boundary layer control including static roughness, passive, compliant surfaces, and active methods such as flaps, rudders and ailerons. In particular, several research initiatives have sought to utilize morphing concepts for flow control purposes. The most notable large-scale agency-sponsored efforts include the DARPA Micro Adaptive Flow Control (MAFC) program and micro-aero adaptive control in the NASA Morphing project, both of which have exploited smart structures and advanced discrete MEMs actuator concepts that require low actuation energy to target control of large-scale aerodynamic flows and multi-point adaptability in aircraft operations. There is a rich technical literature that describes laminar flow, turbulent flow, transitions between the two flow regimes, and the interaction of flow regimes with various surface conditions, such as surface roughness. Classical results for turbulent boundary layers, such as Townsend's hypothesis that the outer-scaling layer is not affected by the roughness other than through the friction velocity, and the logarithmic scaling of the mean velocity with the effective roughness amplitude, k, as the scaling lengthscale, hold only when k is small compared to the boundary layer thickness, δ, i.e., k/δ<<1, which is not always satisfied in lower Reynolds number experiments. The latter scaling also only holds when the flow has reached equilibrium. In laminar flows, roughness is known to enhance linear receptivity to external disturbances, leading to increases in the disturbance growth rates and reductions in the critical Reynolds number for transition to turbulence. In practical airfoil flows, under certain conditions in-flight wing icing may lead to the generation of a temporary static roughness distribution, with detrimental, or at least unplanned, implications for the aerodynamic performance of the vehicle. Previous patents in the field of flow control include U.S. Pat. No. 4,516,747, issued May 14, 1985 to Lurz entitled “Method and apparatus for controlling the boundary layer flow over the surface of a body,” U.S. Pat. No. 5,961,080 issued Oct. 5, 1999 to Sinha, entitled “System for efficient control of flow separation using a driven flexible wall,” and an International Application published under the PCT as International Publication No. WO 2006/040532 A1, published Apr. 20, 2006, in the names of Morrison, J. F., Dearing S. S., Arthur, G. G., McKeon, B. J and Cui, Z., entitled “Intelligent Fluid Flow Surfaces.” U.S. Pat. No. 4,516,747 describes a system for boundary layer control by damping of laminar instability or turbulent velocity fluctuations using sensors and vibration transmitters. U.S. Pat. No. 5,961,080 describes a flexible wall that can be used either to drive or sense an external flow by means of sub-surface capacitive transducers. International Publication No. WO 2006/040532 A1 describes distributed “active”, or time-dependent, dimples fabricated from electrostrictive polymer with surface-deposited electrodes. In particular, International Publication No. WO 2006/040532 A1 teaches that the use of dimples is “much more effective than surface roughness.” International Publication No. WO 2006/040532 A1 describes designs and manufacturing methods that are specifically intended to achieve a deflection of a continuous sheet to provide depressions or dimples in the continuous sheet in preference to protrusions. A number of problems in applying previous flow control methods and systems have been observed. One drawback to using passive devices for flow control lies in degraded aerodynamic performance in flow regimes away from those where the control is useful. Some drawbacks in using some active devices can be the complexity of a control system, and the need for expendables such as gases or liquids that are consumed, which add weight, and which limit the duration of operation of the system by virtue of being available in only a finite amount. There is a need for improved aerodynamic control surface systems and methods. Part SUMMARY OF THE INVENTION: In one aspect, the invention relates to a vehicle configured to operate using a morphable skin to manipulate viscous boundary layer processes. The vehicle comprises a vehicle having a surface; a morphable skin having first and second surfaces, the first surface of the morphable skin being attached to at least a portion of the surface of the vehicle, the second surface of the morphable skin configured to exhibit a morphable configuration relative to the surface of the vehicle; an actuator in operative communication with the morphable skin, the actuator configured to apply a control signal to the morphable skin; and a controller in communication with the actuator, the controller configured to provide a command to the actuator to control at least one of a speed, a direction and an attitude, the command based at least in part on a deviation of a perceived speed, direction or attitude from a desired speed, direction or attitude. In response to a command signal provided to the actuator, the actuator controls the second surface of the skin so that the skin assumes a modified surface configuration relative to the surface of the vehicle so as to control an aerodynamic force to exert a control authority over at least one of the speed, the direction and the attitude of the vehicle. In one embodiment, the morphable skin comprises an ionic polymer metal composite. In one embodiment, the vehicle further comprises electrodes in electrical communication with the morphable skin. In one embodiment, the control signal is an electrical signal applied to the electrodes. In one embodiment, the morphable skin comprises a shape memory material. In one embodiment, the controller is an input/output device configured to be operated by a human operator. In one embodiment, the controller is a general purpose programmable computer configured to operate with commands provided by software recorded on a machine-readable medium. In one embodiment, the modified surface configuration relative to the surface of the vehicle comprises a surface asperity of the order of 1 millimeter. In one embodiment, the modified surface configuration relative to the surface of the vehicle comprises a surface asperity having a height of the order of 10 percent or less than a boundary layer thickness of a fluid passing over the apparatus. In one embodiment, the modified surface configuration relative to the surface of the vehicle comprises a surface asperity having a height represented by the relation m*v/uτ, in which v is a fluid kinematic viscosity, uτ is a friction velocity equal to a square root of a ratio of wall shear stress τ to a fluid density ρ, and 0<m≦100. In one embodiment, the modified surface configuration relative to the surface of the vehicle has a response frequency of the order of 1 kiloHertz. In one embodiment, the modified surface configuration relative to the surface of the vehicle has a response frequency of less than the order of the viscous frequency, given by uτ2/v, in which v is a fluid kinematic viscosity, and uτ is a friction velocity equal to a square root of a ratio of wall shear stress τ to a fluid density ρ. In another aspect, the invention features a method of operating a vehicle. The method comprises the steps of: providing a vehicle having a surface; providing a morphable skin having first and second surfaces, the first surface of the morphable skin attached to at least a portion of the surface of the vehicle, the second surface of the morphable skin configured to exhibit a morphable configuration relative to the surface of the vehicle; providing an actuator in operative communication with the morphable skin, the actuator configured to apply a control signal to the morphable skin; providing a controller in communication with the actuator, the controller configured to provide a command to the actuator to control at least one of a speed, a direction and an attitude, the command based at least in part on a deviation of a perceived speed, direction or attitude from a desired speed, direction or attitude; and applying a control signal to the morphable skin from the actuator. In response to the control signal, the second surface of the morphable skin is caused to assume a modified surface configuration relative to the surface of the vehicle to exert a control authority over at least one of the speed, the direction and the attitude of the vehicle. In one embodiment, the morphable skin comprises an ionic polymer metal composite. In one embodiment, the method of operating a vehicle further comprises the step of providing electrodes in electrical communication with the morphable skin. In one embodiment, the control signal is an electrical signal applied to the electrodes. In one embodiment, the morphable skin comprises a shape memory material. In one embodiment, the controller comprises an input/output device configured to be operated by a human operator. In one embodiment, the controller is a general purpose programmable computer configured to operate with commands provided by software recorded on a machine-readable medium. In one embodiment, the modified surface configuration relative to the surface of the vehicle comprises a surface asperity of the order of 1 millimeter. In one embodiment, the modified surface configuration relative to the surface of the vehicle comprises a surface asperity having a height of the order of 10 percent or less than a boundary layer thickness of a fluid passing over the apparatus. In one embodiment, the modified surface configuration relative to the surface of the vehicle comprises a surface asperity having a height represented by the relation m*v/uτ, in which v is a fluid kinematic viscosity, uτ is a friction velocity equal to a square root of a ratio of wall shear stress τ to a fluid density ρ, and 0<m≦100. In one embodiment, the modified surface configuration relative to the surface of the vehicle is attained in a time of the order of 1 millisecond. In one embodiment, the modified surface configuration relative to the surface of the vehicle has a response frequency of less than the order of the viscous frequency, given by uτ2/v, in which v is a fluid kinematic viscosity, and uτ is a friction velocity equal to a square root of a ratio of wall shear stress τ to a fluid density ρ. The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims. Part DETAILED DESCRIPTION OF THE INVENTION: This application describes the use of controlled changes to the global morphology of surfaces below external or internal flows to manipulate viscous boundary layer processes. In describing the invention, reference will be made to a vehicle. It is to be understood that the invention can apply equally to a vehicle moving in a fluid, and to a fluid flowing over one or more surfaces of an object such as a vehicle or to a fluid flowing through a duct. What is of importance is the relative motion of the vehicle and the fluid in which the vehicle is immersed, and it is of little consequence whether the vehicle is moving, the fluid is moving or both are moving, so long as the relative motion of the vehicle and the fluid are the same in whichever frame of reference is applied. As used hereinafter, the term “vehicle” will denote any of an object capable of motion through a fluid, such as a car, a boat, or a plane; an object that is not movable but that can be subjected to forces created by the motion of a fluid around or past the object (such as a building or a bridge subjected to wind loading); and an object such as a duct or an orifice through which fluid can flow and which is subjected to forces (and equally subjects the fluid to forces) as a consequence of the relative motion of the fluid and the object. The viscous boundary layers can be laminar or turbulent. The controlled morphological changes allow one to gain control authority over the magnitude, direction and distribution of aerodynamic forces. The controlled morphological changes can include either or both of global changes in the roughness of a surface that interacts with a fluid, and local geometrical changes of the surface that interacts with a fluid, such as dynamically creating local surface distortions. It is believed that this technology will provide a new method for exerting control authority to replace or augment traditional control surfaces. The boundary layer processes in question include, for example, both enhancement and suppression of steady and unsteady laminar and turbulent flow separation, flow transition, turbulent mixing leading to elevated skin friction with respect to the laminar case and transonic flows. That is, flow conditions that are receptive to small perturbation, either by earlier design of the flow or by identification of appropriate locations in the flow. It is believed that the required morphological changes can be obtained by harnessing mechanical properties including buckling instabilities, phase changes, magnetic and electronic characteristics of materials such as electroactive polymers, thin film-substrate composites and shape memory polymers and alloys. Both step changes, or “on-off roughness”, and time-dependent amplitude disturbances are envisioned, where the frequency of actuation in the latter case depends on the physics of the particular flow to be controlled. It is anticipated that the required maximum deformation parameters in water or air as measured under laboratory conditions will be of the order of 1 mm for the peak roughness amplitude, with peak frequency requirements of the order of 1 kHz, based on conditions for a fully-rough wall operating at the burst frequency of an undisturbed turbulent boundary layer. These magnitudes will likely be smaller for application where the fluid flow is more rapid, such as in flight applications. This bulk boundary condition approach avoids discrete actuator-flow interactions, with the associated difficulty in modeling. The control surface may be flexible and a non-structural or structural part of an aero- or hydro-dynamic vehicle or device. As used herein, the term “aerodynamic” will be understood to refer generally to vehicle or vehicles that operate according to either aerodynamic or hydrodynamic principles, unless a statement so construed is illogical. Drive electronics for materials that require activation may form an integrated part of the surface. Power requirements will be small due to the extremely small actuation amplitudes required. This method of the generation of aerodynamic control belongs to a class with minimum required power because the characteristics of the fluid flow are used to obtain a large amplification of the input disturbance. As such, it is anticipated that the technology can be used in a feedback control loop with a controller that is automated, e.g., one that uses a computer operating with commands provided by software recorded on a machine-readable medium in order to obtain specific control objectives related to optimized vehicle flight or motion, such as controlling at least one of a speed, a direction and an attitude (e.g., one or more of pitch, tilt, and yaw). The computer receives signals from sensors that report information about the perceived speed, direction and attitude of the vehicle, and computes commands calculated to correct the speed, direction and/or attitude to provide a desired speed, direction and attitude. In other situations, the controller can be a human operator, who provides control commands by operating a control input/output device such as one or more of a joystick, a pointing device, a heads-up display, a keyboard, or other conventional input/output device that allows the human operator to perceive at least one of a speed, a direction and an attitude and to issue corrective commands when the perceived speed, direction or attitude differs from a desired speed, direction or attitude. As an example, the control authority that can be obtained from the appropriate use of surface perturbations could be used in order to permit operator-directed control of the flight characteristics of a vehicle, for example attitude, lift or drag. It is envisioned that this method of control could be used either to augment or ultimately replace traditional control surfaces such as ailerons, elevators, rudder, and flaps. Benefits of this technology are expected to include one or more of reduced weight associated with the control device, reduced power requirement, and an altered signature. While these applications may be enumerated here, other similar applications are anticipated. Initial laboratory studies of the control authority that can be generated using a change in the surface roughness boundary condition of an airfoil are described. The present disclosure describes systems and methods to create materials capable of dynamic changes in surface morphology. In one embodiment, the changes in surface morphology specifically comprise systems and methods designed to create asperities in a continuous surface. As used herein, the term “asperity” is meant to denote a slight projection from a surface, such as a point or bump. See The American Heritage® Dictionary of the English Language, Fourth Edition, Houghton Mifflin Company, 2004. In particular, by applying the principles of the invention one can modify the geometry and especially the amplitude of an asperity on a morphable free surface. In one embodiment, by modifying the size, shape and location of such asperities, the hydrodynamic roughness characteristics of the surface when placed in a fluid flow can be tailored to fluid dynamic advantage. In other embodiments, a local geometrical feature of a surface can be dynamically controlled, for example by changing the local geometry so as to provide a local geometrical disturbance such as a single asperity at a selected location and having a selected size and shape. These systems and methods are expected to provide such advantages as the control of laminar and turbulent flow separation, control of flow transition, reduction of turbulent skin friction, and a new method for exerting control authority (e.g., replacing traditional control surfaces). It is expected that these “dynamic surfaces” can be fabricated from ionic polymer metal composite, an electro-active polymer commonly used in artificial muscle applications, when such a material is constrained on one side. In this arrangement, the material would permit the generation of both binary, “on-off” roughness, and time-periodic roughness geometries. Binary roughness is an operational regime in which a surface remains smooth until wall roughness is aerodynamically beneficial, e.g. as a trip to induce transition to turbulence, to increase local skin friction in turbulent flow, or to otherwise improve aerodynamic performance. Time-periodic roughness geometries provide a regime in which one can inject additional length- and time-scales at the wall boundary. It is believed that vorticity flux arising from dynamically rough surfaces with optimized properties and variation parameters can be used to manipulate the near-wall turbulence cycle in turbulent boundary layers with a view to manipulating local shear stress, providing such advantages as enhancement for separation control, reduction for skin friction control and asymmetry for augmentation or replacement of traditional control surfaces. In keeping with the principles of the invention, the surfaces are expected to be tailored to be as rough as possible while maintaining hydrodynamic smoothness in the unactuated state for given flow conditions. Under an applied electric potential, the material comprising the free surface will morph to enhance the local surface amplitude, creating hydrodynamic roughness of time-dependent amplitude. It is anticipated that the required maximum deformation parameters for systems operating in water or air, under conditions found in typical low- to mid-Reynolds number laboratory experiments, will be of the order of 1 mm for the peak roughness amplitude, with peak frequency requirements of the order of 1 kHz, based on conditions for a fully-rough wall operating at the burst frequency of an undisturbed turbulent boundary layer. These magnitudes are expected to be smaller for in flight applications. This bulk boundary condition approach avoids discrete actuator-flow interactions, with the associated difficulty in modeling. It is expected that the systems and methods of the invention will provide the ability to control both static roughness interactions with the flow, which represents the zero frequency limit of a dynamic roughness, and transient and/or time-periodic effects. Based on results that have been obtained and that are described hereinbelow, it is expected that the systems and methods of the invention will provide the ability to generate dynamic roughness on a flexible surface that can form either a non-structural or a structural part of an aero- or hydro-dynamic vehicle or device. In some embodiments, drive electronics form an integrated part of the surface. This approach is possible because of recent advances in active materials. Materials that are believed to be suitable for this application are Ionic Polymer Metal Composites (IPMC), which is one class of an Electro-Active Polymer (EAP). An IPMC can be bought off-the-shelf, for example from Environmental Robots, Inc. (E.R.I.) of 909 Virginia NE, Suite 205, Albuquerque, N. Mex. 87108. Ionic Polymer Metal Composite (IPMC) IPMC is comprised of a sandwich of an ionomeric perfluorinated Polymer Ion Exchange Membrane (PIEM) such as Nafion® 117, available from DuPont, between surface depositions of a conducting, catalytic material such as platinum that also provides metal electrodes embedded or attached on both sides. In a fully-hydrated configuration, the material has a pore and channel morphology that can be tailored to be permeable to cations but impermeable to anions. The Nafion® polymer is comprised of a hydrophobic fluorocarbon backbone, fixed hydrophilic SO3− anions, and mobile hydrophilic H+ cations. This material has been found to be compatible with water, and when immersed in an aqueous solution it will swell until equilibrium is reached. Nafion® membranes are used in PEM fuel cells. FIG. 1 is a diagram that illustrates the basic principle of strain generation in IPMC under an electric field of positive, negligible and negative sign. The schematic also represents the method of dynamic roughness actuation in a constrained configuration. When an electric potential is applied to a material (or to a liquid) in which both anions and cations are free to move, the oppositely charged ions travel in opposite directions resulting in no net momentum. Under an applied electric field E, the resultant electroosmotic pressure gradient −∇p is governed by the following equations: J=σE−L12∇p (1) Q=L21E−K∇p (2) where J is the current density of the ion transport perpendicular to the electrodes, σ is the membrane conductance, L12=L21˜10−1, Q is the water flux and K is the Darcy permeability of the membrane. The migration of both cations and electrophoretic solvent (free water) to the electrode (cathode) induces a large bending stress toward the anode as shown in FIG. 2. FIG. 2 is a diagram that illustrates the IPMC actuation in cantilevered configuration, demonstrating bending towards the anode, for a cation exchange membrane. In an IPMC only the cations are allowed to move since the anion structures are fixed by being attached to the Nafion® polymer backbone. As a result, when a voltage is applied, the hydrophilic cations as well as attracted water molecules migrate towards the cathode (through channels in the hydrophobic backbone structure). This electro-osmotic process results in a concentration of water at the cathode which causes it to expand, while the anode side contracts. A net bending motion towards the anode side is observed. In FIG. 2, a deactivated (unbent) sample of an IPMC is schematically shown on the left, and an activated sample is schematically shown on the right. It has been found that a voltage between 1-3V is sufficient to cause a bending motion in an IPMC. However, the amplitude of deflection is largely dependent on the applied voltage and higher voltages (>5V) are necessary to achieve maximum deflection. At these higher voltages, water molecules begin to break down and electrolysis occurs. This is an undesirable side-effect since the activation process depends heavily on the transport of water molecules. It has been observed for some IPMC materials that when a DC voltage is applied for an extended period of time (for example, more than 30 s), the IPMC tends to relax back towards the cathode side rather than holding a constant deflection. This is thought to be the result of an increasing water concentration gradient towards the cathode side, eventually resulting in diffusion of water back towards the anode. Improvements in IPMC materials may in the future eliminate this behavior. Prior to this, to the best knowledge of the inventors, IPMC has not been exploited in the boundary layer control arena. It is extensively used as artificial muscle due to the large available bending deformations that can be obtained in a cantilever configuration at low imposed voltages and at low frequencies, of the order of 1 Hz, a frequency significantly lower than those required for boundary layer control applications. It is expected that one can employ IPMC in an innovative configuration in which the material is constrained along one surface of a sheet, leading to local, elastic deformation of the free or unconstrained surface of the exposed electrode in the presence of a time-varying electric field. Such surface modification of a sheet of IPMC is expected to enhance the existing surface roughness in a pattern determined by the particular membrane and electrode properties. IPMC is expected to be an excellent candidate material for this type of time-periodic roughness. The mechanism for strain generation in IPMC is the migration of ions across the PIEM membrane. When one side of the IPMC is constrained, for example by attachment with epoxy to a rigid (or substantially rigid) substrate, and is subjected to time-varying electrical stimuli, the corresponding frequency response observed far exceeds the typical responses observed in artificial muscle applications, in which maximum frequencies of the order of 0.1 Hz are observed because of the large deflections that are required. It is expected that responses of the order of 10 kHz can be observed under controlled conditions, which frequency exceeds the burst frequency by at least an order of magnitude or approaches the burst frequency. The magnitude of the electroosmotic pressure (and hence the surface deformations) will also be frequency dependent, according to the number of ions that can migrate through the PIEM during each half cycle of an applied electrical signal, with peak amplitudes of the order of 1 mm expected at low input frequency. It is expected based on work using IPMC in cantilevered configuration, that one should be able to measure the response of the material to pressure fluctuations in the flow of ions, with the possibility that one may be able to extract pressure information from the voltage response of the unactuated material. In specific embodiments, the electrode on at least one of the sides of the IPMC can be configured to have a plurality of individually addressable segments, so that the electric field applied in a first location of the IPMC can be controlled without regard to the field that is applied in another location of the IPMC. Using such individually addressable electrode segments, the IPMC can be controlled to provide distributed roughness in one area, and to create geometrical changes to the shape of the material in another area. It is believed that the control signals required to cause local geometrical disturbances will be larger in magnitude and lower in frequency that the signals required to cause a change in the distributed roughness over an area of a surface. In principle, there can be applied a superposition of signals, so that a selected area of the IPMC can be made to exhibit any of no change from an initial condition of roughness and shape, a change of shape alone, a change of roughness alone, or a change in both the geometrical shape and the surface roughness simultaneously. Dynamic roughness is an extremely promising application of IPMC. It is expected that the roughness amplitude can be maximized by one or all of the following methods: using larger ions for the PIEM, e.g., sodium ion rather than the smaller lithium ion; and by applying a suitable surface treatment to the exposed electrode to increase the unactuated roughness amplitude while keeping it hydrodynamically smooth, for example by sandblasting. FIG. 3 and FIG. 4 illustrate the surface morphology of an unoptimized IPMC sample before and after the final electrode deposition process, respectively. Use of platinum, the best catalytic material, for the electrodes will permit excellent control of the unactuated surface texture. In use, the roughness amplitude will be expected to be proportional to the net pressure force on the exposed electrode, and hence to the electric field, via complex mechanisms of surface electrode deformation and subject to the limitation of water electrolysis occurring at ˜1.5 V. Further increases in electric field will yield decreasing gains in amplitude and increasing heat generation. A material sample that is not optimized for this application is predicted to provide a maximum root-mean-square roughness distribution comparable to fine 600-grit sandpaper, or a 16 micron average protuberance diameter. IPMCs in cantilever configurations typically exhibit low electromechanical conversion efficiencies, of the order of 30%. While the amplitudes of motion in the current application are much smaller and hence the heat generation is expected to be reduced, the thermal cycle due to actuation must also be characterized, as an effective additional input stimulus to the boundary layer. It is believed that this can be achieved using cold-wire anemometry to describe the thermal field in the neighborhood of the IPMC strip. An additional constraint relates to the need for constant hydration of the PIEM in order to maintain ion mobility within the membrane. Initial laboratory tests indicate that evaporation losses are not important during operation under humidity conditions of the order of 10%, but a procedure to soak the strip in water between experiments to ensure full hydration and repeatable amplitudes of deformation may be important in using such materials. We now present some examples that describe in greater detail the systems and methods that have been developed. Part EXAMPLES: Experiments to evaluate the effectiveness of dynamic roughness as a control authority technique have been completed. Two different polymer candidates were evaluated and a series of baseline wind tunnel tests were performed. In one embodiment, a shape memory polymer was tested to determine its performance characteristics, including a quantification of the scale, type, and activation time of various perturbations. An example of a roughness pattern generated in the polymer was applied to a typical airfoil and tested. It was found that the applied roughness was not optimized for the boundary layer. The ubiquity of wall bounded flows in aircraft aerodynamics makes them an attractive area for research. Turbulent boundary layers, in particular, are a main focus in practical viscous flow applications. The behavior and characteristics of a turbulent boundary layer often have enormous effects on the global flow around the body. This is especially apparent on lifting surfaces where boundary layer separation may be encountered. By advantageously utilizing the pervasive nature of turbulent boundary layers, novel methods of aircraft control may be developed. It is believed that active micro flow control techniques can offer higher efficiency (in the form of lower aerodynamic penalties for a given goal, or lower energy inputs) and better performance (such as faster, more responsive control), as compared to traditional methods. Additionally, new unconventional aircraft designs may be possible without the constraints of traditional control requirements. Traditional Flow Control Traditionally, the control of aircraft has been achieved using various combinations of movable control surfaces. Through the large scale movements of these surfaces, the global flow behavior around an aircraft can be modified. Traditional control surfaces provide relatively consistent and predictable results by imparting large disturbances to the surrounding flow. These large disturbances are strategically utilized to impart moments (and thus control) to an aircraft. Although there have been variations (V-tail and flying wing aircraft), the use of control surfaces generally require a large empennage structure. Additionally, airfoils are limited in geometry due to the complex structural requirements of movable control surfaces. These necessities result in weight and drag penalties, translating to a reduction in performance and efficiency. Other large scale flow control techniques, such as vectored thrust nozzles, have more recently been employed. These methods rely on the same principle of global flow control, although in a more drastic manner. While allowing higher performance, these techniques have the same fundamental structural and performance limitations as traditional control surfaces. Micro Flow Control A different method of flow control utilizes the receptiveness of turbulent boundary layers to relatively small disturbances. This class of micro flow control includes both passive and active techniques. In contrast to control surfaces, micro flow control relies on imparting small disturbances to the boundary layer in an attempt to influence the global flow around the body. There are several flow mechanisms that can be explored ranging from the adjustment of turbulent skin friction to control of boundary layer separation. A passive micro flow technique that has been utilized effectively is the vortex generator. Although the geometries of such devices may vary, they are all based on a structure protruding slightly out of the boundary layer. This structure promotes mixing between the free stream and the circulating boundary layer flow, thus increasing boundary layer energy and delaying the onset of separation. Several active methods have also been explored. Examples of these methods include synthetic jets, heated surfaces, particle seeding, and suction. Although the mechanism utilized in each method may differ, they share a common underlying principle. These methods all rely on injecting energy to the boundary layer, making it more robust to separation. The application of synthetic jets involves an array of pressurized micro jets (often embedded in the surface of a body) that inject bursts of fluid into the boundary layer. In contrast, suction methods rely on a porous surface in which fluid is extracted from the boundary layer. In both cases, circulation in the boundary layer is increased thus delaying the decay of kinetic energy leading to separation. Heated surfaces increase the energy in the boundary layer by simply adding a heat flux to the flow. Particle seeding relies on injecting small particles into the boundary layer to encourage mixing between the free stream and circulating regions (much like vortex generators). Although all of these methods have been proven in the lab, only the synthetic jets have proven viable enough to use in practice. In a NASA headed project, a V-22 Osprey tilt rotor aircraft was fitted with a line of synthetic jets to help mitigate sudden boundary layer separation in the vertical lift configuration. All active methods used thus far have two distinct disadvantages. First, they address only a single, narrow flow regime near separation. Second, they all require complex underlying structures such as plumbing networks and compressors/pumps. These weaknesses may limit the useful extent of these micro control methods. The systems and methods of the present invention involve boundary layer control using surface modulation, or more specifically dynamic roughness. The major advantage of surface modulation techniques over existing micro flow control methods is that they do not require the same intricate underlying structures and plumbing. This allows the technique to be more readily applied to existing and to near future applications. Successful implementation of this method is expected to provide improved and more efficient flight control. Furthermore, its advantages over traditional control methods may allow unconventional aircraft designs that were impossible before. Theory Surface Modulation and Dynamic Roughness Surface modulation as a micro flow control device allows a wide variety of application techniques. With proper material technologies, a vast number of dynamic boundary conditions can be envisioned, such as continuous, wave like surfaces or arrays of discrete perturbations. In all cases, the overall goal is to trigger a large, global flow change with a relatively small mechanical surface modulation, in the form of dynamic roughness that can be accomplished with a low energy input. By dynamically roughening the surface, the characteristics of the turbulent boundary layer may be altered. We seek to use this method to impart control authority (that is, the ability to control the fluid dynamic forces on a surface and the resulting motion of an object comprising that surface) through a wide regime, rather than only addressing the flow regime near separation. Control authority can be achieved by applying either detrimental or beneficial effects to the boundary layer. By roughening the surface, it has been empirically shown that skin friction increases and the boundary layer can be driven towards separation. Real world applications of these effects can be observed in cases of aircraft icing as well as observations of the effect of insect covered wing surfaces. While increasing skin friction is a sure method of extracting control authority, it carries a significant penalty in the form of increased overall drag. In contrast, the strategic addition of roughness to a surface has also been shown to decrease skin friction by driving the boundary layer towards the brink of separation. By driving a boundary layer towards separation, but not allowing it to actually fully separate, the total skin friction on the surface is decreased. This method is more complicated than simply increasing skin friction since a fine balance between avoiding full separation and maintaining lower wall shear stress must be met. This mechanism is the idea behind Stratford's well-known zero skin friction airfoil profile. Stratford demonstrated that a specific airfoil shape resulted in zero skin friction over the foil's adverse pressure region, and thus improved efficiency. However, the nature of the foil required operation within a very narrow flow regime. It is believed that the application of dynamic surface modulation techniques can provide similar behavior over a robust range of flow regimes. Such a dynamic system may require feedback control in implementation, for example by the application of motion sensors operative along as many as three axes and suitable computer control systems comprising general purpose programmable computers and software. If either mechanism is applied asymmetrically to a body (i.e.; either by application of one effect on one wing, or by application of opposite effects on opposite wings of an aircraft) a control moment (roll, pitch, or yaw) may be achieved. In order to increase the effectiveness of the application of dynamic roughness, we seek to operate in a flow regime that is most receptive to boundary condition changes, so that the performance of an airfoil changes significantly with relatively small changes in the boundary surface. In the flow regime centered around Reynolds number Re=105 over two orders of magnitude in performance change is possible. Material Properties Important parameters that play a role in determining the utility of a given material for providing a surface that exhibits dynamic roughness include the receptivity of the material to shape and texture perturbations, the energy required to activate the material, and the dynamic response time of the material. It is advantageous to be able to quickly activate (and deactivate) various roughness patterns while consuming as little power as possible. Two types of materials that have been analyzed for this purpose are one or more shape memory plastics produced by Cornerstone Research Group (CRG) of 2750 Indian Ripple Rd., Dayton, Ohio 45440, and an ionic polymer metal composite (IPMC) produced by Environmental Robots, Inc. Some of CRG's current shape memory plastic formulations are based on styrene acrylate, cyanate ester, and epoxy polymer systems. Shape Memory Polymer Exotic shape memory metals, such as a nickel-titanium alloy known as Nitinol (originally developed at the United States Naval Ordinance Laboratory and available in various compositions), have long been used for their ability to switch between pliable and rigid states. However, these alloys carry several disadvantages such as a fixed, high activation temperature (hundreds of degrees Celsius), relatively minor deformation (on the order of 10%) and high manufacturing cost. More recently, shape memory characteristics have been achieved using special blends of polymers. By tailoring different types and amounts of a given polymer component, the activation temperature can be varied. Additionally, the polymers produced can be deformed by several hundred percent while being relatively low cost to produce. Shape memory polymers achieve their characteristics using varying blends of a copolymer element and a comonomer element. The base copolymer generally comprises crosslinked hard and soft segments (with high and low glass transition temperatures, respectively) and is responsible for switching between and holding rigid crystallized states. The purpose of the comonomer is to adjust the glass transition temperature of the shape memory polymer. When the mixed material is heated to the combined glass transition temperature of the copolymer and comonomer combination, determined by the Fox equation, it becomes pliable. By adjusting the ratio of the comonomer to the copolymer, thereby changing the total glass transition temperature, the final transition temperature of the shape memory polymer can be changed. Furthermore, the amount of deformation and final rigidity of the polymer can be tailored by varying the extent of the comonomer. Typical shape memory polymers (used primarily in medical suture applications) comprise an oligo(e-caprolactone) dimethacrylate copolymer structure and n-butyl acrylate as the comonomer (due to its low glass transition temperature of −55° C.). We have examined CRG Veriflex®, which is a proprietary blend of styrene acrylate, cyanate ester, and other epoxy polymers. From the material properties of the individual components it can be inferred that the styrene acrylate copolymer composes the base material (the polymer has a typical glass transition temperature of 55 to 65° C.). Cyanate ester is a curable resin with a high (288° C.) transition temperature. Its most likely role is a strengthening component while also allowing the product to be sold as a two part resin system. According to CRG (see http://www.crgrp.net/veriflex.shtml), the polymer is capable of a 200% deformation at a glass transition temperature of 62° C., while transition temperatures ranging from −30° C. to 260° C. have been observed. In its rigid state, the polymer has a tensile, compressive, and flexural strength of 22.8 MPa, 32.4 MPa, and 31.7 MPa respectively. The thermal conductivity (at 18.9° C.) of the material is stated to be 0.17 W/(m·K). One limitation of current commercially-available shape memory polymers is that they only give a one-way actuation and therefore require a mechanical input to return to the undisturbed configuration. Ionic Polymer Metal Composite Various electroactive polymers (EAP) have been employed as electrically controlled actuators, particularly in the study of artificial muscles. EAPs are typically light weight and can deform by a significant amount under relatively low power application. IPMC samples initially required activation to occur while submersed in a solvent (water). When exposed to air, the effectiveness of the polymer would then drop drastically after a few minutes. However, a coating has been applied to some samples that allows the polymer to activate in air for months. The performance of these polymers still relies on the moisture content in the surrounding air. The IPMC sheets provided by Environmental Robots, Inc. and used by the inventors are Nafion® 117 based and can be activated in air. Facility and Equipment Experimental observations were conducted at Caltech's Graduate Aeronautics Laboratory (GALCIT). All data was recorded in the Blue Tunnel facility. The closed loop wind tunnel has a 0.61 m by 0.61 m by 2.1 m test section and is capable of a 50 m/s maximum flow speed. Mean velocity measurements will be conducted with a pitot tube sufficiently far from the test article. The flow temperature is controlled to ensure operation at a consistent Reynolds number regime. The test article is suspended from the roof of the test section with the roof acting as a bounding wall on one tip of the foil (the other tip is free). An optical rotary mount allows the foil to be swept through a range of angles of attack with a resolution of half a degree. Force and moment data was recorded using a custom 3-component force balance. The balance is aligned such that one force transducer is aligned with the direction of flow (giving a drag force) while two are aligned normal to the free stream (the sum of the two signals gives total lift while the difference is proportional to a pitching moment). The drag transducer has a maximum load of 44.5 N while each lift cell is capable of 222 N (444 N total lift). However, it was found during calibration that the balance begins to display non-linear behavior at total loads greater than 70% of full scale in both drag and lift directions. Raw and calibrated data was recorded using custom acquisition software written in National Instruments' LabView environment. The balance was initially calibrated on a test stand by hanging known weights in the drag and both lift directions. The calibration force was applied at half span (approximate center of force) of a calibration spine with similar dimensions as the test article. Measurements Using Shape Memory Polymer Cornerstone Research Group offers the tested shape memory polymer as a two part resin system under the trade name Veriflex®. The resin is injected into a closed mold and subject to a heating cycle to fully cure. According to CRG, the resin may be cast into sheets with a maximum thickness of 1.27 cm (with no restriction on minimum thickness). Testing has demonstrated that the effective minimum thickness is 1.6 mm. Curing was inconsistent and resulted in a brittle polymer when thinner sheets were molded. CRG advises that the polymer should be cured between two sheets of glass (separated by Viton cord) to assure even heating. Since it is difficult to machine glass (to allow molds with different geometries), tests were conducted curing the resin using Teflon and aluminum molds. It was found that Teflon sheets 0.635 mm thick did not have a sufficiently uniform flat surface to allow consistent curing. Additionally, the Teflon molds deformed slightly during the curing process allowing air into the resin. Aluminum molds of the same thickness (0.635 mm) resulted in a cure quality similar to glass molds. To generate embedded roughness patterns, the shape memory polymer was molded using premachined aluminum plates (see FIG. 5). In the first mold, grooved channels (corresponding to ridges in the resulting polymer sheet) of varying depths (see Table 1 below) were machined using a ⅛ inch end mill. The second mold consisted of dimples drilled into the aluminum using standard bits (#54, #44, and #24 bits corresponding to range of bump diameters in Table 1). The dimples were drilled to a depth corresponding to the standard taper at the end of each bit. For each bump diameter, two rows of 10 bumps were machined with the second row laterally offset from the first by half the bump spacing (as given in Table 1). FIG. 5 is an image of an aluminum mold used for generating roughness pattern in shape memory polymer. Two amplitudes shown, both with density λ=0.1 Due to the method utilized for creating the roughness molds (used to cast shape memory polymer sheets), the exact amplitude is determined by the availability of standard twist drill bit sizes. In order to achieve the desired conical geometry for each roughness bump, only the tapered tip of the bit is used in creating the mold indentations (see FIG. 6). FIG. 6 is a drawing that illustrates standard twist drill bit tip geometry. Since the point angle is defined to be a standard 118°, the necessary bit diameter can be calculated from a desired amplitude. The closest matches to the 1.0 mm and 0.5 mm desired amplitudes correspond to #30 and #51 gauge bits respectively. These bit diameters will yield actual amplitudes of 0.98 mm and 0.51 mm. In addition to mold material, the curing process also depends on the baking temperature and baking time. CRG recommends curing at 75° C. for 36 hours. It was found during testing that the process is relatively insensitive to excess cure times (up to 48 hours) but higher cure temperatures (above approximately 90° C.) resulted in brittle polymer sheets. All performance tests, with the exception of dynamic response characterization,
{'bibliographic_information': "{'country': 'US', 'doc-number': '13487496', 'kind': 'B2', 'date': '20120604', 'extension': '28', 'disclaimer_text': 'This patent is subject to a terminal disclaimer.', 'invention_title': 'Control of aerodynamic forces by variable wetted surface morphology'}", 'source_file': './grant/2013/ipg130423.xml', 'source_data': 'USPTO-Grant'}