Abstract: Method and apparatus for suppressing fluid flow separation from a surface of a body during flow of a fluid along the surface of the body. At least one barrier member (for example, at least one tab) is provided extending away from the surface of the body and into a separated flow region adjacent the body surface, but not into a smooth flow region beyond the separated flow region. Where a plurality of barrier members are used, the barrier members are located spaced from each other along the direction of flow of the fluid. The barrier member suppresses upstream movement of the separation point between smooth flow along the body surface and separated flow. A chamber extending from the body surface and into the body can be positioned at the barrier member, to provide a place for vortices in the fluid flow to settle down. The barrier member can be moved from a position where it is co-planar with the body surface to a position where it extends away from the surface into the separated flow region.

Abstract: An apparatus to modify a wing to provide increased lift over drag ratios compared to similar wings with straight leading edges. For wings extending in a lateral direction, and defining a longitudinal upstream direction, the apparatus forms a laterally extending leading edge facing in the upstream direction. The apparatus forms a plurality of protrusions spaced laterally along the leading edge, the protrusions creating a smoothly varying, alternately forward-and-aft sweep along the leading edge relative to the upstream flow direction along the leading edge.

Abstract: One aspect of the apparatus disclosed herein is a system for modifying an aerodynamic property of an aerodynamic surface in a fluid flow. The fluid flow could comprise a free stream fluid flow, or an internal fluid flow, such as in a nozzle, diffuser, or compressor. The system of the preferred embodiment comprises a synthetic jet actuator embedded in an aerodynamic surface. In one aspect, the aerodynamic surface may be a wing. The synthetic jet actuator typically has a jet housing defining a chamber, where the chamber is in fluid communication with the fluid. This fluid communication may be accomplished via an orifice in a wall of the housing. Additionally, a portion of said housing is preferably moveable such that the volume of the chamber can be adjusted. The system also comprises a device for changing the position of the moveable portion of the housing at a predefined frequency. In this way, the synthetic jet actuator is pulse modulated in order to enhance the synthetic jet actuator's performance.

Abstract: A series of parallel riblets extend from a smooth, aerodynamic surface for reducing the skin friction drag of the surface an airstream flows around it. The riblets extend longitudinally along the surface and have a triangular cross-section in the transverse direction. The apex of the cross-section defines a continuous, undulated ridge with peaks and valleys. Measured from the surface, the peaks have a greater height than the valleys. The interaction of the riblets with the structure of the turbulent boundary layer of the airstream reduces the skin friction drag coefficient of the surface by approximately 12% over an identical smooth surface without the riblets. This reduction occurs despite the significant increase in wetted area of the riblet-covered surface over the smooth surface.

Abstract: A body driven through air or other fluid has a surface including a plurality of similar wave-shaped elements, each having a curved nose connected to an extended tail. Each element extends substantially across the body and the elements are located in parallel relationship and generally oriented across the path of the air. The adjacent elements may be connect tail to nose or may be spaced with a flat surface connection or a small modified surface connection between individual elements or groups of elements.

Abstract: Tabs are placed on a moving object in order to de-organize the fluid or air, passing over the moving object. The tabs can be any type of protrusion on the body of the moving object. The placement, size, and number of tabs depends on the size and contour of the moving object and can be optimized by testing. The use of these tabs causes less friction between the fluid or air and the object, and increases the efficiency and stability of the moving object. Additionally, dimpled strips can be used to de-organize the fluid in lieu of tabs.

Abstract: The invention is a structure for inhibiting the turbulence phenomena of a fluid, exhibiting a surface geometry comprising at least one series of inhibition surfaces which inhibit turbulence present in a boundary layer of the fluid in proximity to the wall of the structure and which extend substantially longitudinally in the direction of flow of the fluid. The inhibition surfaces comprise at least a first series of surfaces (01) of amplitude a1 and at least a second series of surfaces (02) of amplitude a2. The second series of surfaces (02) is arranged so as to be superposed on the first series of surfaces (01), the first series of surfaces (01) allowing inhibition of at least turbulence of great amplitude and the second series of surfaces (02) allowing inhibition of at least turbulences of low amplitude. The structure has an application for forming at least part of a pipe for conveying a pressurized gas.

Abstract: A system and method for analyzing physical parameters of flight data at a plurality of discrete locations about a surface of an aircraft includes a multisensor system having an array of belts. Each belt includes a plurality of interconnected belt segments including a substrate having an electrically conductive digital data bus, and at least one module having a first sensor, a second sensor and a digital signal processor, and a coating for protecting the belt segment. The first and second sensors, which are preferably formed as microelectromechanical sensors sharing a common substrate, respectively generate signals representative of a first physical parameter and a second physical parameter. The processor receives and analyzes the first and second signals to generate a third signal. The third signal is transmitted along the electrically-conductive bus to a remotely-located controller.

Abstract: A surface for contact with a fluid, flowing in a flow direction (A) over the surface, is provided with grooves (1) to prevent flow separations at low, local Reynolds numbers. The grooves extend between an upstream-directed, closed groove entrance and a downstream-directed, open groove exit and are inclined to the flow direction (A), at least in the vicinity of the groove entrance.

Abstract: A supersonic ground vehicle having a housing configured from a pair of back-to-back symmetric housing components, and a shock-reflecting surface which extends in the direction of travel of the housing and which aerodynamically interacts with the housing to form a supersonic biplane, thereby substantially reducing aerodynamic pressure drag.

Abstract: A body moving through a fluid has air control and directing elements on its outer surface. The elements are laterally and longitudinally spaced and includes elements having a forward curved nose or front portion and tapered tail portions projecting outwardly from the main body. Each of the elements and body space between the elements is covered with parallel ribs extending parallel to the elements. Special elements may include raised flexible tail portions for further interacting with the air or other fluid. The shape of the elements and the ribs are varied in accordance with the desired interaction with the fluid to create the multi-dimensional fluid movement over the surface. Various different shapes and configurations of the elements are described.

Abstract: A surface (2) is intended for a wall which is subject to a turbulent flow with a main direction of flow. The surface (2) has projecting ribs (6) oriented in the main direction of flow and spaced laterally to the main direction of flow. The height (8) of the ribs is in the range of 45% to 60% of the lateral distance between the ribs. The ribs (6) are wedge-shaped with a wedge angle (7) in the range of 20.degree. to 50.degree..

Abstract: A method is provided for hypersonic laminar flow control which uses the effect of boundary layer stabilization by an ultrasonically transparent coating. A hypersonic body surface is covered by the coating which absorbs the flow disturbance energy and does not trip the boundary layer flow. In one embodiment, the coating is made from a porous material of regular structure containing cylindrical blind microholes normal to the body surface. In another embodiment, the porous material has random distributions of pore shape and orientation. Extraction of the flow disturbance energy by pores causes stabilization of the boundary layer on the coated surface and leads to laminar-turbulent transition delay. The method can be used to decrease the aerodynamic drag of hypersonic vehicles and reduce heat transfer on vehicle surfaces.

Abstract: The invention relates to a surface of a body exposed to circumfluent fluid with elevations protruding from the base surface.In order to design the surface of a body exposed to circumfluent fluid with elevations protruding from the base service with an even more favorable flow, it is provided that when the surface is viewed from the top the elevations are bordered in each case by two boundary lines of which the one boundary line is longer and possesses a greater curvature than the other boundary line so that the cross-section area of an airfoil is produced.

Abstract: An article for reducing the drag caused by a fluid flowing over a surface comprises an outer layer having an exposed patterned surface that reduces drag, an inner reinforcing layer, and an intermediate layer for bonding the outer layer to the reinforcing layer.

Abstract: In one embodiment for a helicopter main rotor assembly, a half-plow vortex generator is mounted in combination with the upper aerodynamic surface of each main rotor blade and is operative to generate a primary corotating vortex of sufficient strength to interact with and accelerate the dissipation of the tip vortex generated by the same main rotor blade, thereby reducing blade-vortex interaction noise radiating from the helicopter main rotor assembly. The half-plow vortex generator has a right triangular planform configuration defined by a length, a width, and an apex angle. The three-dimensional configuration of the vortex generator is further defined by an apex height. The apex height is the primary determinant of the strength of the generated primary corotating vortex and is defined in terms of the thickness of the main rotor blade at the local chord where the vortex generator is mounted.

Abstract: In one embodiment for a helicopter main rotor assembly, a half-plow vortex generator is mounted in combination with the upper aerodynamic surface of each main rotor blade and is operative to generate a primary corotating vortex of sufficient strength to interact with and dissipate the tip vortex generated by the same main rotor blade, thereby reducing blade-vortex interaction noise radiating from the helicopter main rotor assembly. The half-plow vortex generator has a right triangular planform configuration defined by a length, a width, and an apex angle. The three-dimensional configuration of the vortex generator is further defined by an apex height. The apex height is the primary determinant of the strength of the generated primary corotating vortex and is defined in terms of the magnitude of the local chord where the vortex generator is mounted. The apex height preferably has a magnitude within the range of about 0.01 to about 0.08 of the magnitude of the local chord.

Abstract: A vortex generator for attenuating flow separation which occur during supersonic flow of air over structure such as an aircraft airfoil, its fuselage, surfaces forming a part of a jet propulsion unit, turbine or compressor blades, or similar surfaces subjected to supersonic airflow. A series of vortex generators are provided each of which comprises a cavity in the component over which the supersonic air is flowing that is configured to generate a spiral vortex which attenuates flow separation and weight drag resulting from the supersonic airflow. Each cavity is of generally triangular configuration defined by two side walls which diverge in a direction away from the apex of the triangular cavity, and a flat bottom wall joined to the side walls. In an alternate embodiment, means is provided for selectively shifting the bottom wall from a retracted inner position, to an outer location essentially flush with the surface over which the supersonic airflow is occurring.

Abstract: The invention is directed to an apparatus for attaching to a wing operating in a fluid medium for increasing the angle of attack at which the wing experiences aerodynamic/hydrodynamic stall. The wing includes upper and lower surfaces extending between a leading edge and a trailing edge and having a maximum thickness therebetween, and between a root and a tip, wherein the leading and trailing edges define a chord and the root and tip define a span. The apparatus comprises at least one substantially triangular shaped plate member projecting normal to the upper surface of the wing. The at least one plate member has a straight top surface and a curvilinear bottom surface which corresponds to the contour of the upper surface of the wing. The top and bottom surfaces define the height of the at least one plate member and extend in a substantially chordwise direction between an anterior end and a posterior end of the at least one plate member.

Abstract: Measures are disclosed for modifying the boundary layer flow over fluid dynamic surfaces using patterns of riblets which are set at a peak-to-peak spacing substantially less than 80 wall units and which are provided with boundary layer suction means comprising apertures (A) between the riblets for a combinative improvement of boundary layer flow. In a further aspect, riblets are employed in combination with wall apertures as an improved means of shock wave (W) control by permitting recirculation of boundary layer fluid from downstream to upstream of the shock wave.

Abstract: A low turbulence cambered surface foil, hydrofoil or airfoil, which contains indentations located on maximum camber across which a fluid can be flowed. The indentations create turbulence in the boundary layer downstream of the indentations, changing the characteristics of the flowing fluid to a turbulent boundary layer ahead of the normal point of separation of the fluid from the foil, this causing the fluid to cling close to the surface of the foil and postpone or delay trailing edge separation of the fluid stream from the foil. The noise level is reduced, the performance and efficiency of the foil is improved, or both the noise level is reduced and the performance and efficiency of the foil is improved.

Abstract: In order to reduce the noise nuisance caused during operation by rotor blades of a rotor of a wind turbine the rear edge of each blade is irregularly formed. In particular the saw-tooth form with a top angle smaller than about 150.degree. and preferably 10.degree. is found to produce a considerable noise reduction.

Abstract: A method is described for reducing drag in airframes or airfoils. The method includes inducing cavitation in the boundary layer separating the airframe or foil skin and the air currents passing thereover to produce a reduced pressure area instead of turbulent flow. In one embodiment of this invention, a nose cone is provided for the airframe which at the juncture of its base portion provides a step between the terminal portion of the nose cone and the adjacent portion of the fuselage skin. This provides a circumferential step surrounding the fuselage which in its leeward direction induces the cavitation necessary to reduce drag. In another embodiment of this invention, steps can be provided longitudinally at mutually spaced circumferential locations extending from the front along the fuselage toward to the rear to ensure that a continuous boundary layer is provided of reduced pressure.

Abstract: A lifting body moves relative to a fluid, thereby creating a vortex field in the fluid downstream of the lifting body. The lifting body has a predetermined lift distribution along the length thereof which enhances the velocity component of the fluid flow directed outwardly from the centroid of the vortex field to reduce the strength of trailing vortices. In a preferred embodiment, the lifting body is a wing with a perturbation proximate to the tip end of the wing planform trailing edge.

Abstract: A fairing for providing vortex stabilization effects to a solid submerged in a fluid with relative movement thereof between the solid and the fluid. A cavity is provided in the fairing for retaining a captive fluid formed at the cavity by the relative movement between the solid and the fluid. The cavity prevents displacement of the captive fluid from the cavity to thereby provide vortex stabilization effects to the solid.

Abstract: A wing, or similar article of airfoil section, has a variable geometry surface for the active control of shock strength and transonic wave drag. In one embodiment, the wing has a region of distensible skin (4) aft of the line of maximum section, which extends along the span of the wing in those areas that experience drag. Pressure means (10, 20, 30) within the wing outwardly deflect the distensible region and produce a local bulge in the expansion surface. This bulge induces pre-shock compression and reduces the effect of the shock. The bulge is retracted by the natural elasticity of the skin material (which can be a conventional aluminum alloy) upon removal of the applied pressure. In another embodiment, the wing has a ramp portion (14) which is outwardly deflectable for the same purpose. The invention is applicable to supercritical and natural laminar flow wings.

Abstract: Apparatus for the interference and manipulation of vortex formation and control of fluid flow to reduce noise and increase flow stability is provided. A specific embodiment is directed to a flexible jet noise suppressor for aircraft, particularly supersonic transport. The jet noise suppressor comprises at least one flexible filament having a length that is about 3 to 10 nozzle diameters. The filament(s) trail behind the nozzle and may be let out for take-off and climb and reeled in while the aircraft is in flight or on the ground. Surprisingly, the use of a single flexible filament eliminates the well-known "screech noise" at about 3,000 Hz and reduces the screech noise by about 50 dB while further reducing the broad band noise up to 15 dB over the entire sound spectrum.

Abstract: An improved airfoil using bicambered surfaces to promote laminar flow, attached flow, reattachment of flow, delayed flow separation and to achieve high angle-of-attack performance. Bicambered surfaces introduce alternating favorable and adverse pressure gradients to achieve enhanced flow control.

Abstract: To modify a turbulent boundary layer flow over a surface to reduce its drag, a series of streamwise riblet projections is provided on the surface arranged in a pattern consisting of spaced larger height projections between which are a plurality of smaller height projections The latter inhibit turbulent eddy motions from penetrating deep into the grooves between them and so displace the turbulent motion away from the wall. The larger projections control the longitudinal vortices or streaks that are characteristic of turbulent boundary layer flow and promote energy transfer to the smaller scale secondary vortices associated with the smaller projections.

Abstract: An aft facing step situated across the span of an airfoil. A chemical or thermal deicing or running wet anti-icing device is located in or on the airfoil upstream of the step, and causes water to run back towards the step. The step suddenly reduces the thickness of the airfoil chord section, which causes a disturbance in the boundary layer across the span of the airfoil downstream of the step. The aforementioned disturbance causes runback water to form droplets and be blown clear of the airfoil surface downstream of the step, thereby preventing ice from being formed on the airfoil surface downstream of the step.

Abstract: In order to increase energy efficiency by reducing the drag experienced by bodies moving through a fluid medium, such as tractor-trailers, structure is incorporated in the rear surface or panel of the bodies. The structure is implemented with a multiplicity of cavities or a multiplicity of protruding regions. The cavities or protruding regions each comprise only a small portion of the total area of the rear surface and the depth or extension dimension, relative to the rear surface or panel, is small. In the case of a tractor-trailer, the rear surface structure permits convenient access to the interior of the vehicle and can be incorporated in either a rear door assembly or in a sliding rear panel assembly. The drag reduction benefits are achieved not only when the body is a tractor-trailer but also in the case of all types of land vehicles, water craft, aircraft, projectiles and the like which have a relatively flat rear surface.

Abstract: This invention outlines excitation means to transform the linear momentum of an underwing energized jet into rotational form in a selective manner to provide an asymmetric shear layer to increase compression wave reflection from the forward undersurface of a supersonic wing. The wing compression energy is thereby recovered into useful work as an increase in pressure on the upward reflexed wing backside. The upper surface of the shear layer is comprised of an array of vortices whose rotation is opposite to the wing circulation, providing the required angular momentum reaction. The upper wing surface is flat to avoid generation of waves and an adverse angular momentum reaction above the wing. The vortices below the wing are compressed by the underwing pressure, comprising a pressure shield to enhance the reflection.

Abstract: A wing flap assembly having a contoured upper forward surface portion of the flap being arranged to reduce adverse effects of a wake producing device, such as a landing gear or a flap track faring, positioned upstream of the slot, when the flap is in its highlift slotted position. The contoured area has a moderately greater slot gap width, and relatively sharper curvature at a nose end of the contoured flap surface portion to produce a desired pressure distribution where recovery begins at a further upstream location on the flap.

Abstract: A porous airfoil having venting cavities with contoured barrier walls, formed by a core piece, placed beneath a porous upper and lower surface area that stretches over the nominal chord of an airfoil is employed, to provide an airfoil configuration that becomes self-adaptive to very dissimilar flow conditions to thereby improve the lift and drag characteristics of the airfoil at both subcritical and supercritical conditions.

Abstract: A conformable drag reduction article is provided having a patterned surface capable of reducing drag resistance by fluid flowing thereover.

Abstract: Rearward facing microsteps (11, 12, 20, 21) are provided in a wall surface (10, 10a, 10b, 19, 19a, 19b) to reduce shear friction drag caused by wall surface bounded turbulent shear flows. Microsteps combined with phased tangential flow injection adjacent the microsteps are also described. These reduce the drag caused by eddy currents. The surface is useful in any setting where turbulent flow occurs to create eddy currents such as airplanes, boats, vehicles, conduits and the like.

Abstract: A nonsmooth surface of an object in a fluid flowstream permits a reduction of turbulent drag. The surface shape is designed to approximate a minimal surface and satisfies the equation (V.multidot..gradient.).gradient..PHI.=0, where V is the relative velocity between the fluid and the surface, .gradient..PHI. is the velocity of the strain tensor. The improved surface shape may be an array of diamond shaped elements having an airfoil like diagonal along the streamline, or it may be a series of wavelets juxtaposed to one another. The specific shape of the various types of elements to be used on the surface is selected based upon the acceleration or deceleration of the fluid at the particular position on the surface, as well as the intensity of the turbulence at that position.

Abstract: An improvement in the lift and drag characteristics of a lifting surface is achieved by attaching a serrated panel to the trailing edge of the lifting surface. The serrations may have a saw-tooth configuration, with a 60.degree. included angle between adjacent serrations. The serrations may vary in shape and size over the span-wise length of the lifting surface, and may be positioned at fixed or adjustable deflections relative to the chord of the lifting surface.

Abstract: A conformable drag reduction article is provided having a patterned surface capable of reducing drag resistance by fluid flowing thereover.

Abstract: A removable spoiler is described for reducing the rotorblade or wing lift of parked aircraft. It includes an airfoil cover with an inflatable aircell installed that is temporarily mountable to project into the airflow on the top of the rotorblade or wing. It extends for the greater portion of the lift generating surface of the rotorblade or wing to which applied.

Abstract: A conformable drag reduction article is provided having a patterned surface capable of reducing drag resistance by fluid flowing thereover.

Abstract: A method and apparatus for reducing the skin friction on objects in relative motion to a field of fluid. The areas of relative low speed motion are fixed to align with a series of ridges on the surface of the object. The areas of low speed motion aligned with the ridges are removed by suction from the turbulent boundary layer which results in a reduction of drag on the object. An alternative embodiment injects fluid into areas of relative high speed between the ridges to reduce the shear and the drag caused by it. Selective suction and injection are combined in one apparatus in a second alternative embodiment. A fourth embodiment injects a polymeric solution to reduce drag. A fifth embodiment heats the fluid in specified areas to reduce drag. A sixth embodiment uses a compliant material in specified areas of the surface in contact with flowing fluid to reduce drag.

Abstract: To modify a turbulent boundary layer flow over a surface to reduce its drag, a series of streamwise riblet projections is provided on the surface arranged in a pattern consisting of spaced large height projections between which are a plurality of smaller height projections. The latter inhibit turbulent eddy motions from penetrating deep into the grooves between them and so displace the turbulent motion away from the wall. The larger projections control the longitudinal vortices or streaks that are characteristic of turbulent boundary layer flow and promote energy transfer to the smaller scale secondary vortices associated with the smaller projections.

Abstract: In modern thin wing aircraft flow separation at high incidence may originate at the leading edge. This invention combats the problem by restricting the growth of the region of separated flow by re-energizing the boundary flow downstream of reattachment line (7). It utilizes upper surface grooves (8 and 9) extending rearwardly from the leading edge (5) of the wing. The grooves (8 and 9) have a width at opening in the range 0.05 to 1.0 percent of the aerofoil span and length in the range 1 to 20 percent of the local chord length. Spanwise flow across the grooves causes vortex formation which produces the desired effect without significant drag penalty. In swept wings the grooves are parallel to chord. In straight or forward swept wings the grooves are inclined. The wing includes several grooves each acting as a barrier to growth of flow separation until swallowed within the separated flow.

Abstract: A wall having a surface in contact with a fluid, has a surface configuration which reduces drag if there is relative movement between the surface and the fluid. The wall is made of metal or of fiber composite material in such a way that sharp edged or fine ridges and grooves between the ridges are formed as integral surface components of the wall structure for simplifying the construction, reducing the weight, and increasing the useful life of structures having such walls.

Abstract: An aerodynamic or hydrodynamic surface is provided with so-called "riblets" for reducing drag by modification of the turbulent boundary layer. The riblets comprise flow-aligned elongate projections of small height. In order to increase their effectiveness in reducing drag, just those parts of the riblets which extend above the height of the virtual surface--established by the riblets themselves due to their displacing the turbulent motion away from the real surface--exhibit an abrupt transition to a cusp-shaped profile which more effectively promotes very small scale flow-aligned vortices which drain energy from the larger drag-inducing low speed flow-aligned vortices or "streaks" in the boundary layer.

Abstract: An aerodynamic or hydrodynamic surface is provided with so-called "riblets" for reducing drag by modification of the turbulent boundary layer. The riblets comprise flow-aligned elongate projections of small height. In order to increase their effectiveness in reducing drag, just those parts of the riblets which extend above the height of the virtual surface--established by the riblets themselves due to their displacing the turbulent motion away from the real surface--exhibit an abrupt transition to a cusp-shaped profile which more effectively promotes very small scale flow-aligned vortices which drain energy from the larger drag-inducing low speed flow-aligned vortices or "streaks" in the boundary layer.

Abstract: An airfoil-shaped body has a relatively thin trailing edge with a series of alternating, adjoining, downstream extending troughs and ridges in its suction surface which form wave-like surface undulations terminating at the trailing edge. The ridges in the suction surface form corresponding troughs in the pressure surface near the trailing edge; and the troughs in the suction surface form corresponding ridges near the trailing edge of the pressure surface. The resulting airfoil-shaped body has a trailing edge with a wave-like shape. The trough and ridge construction delays or prevents two-dimensional boundary layer separation without creating an undesirable drag penalty.

Abstract: A projectile having a downstream extending surface of revolution which terminates as a blunt base has a plurality of circumferentially spaced apart U-shaped, downstream extending troughs in its surface. Each trough is essentially aligned with the direction of the bulk fluid flow adjacent the surface in the vicinity of the trough, and intersects the blunt base to form a trough outlet therein. The troughs are appropriately spaced apart, sized and configured to flow full over their entire length and to cause fluid to flow into the space immediately behind the blunt base, thereby reducing base drag on the projectile.

Abstract: Retarding of the point of transition from laminar flow to turbulent flow in aerodynamic boundary layers on the surfaces of aircraft is accomplished by radiating acoustic energy at frequencies greater than twice the critical Tollmein-Schlichting frequency into the boundary layer. The acoustic energy interferes with the formation of Tollmein-Schlichting waves, thereby increasing the incidence of laminar flow and reducing aerodynamic drag.