Abstract: The present invention relates to a method for actively deforming, by feedback control, an aerodynamic profile comprising an elastic material, applied to a part of the surface of the aerodynamic profile, said elastic material being in contact with a fluid flow; said elastic material being able to be deformed by one or more shape memory actuators placed in contact with the elastic material, said actuators being controlled by a computer connected to sensors. This method applies notably to a deformation of an aerofoil of a wing of an aircraft in flight, notably subsonic.

Abstract: Metal sheets and plates having friction-reducing textured surfaces and methods of manufacturing these metal sheets and plates are disclosed herein. In an embodiment, there is provided a transportation vessel that includes at least one metal product having at least one surface that is substantially grooved, wherein the substantially grooved surface forms a riblet topography, the riblet topography including a multiplicity of adjacent permanently rolled longitudinal riblets running along at least a part of the surface, and wherein the riblet topography is coated with at least one coating sufficiently designed and applied to preserve the riblet topography. In an embodiment, the multiplicity of adjacent permanently rolled longitudinal riblets results in a friction-reducing textured surface. In an embodiment, metal product is used in fabricating at least a portion of an aircraft. In an embodiment, metal product is used in fabricating at least a portion of a rotor blade.

Abstract: An asymmetric tetrahedral vortex generator that provides for control of three-dimensional flow separation over an underlying surface by bringing high momentum outer region flow to the wall of the structure using the generated vortex. The energized near-wall flow remains attached to the structure surface significantly further downstream. The device produces a swirling flow with one stream-wise rotation direction which migrates span-wise. When optimized, the device produces very low base drag on structures by keeping flow attached on the leeside surface thereof. This device can: on hydraulic structures, prevent local scour, deflect debris, and reduce drag; improve heat transfer between a flow and an adjacent surface, i.e., heat exchanger or an air conditioner; reduce drag, flow separation, and associated acoustic noise on airfoils, hydrofoils, cars, boats, submarines, rotors, etc.

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.

Abstract: A structure includes a polymer structural member, which may include a shape memory polymer material, that can change its size and/or shape. An electromagnetic source is used to impose an electric field or a magnetic field on the polymer structural material, in order to control the shape of the material. The force may be used to change the shape of the material and/or to maintain the shape of the material while it is under load. The polymer material may be a solid material, may be a foam, and/or may include a gel. A shape memory polymer material may have mixed in it particles that are acted upon by the electromagnetic field. The structure may be used in any of a variety of devices where shape change (morphing), especially under loading, is desired.

Abstract: A wing assembly has a wing and one or more no-bias laminar flow oval diskettes that are fixed on a support structure along the C/L (center of lift) of an airfoil, of an aircraft wing. The benefit of an oval diskette with laminar flow is that it has no speed limitations and it allows an aircraft to clime at a speed that matches its Ground Effect Lift speed which is a 25% performance increase and a 40% reduction in vortex drag with a increase stability that eliminates inertia coupling of high-speed airfoils.

Abstract: The present invention is directed to the manufacture of and the use of an aerodynamic flow control device having a compact array of a plurality of fluidic actuators in planar, curved, circular and annular configurations. The compact array of fluidic actuators of the invention may be designed to produce oscillating or pulsed jets at the exit ports with frequencies in the range of 1-22 kHz. They may be integrally manufactured along with the wing sections, flaps, tail and rudder of airplane, the inlet or exit geometries of a jet engine. When supplied with a source of fluid such as air, these arrays of actuators produce a set of fluid jets of random phase of high velocity and influence the main stream of air over the subject surface. The beneficial effects of modifying flow using the present invention include increased lift, reduced drag, improved performance and noise reduction in jet engines.

Abstract: A method of using one or more microjets to create and/or control oblique shock waves. The introduction of microjet flow into a supersonic stream creates an oblique shock wave. This wave can be strengthened—by increasing microjet flow rate or the use of many microjets in an array—in order to form an oblique shock. Such an oblique shock can be used to decelerate flow in a jet aircraft engine inlet in a controlled fashion, thus increasing pressure recovery and engine efficiency while reducing flow instability. Adjusting the pressure ratio across the microjet actually alters the angle of the oblique shock. Thus, the use of microjets allows decelerating shock waves in an inlet engine to be properly positioned and controlled. Microjet arrays can also be used to ameliorate shock waves created by external aircraft surfaces, such as sensor pods and weapons.

Abstract: Systems to provide distributed flow control actuation to manage the behavior of a global flow field, are provided. An example of a system can include an aerodynamic structure having an outer surface, and an array of a plurality of nano-scale effectors connected to the outer surface of the aerodynamic structure to be in fluid contact with a flowing fluid when operationally flowing, to induce controlled, globally distributed disturbances at a viscous wall sublayer of a turbulent boundary layer of the flowing fluid when operationally flowing and to manipulate fluid behavior of the flowing fluid to thereby substantially reduce pressure loss associated with incipient separation of the fluid flow from portions of the aerodynamic structure.

Abstract: A boundary layer energizer (20) for energizing a boundary layer flow (33) over a surface (22), the boundary layer energizer (20) comprising one or more passages (24) terminating in one or more respective holes (26) provided on the surface (22), wherein the one or more passages (24) comprises at least one fin (25) configured so as to generate a vortex flow in the one or more passages (24) such that, when in use, a fluid emanating from the one or more passages (24) flows in a vortex.

Abstract: Systems and methods for controlling fluid flow utilizing a synthetic jet actuator, are provided. An example of a synthetic jet actuator system includes a synthetic jet actuator including a dual bimorph subsystem to provide low, medium, and high synthetic jet velocities and/or fine flow control response, and an arc-forming subsystem to provide enhanced pressure, velocity, and mass flow performance, enhanced flow control response, and/or heating of the fluid within the bimorph chamber to extend the performance or operating margin of the dual bimorph subsystem of the synthetic jet actuator. The arc-forming subsystem includes a pair of electrodes interfaced with inner surface walls of the dual bimorph subsystem. Various configurations of power supplies can be utilized to provide simultaneous function to both the subsystem and the arc-forming subsystem to allow selective activation.

Abstract: A high-lift device suppresses the occurrence of aerodynamic noise while minimizing an increase in airframe weight. The device includes a slat main body disposed to be able to extend from and retract into a main wing, and a concave part formed on the slat main body at a location facing the main wing and able to accommodate at least a part of a leading edge of the main wing. The device also includes an airflow control part disposed at an area in the concave part facing an upper surface of the main wing, that is accommodated between the main wing and the concave part when the slat main body is retracted into the main wing, and that suppresses turbulence colliding against the area in the concave part facing the upper surface of the main wing when the slat main body is extended from the main wing.

Abstract: Systems, method, devices and apparatus are provided for reducing drag and increasing the flight efficiency characteristics of aircraft and airships including hybrid aircraft utilizing distributed boundary layer control and propulsion devices. Boundary layer control includes passive systems such as riblet films and boundary layer propulsion devices having a divided and distributed propulsion system disposed in the curved aft sections of aircraft and airships including hybrid aircraft susceptible to boundary layer drag due to degree of curvatures, speed and density of the surrounding air. Distributed propulsion devices include constructing propellers and riblets from shape memory alloys, piezoelectric materials and electroactive polymer (EAP) materials to change the shape and length of the distributed propulsion device.

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.

Abstract: A variable porosity system for an aircraft includes a first layer, a second layer and an actuator mechanism. Each of the first and second layers has at least one pore and are slidable relative to one another. The actuator mechanism is operative to move the first and second layers relative to one another such that the pores are movable into and out of at least partial alignment with one another to allow for fluid communication therebetween. At least one of the first and second layers is substantially continuous with an outer mold line surface of an aerodynamic member such as an aircraft wing. The actuator mechanism is configured to modulate the frequency of the opening and closing of the pores with respect to flight conditions of an aircraft.

Abstract: This invention relates to a method and system (10) for controlling the boundary layer of an airfoil (12) to reduce profile drag during flap deflection. The system (10) comprises first means for blowing air from a lower surface (14) of the airfoil (12) to trip airflow from laminar flow to turbulent flow during positive flap deflection; and second means for applying a suction force at the lower surface (14) of the airfoil (12) to preserve laminar flow during negative flap deflection.

Abstract: The upstream flowfield of a vehicle traveling in supersonic or hypersonic atmospheric flight is actively controlled using attribute(s) experienced by the vehicle. Sensed attribute(s) include pressure along the vehicle's outer mold line, temperature along the vehicle's outer mold line, heat flux along the vehicle's outer mold line, and/or local acceleration response of the vehicle. A non-heated, non-plasma-producing gas is injected into an upstream flowfield of the vehicle from at least one surface location along the vehicle's outer mold line. The pressure of the gas so-injected is adjusted based on the attribute(s) so-sensed.

Abstract: Systems and methods to provide distributed flow control actuation to manage the behavior of a global flow field, are provided. An example of a system can include an aerodynamic structure having an outer surface, and an array of a plurality of effectors connected to the outer surface of the aerodynamic structure to be in fluid contact with a flowing fluid when operationally flowing, to induce controlled, globally distributed disturbances at a viscous wall sublayer of a turbulent boundary layer of the flowing fluid when operationally flowing and to manipulate fluid behavior of the flowing fluid to thereby substantially reduce pressure loss associated with incipient separation of the fluid flow from portions of the aerodynamic structure.

Abstract: A micro-electromechanical system (MEMS) dielectric barrier discharge (DBD) based aerodynamic actuator is configured to modify a shockwave boundary layer interaction and limit incident boundary layer growth caused by a reflected shockwave.

Abstract: A wing of an aircraft has a mainplane, which has an upper face, a lower face and an aerodynamically shaped area. The wing has an additional airfoil which is articulated on the mainplane and can be extended from a retracted state with a slot area being opened between the mainplane and the additional airfoil. The wing also has a variable-position slot-varying apparatus which is arranged on the lower face, forms a part of the aerodynamic profile of the additional airfoil or mainplane when the additional airfoil is extended, and at least partially covers the slot area between the mainplane and the additional airfoil on the lower face when the additional airfoil is in the retracted state. The slot-varying apparatus can be varied between a curved configuration, in which it forms a part of an aerodynamic profile, and an extended configuration, in which it at least partially covers the slot area.

Abstract: A solid-fuel pellet thrust and control actuation system (PT-CAS) provides command authority for maneuvering flight vehicles over subsonic and supersonic speeds and within the atmosphere and exo-atmosphere. The PT-CAS includes a chamber or solid-fuel pellets that are ignited to expel gas through a throat. The expelled gas is directed at supersonic vehicle speeds in atmosphere to a cavity between an aero control surface and the airframe to pressurize the cavity and deploy the surface or at subsonic speeds in atmosphere or any speed in exo-atmosphere allowed to flow out a through-hole in the surface where the throat and through-hole provide a virtual converging/diverging nozzle to produce a supersonic divert thrust. A pellet and control actuation system (P-CAS) without the through-hole provides command authority at supersonic speeds in atmosphere.

Abstract: An aircraft with an outer surface from which flows an aerodynamic stream of cold air and includes at least one hot gas outlet, characterized in that it includes at least one device (16) for generating aerodynamic disturbances so as to mix hot gas and cold air, whereby the at least one device is connected to an outer surface (10) for protection against the heat and/or close to a hot gas outlet (12).

Abstract: A system and method for control of a fluid flow. The system includes an array of interdependent fluidic actuators, each including a chamber, a flow control port, and opposite side walls configured to expand apart and contract together to flow a control fluid through the flow control port in response to an input, wherein adjacent actuators in the array of interdependent fluidic actuators are integrally coupled together via a common side wall of the opposite side walls.

Abstract: A purging system for a laminar flow control system comprises an air scoop and a diffuser fluidly connected thereto. The air scoop is disposable into an external flow of an external atmosphere. The diffuser is configured to fluidly connect the air scoop to a suction cavity of the laminar flow control system wherein the suction cavity may be disposed adjacent a porous skin of an airfoil such as adjacent a leading edge of the airfoil. The laminar flow control system may be configured to suction boundary layer flow passing over the porous skin by drawing a portion of the boundary layer flow through a plurality of pores formed in the porous skin. The diffuser ducts high pressure flow captured by the air scoop to the suction cavity for discharge through the pores to reduce the potential of blockage thereof.

Abstract: A rotary-wing system which generates a directed ion field to propel a fluid along a rotary-wing to control at least one boundary layer characteristic.

Abstract: A system and method is described generally for deforming a surface of a body to alter a fluid flow in order to change the characteristics of the fluid flow about the body.

Abstract: A system and method is described generally for deforming a first surface of a body and deforming a second surface of a body to alter a fluid flow in order to change the characteristics of the fluid flow about the body and thereby control the fluid dynamic forces on the body.

Abstract: The present invention provides a system and method for actively manipulating and controlling aerodynamic or hydrodynamic flow field vortices within a fluid flow over a surface using micro-jet arrays. The system and method for actively manipulating and controlling the inception point, size and trajectory of flow field vortices within the fluid flow places micro-jet arrays on surfaces bounding the fluid flow. These micro-jet arrays are then actively manipulated to control the flow behavior of the ducted fluid flow, influence the inception point and trajectory of flow field vortices within the fluid flow, and reduce flow separation within the primary fluid flow.

Abstract: A system and method for generating lift provided by a multi-element aircraft wing are provided. The system includes a main wing element, a slat interconnected to the main wing element, and a flap interconnected to the main wing element. The system also includes at least one port defined in at least one of the slat, main wing element, and flap. In addition, the system includes at least one fluidic device operable to regulate fluid flow into and out of the at least one port to control boundary layer flow over at least one of the slat, main wing element, and flap.

Abstract: Air induction control systems and methods for aircraft are provided. A particular aircraft includes a fuselage, a pair of wings and an engine. The aircraft also includes an inlet defining an aperture to receive air for delivery to the engine. The inlet has a longitudinal axis generally aligned with a direction of flow of the air as the air approaches the inlet. The aircraft also includes at least one first dielectric barrier discharge generator positioned to apply a first force to the air prior to the air being received by the engine. The first force acts in a first direction. The aircraft further includes at least one second dielectric barrier discharge generator positioned to apply a second force to the air prior to the air being received by the engine. The second force acts in a second direction that is non-parallel to the first direction.

Abstract: The present invention provides a system and method for actively manipulating fluid flow over a surface using synthetic pulsators. Synthetic pulsators produce pulsed jet operable to manipulate the primary fluid flow proximate to the synthetic pulsator. The synthetic pulsator includes a synthetic jet actuator(s) located within an ambient pressure chamber, wherein the synthetic jet actuator is operable to produce an oscillatory flow. The oscillatory flow of the synthetic jet(s) produces the pulsed jet operable to manipulate the primary fluid flow. These synthetic pulsators may then be actively manipulated to control the flow behavior of the ducted fluid flow, influence the inception point and trajectory of flow field vortices within the fluid flow, and reduce flow separation within the primary fluid flow.

Abstract: Deployable aerodynamic devices with reduced actuator loads, and related systems and methods are disclosed. An external flow system in accordance with a particular embodiment includes an external flow body, a deployable device carried by and movable relative to the external flow body, and a coupling connected between the external flow body and the deployable device. The system can further include an actuator device operatively coupled between the external flow body and the deployable device, with the actuator device positioned to move the deployable device along a motion path between a stowed position and the deployed position. The motion path can have a first portion over which the load delivered by the actuator device increases as the deployed device moves toward the deployed position, and a second portion over which the load delivered by the actuator device decreases as the deployed device moves toward the deployed position.

Abstract: The present application describes to a deflection device, for example, for a blunt stream body. The deflection device has an edge, which, for example, can be mounted to the stream body. In an advantageous manner, the deflection device allows an influencing of the slipstream in such a way that turbulences, which are connected with the slipstream and form downstream of blunt stream bodies, have as little influence as possible on the dragged object in order to avoid the formation of building-up motions of the dragged object, which lead to instabilities.

Abstract: A device for controlling a vortex trail generated by an oblong element of an aircraft bearing surface includes a control component arranged on a fixing element of the oblong element and on a bearing surface such that a base of the control component contacts the leading edge of the bearing surface. The control component has a triangular shape, on a plane perpendicular to the longitudinal axis thereof, whose two adjacent sides form flanks interconnected by a rounded edge.

Abstract: A fluid dynamic section provides one or more fixed size escapelets through a foil body to reduce the induced and interference drag caused by trailing vortices and similar wake turbulence. The escapelets, which can be provided in both aerodynamic and hydrodynamic structures, such as wings, tail sections; rotary blades, guy wire frames, wing sails, and various underwater keels and wing keels. The escapelets transfer energy from an inlet located in the high-pressure surface of the foil or foil body to an outlet located in the lower-pressure surface, allowing energy that would normally form a vortex at the tip of the foil to be redirected and dissipated in a beneficial way. As a result, drag is reduced and fuel economy is increased, while at the same time increasing the authority of ailerons and similar flight control surfaces, allowing aircraft that were not previously spin recovery rated to become spin recoverable.

Abstract: An onboard system for a rotary wing aircraft detects a limit cycle oscillation in the tail mast and provides a timely indication of the limit cycle oscillation to an aircrew before serious damage to the airframe is likely to occur.

Abstract: Systems and methods to provide distributed flow control actuation to manage the behavior of a global flow field, are provided. An example of a system can include an aerodynamic structure having an outer surface, and an array of a plurality of effectors connected to the outer surface of the aerodynamic structure to be in fluid contact with a flowing fluid when operationally flowing, to induce controlled, globally distributed disturbances at a viscous wall sublayer of a turbulent boundary layer of the flowing fluid when operationally flowing and to manipulate fluid behavior of the flowing fluid to thereby substantially reduce pressure loss associated with incipient separation of the fluid flow from portions of the aerodynamic structure.

Abstract: The invention relates to a flying object which moves with a transonic or supersonic velocity. The inventive flying object comprises a main body, a streaming element and a holding element. The holding element holds the streaming element distant from the main body. The streaming element is permeable for the airstream. For one embodiment the streaming element is built with a porous material. The streaming element has an outer surface with the shape of a cone or a truncated cone. The holding element holds the streaming element in an orientation with the cone opening towards the airstream.

Abstract: A flow surface (16), e.g. on a swept aircraft wing, has a three-dimensional boundary-layer flow. The surface is defined by a spanwise direction (z) and a chordwise direction (x). In or on the flow surface excitation locations (22) are arranged, exciting primary disturbances. The disclosure is characterized in that the excitation locations (22) are arranged such that benign steady primary disturbances are excited and maintained on a sufficiently-high amplitude level as longitudinal vortices respectively crossflow vortices, suppressing naturally growing nocent primary disturbances by a non-linear physical mechanism. The benign primary disturbances preserve a laminar flow, such that unsteady secondary disturbances, which may initiate turbulence and which, otherwise, are excited in streamwise direction by nocent primary vortices, are suppressed or at least stabilized.

Abstract: Aircraft exhaust systems and methods are disclosed. In one embodiment, an integrated propulsion assembly includes a wing assembly having an upper surface and a lower surface, and a propulsion unit at least partially disposed within the wing assembly. An exhaust system is configured to conduct an exhaust flow emanating from the propulsion unit to an exhaust aperture. The exhaust aperture is positioned proximate a trailing edge of the wing assembly, and has an aspect ratio of at least five. In further embodiments, the wing assembly includes a flap member moveably coupled along a trailing edge portion of the wing assembly, and the exhaust aperture is configured to direct the exhaust flow over at least a portion of the flap member.

Abstract: The present invention provides a system and method for actively manipulating fluid flow over a surface using synthetic pulsators. Synthetic pulsators produce pulsed jet operable to manipulate the primary fluid flow proximate to the synthetic pulsator. The synthetic pulsator includes a synthetic jet actuator(s) operable to produce an oscillatory flow, and fluidic jet(s) operable to provide a continuous fluid flow. The oscillatory flow of the synthetic jet(s) and the continuous fluid flow of the fluidic jet(s) combine or mix to produce the pulsed jet operable to manipulate the primary fluid flow. These synthetic pulsators may then be actively manipulated to control the flow behavior of the ducted fluid flow, influence the inception point and trajectory of flow field vortices within the fluid flow, and reduce flow separation within the primary fluid flow.

Abstract: In order to establish laminar flow on the attachment line (18) of an aerofoil body, a duct entrance (27) is provided on the leading edge of the aerofoil body for receiving spanwise boundary layer flow BLt. The exit (23) of the duct is located spanwise downstream of the duct entrance (27). The boundary layer flow BLt enters the duct (23) and is discharged downstream. The height of the duct entrance (27) above the leading edge of the aerofoil body is greater than the depth of the boundary layer BLt and thus a fresh laminar boundary layer is established on the outer surface (20) of the duct which propagates spanwise along the surface to rejoin the leading edge of the aerofoil body.

Abstract: Methods and apparatus for controlling the attitude of a mobile platform with a resolution suitable for vernier attitude control. In one embodiment a method includes flowing fluid through an orifice of an aerodynamic surface. The method also includes modifying a boundary layer of the aerodynamic surface with the flowing fluid. Another embodiment provides an aerodynamic member of a mobile platform. The aerodynamic member includes an aerodynamic surface, an orifice, an actuator, and a fluid moving member. The orifice is in the aerodynamic surface and the actuator is subject to friction and backlash. The fluid moving member communicates with the orifice and causes the fluid to flow through the orifice to modify the boundary layer of aerodynamic surface.

Abstract: An air induction system for an aircraft to control distortion and pressure recovery for improved aerodynamic performance. The system includes an inlet and at least one dielectric barrier discharge generator positioned upstream of the engine for imparting momentum to a low-energy boundary layer of air. A plurality of spaced dielectric barrier discharge generators may be activated in selected combinations to optimize performance at respective flight conditions. In one embodiment, one or more generators may be oriented generally transverse relative to the flow of intake air to eject the boundary layer in a lateral direction and prevent its ingestion by the engine. In another embodiment, one or more generators may be oriented along the direction of flow to accelerate the boundary layer air.

Abstract: The nacelle drag reduction device comprises a substantially circular and axis symmetrical external airfoil concentric with a aft section of the nacelle and located outside a propulsive jet zone defined behind the engine when operating, the airfoil being positioned at a location providing a maximum streamline angle with reference to the main axis of the engine and a highest streamline curvature.

Abstract: Aerodynamic high-performance profile (10), in which, to force a turbulent flow of the boundary layer away from the bottom side (12), a transition strip (16), which extends over the entire length of the rear edge, is situated in direct proximity to the rear edge (15).

Abstract: Systems, equipment, and methods to deposit energy to modify and control air flow, lift, and drag, in relation to air vehicles, and methods for seeding flow instabilities at the leading edges of control surfaces, primarily through shockwave generation through deposition of laser energy at a distance.

Abstract: Systems and methods for controlling air vehicle boundary layer airflow are disclosed. Representative methods can include applying electrical energy bursts and/or other energy bursts in nanosecond pulses in the boundary layer along a surface of an air vehicle. In a particular embodiment, electrical energy is discharged into the boundary layer to reduce the tendency for the boundary layer to separate and/or to reduce the tendency for the boundary layer to transition from laminar flow to turbulent flow. In other embodiments, energy can be discharged via pulses having a pulse width of about 100 nanoseconds or less, and an amplitude of about 10,000 volts or more. Actuators discharging the energy can be arranged in a two-dimensional ray of individually addressable actuators. Energy can be delivered to the boundary layer via a laser emitter, and energy can be received in a receiver after having transited over at least a portion of the airflow surface.

Abstract: The present invention provides a system and method for actively manipulating and controlling aerodynamic or hydrodynamic flow field vortices within a fluid flow over a surface using micro-jet arrays. The system and method for actively manipulating and controlling the inception point, size and trajectory of flow field vortices within the fluid flow places micro-jet arrays on surfaces bounding the fluid flow. These micro-jet arrays are then actively manipulated to control the flow behavior of the ducted fluid flow, influence the inception point and trajectory of flow field vortices within the fluid flow, and reduce flow separation within the primary fluid flow.

Abstract: In aeronautical devices where a fluid such as air flows over a surface (1) to create lift or thrust, improved performance can be obtained by energising a so-called 5 “boundary layer” (10) of the fluid flow close to the surface. This is known to help prevent separation of the fluid flow stream from the surface thereby maximising the lift or thrust achieved. The invention provides a facility (7A) for controlling the mechanisms (7) used for energising the boundary layer so as to selectively increase or decrease the effect 10 in different areas. When this is done for example on different sides of an air vehicle, it provides an effective mechanism for steering the vehicle.