EP0706472A1 - Carreaux electromagnetiques multiples pour la regulation d'une couche limite - Google Patents

Carreaux electromagnetiques multiples pour la regulation d'une couche limite

Info

Publication number
EP0706472A1
EP0706472A1 EP94923224A EP94923224A EP0706472A1 EP 0706472 A1 EP0706472 A1 EP 0706472A1 EP 94923224 A EP94923224 A EP 94923224A EP 94923224 A EP94923224 A EP 94923224A EP 0706472 A1 EP0706472 A1 EP 0706472A1
Authority
EP
European Patent Office
Prior art keywords
tiles
flow
boundary layer
fluid
magnetic field
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP94923224A
Other languages
German (de)
English (en)
Other versions
EP0706472A4 (fr
Inventor
Daniel M. Nosenchuck
Gary L. Brown
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BTG International Inc
Original Assignee
British Technology Group USA Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from PCT/US1993/006094 external-priority patent/WO1994010032A1/fr
Priority claimed from US08/169,599 external-priority patent/US5437421A/en
Application filed by British Technology Group USA Inc filed Critical British Technology Group USA Inc
Priority claimed from PCT/US1994/007026 external-priority patent/WO1995000391A1/fr
Publication of EP0706472A1 publication Critical patent/EP0706472A1/fr
Publication of EP0706472A4 publication Critical patent/EP0706472A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C29/00—Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01H—NEW PLANTS OR NON-TRANSGENIC PROCESSES FOR OBTAINING THEM; PLANT REPRODUCTION BY TISSUE CULTURE TECHNIQUES
    • A01H5/00—Angiosperms, i.e. flowering plants, characterised by their plant parts; Angiosperms characterised otherwise than by their botanic taxonomy
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
    • A01N63/00—Biocides, pest repellants or attractants, or plant growth regulators containing microorganisms, viruses, microbial fungi, animals or substances produced by, or obtained from, microorganisms, viruses, microbial fungi or animals, e.g. enzymes or fermentates
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2270/00—Control
    • F05D2270/01—Purpose of the control system
    • F05D2270/17—Purpose of the control system to control boundary layer
    • F05D2270/172—Purpose of the control system to control boundary layer by a plasma generator, e.g. control of ignition

Definitions

  • the present invention relates to multiple electromagnetic tiles for magnetically controlling the flow of a fluid along a wall and, more particularly, to magnetic control of the boundary layer on aerodynamic bodies (such as wings, rotors and flaps) and hydrodynamic bodies (such as submarine sails, bow- planes, stern appendages and propellers) .
  • aerodynamic bodies such as wings, rotors and flaps
  • hydrodynamic bodies such as submarine sails, bow- planes, stern appendages and propellers
  • a viscous fluid, and a body completely immersed in the fluid form a boundary layer at the body's surface when the fluid and the body move relative to each other.
  • the layer of fluid in contact with the body is essentially at rest, while in an area removed from the body, the fluid is moving at its free-stream velocity.
  • the region between the body and that area is known as a boundary layer.
  • the boundary layer is laminar at low Reynolds' numbers.
  • Re UL/p, where U is a characteristic velocity, such as the free-stream velocity, L is a characteristic dimension of the body, such as the length of a wing chord or boat hull, and v is the kinematic viscosity of the fluid.
  • Figs. 1(a) and 1(b) illustrate flow over an airfoil. It will be appreciated that the same principles apply whether the fluid is a liquid or a gas and regardless of the shape of the body.
  • the fluid stream 12 When the airfoil 10 is operating at a small angle of attack a, as shown in Fig. 1(a), the fluid stream 12, with a free-stream velocity U,,., flows smoothly over the upper surface 14 of the airfoil.
  • the downward deflection of the fluid stream by the airfoil causes an equal and opposite upward lift force to act on the airfoil.
  • the boundary layer may become turbulent, as indicated by the irregular flow 17.
  • the boundary layer is depicted in Fig. 1 as much thicker than it is in actuality.
  • the boundary layer may separate from the airfoil, which then stalls.
  • eddies and turbulence 18 develop in the boundary layer.
  • boundary layer turbulence increases viscous drag, which may create the need for additional propulsive force to be applied to the airfoil or other body, which in turn requires more fuel to be expended to maintain the speed of the airplane, submarine, propeller blade, etc., to which the airfoil is attached. Moreover, if the flow separates completely, additional pressure drag is created.
  • a turbulent boundary layer exhibits large velocity and pressure fluctuations, which induce noise.
  • Noise can be a significant problem in many environments, one example being submarine control surfaces and propeller screw blades.
  • Pressure fluctuations associated with boundary layer separation can cause vibration, which in turn causes fatigue, which can be a serious problem particularly in metal aircraft parts.
  • Figs. 2(a) to 2(c) depict boundary layer flow conditions that illustrate principles utilized in the present invention.
  • Fig. 3(a) is a planform view of a magnetic boundary layer control device with a single control region that illustrates the principles of the present invention and Fig. 3(b) is a cross-section along line B-B of Fig. 3(a).
  • Fig. 4 depicts a section of the fluid flow shown in Figs. 3 (a) and 3 (b) .
  • Fig. 5 is a qualitative plot relating to the conductivity of the fluid flow shown in Figs. 3(a) and 3(b) .
  • Fig. 6 shows a one-dimensional array of control region tiles that illustrates one embodiment of the present invention.
  • Fig. 9 shows one embodiment of a two-dimensional array of control region tiles.
  • Fig. 10(a) shows another embodiment of a two- dimensional array of control region tiles and
  • Fig. 10(b) is a cross-section along line B-B of Fig. 10(a), showing an alternate embodiment of a magnet arrangement that can be used in the present invention.
  • Fig. 11 is a conceptualized cross-sectional view of the flow conditions over an array in accordance with the present invention when the control region tiles are actuated at the critical frequency.
  • Fig. 12 is a plan view of the conceptualized flow conditions shown in Fig. 11.
  • Fig. 13 conceptually depicts approximate boundary layer velocity profiles along a prior art flat plate and along a flat plate with the flow conditions depicted in Figs. 11 and 12.
  • Fig. 14 conceptually depicts approximate boundary layer growth under the conditions shown in Fig. 13.
  • Fig. 15 is a plan view of an actual flow in a test set ⁇ up using an array similar to that shown in Figs. 10(a) and 10(b), as visualized by a fluorescent dye.
  • dA is an elemental area of the wall.
  • Equations (1) and (2) show that ⁇ w and D v du/dy at the wall increases.
  • Fig. 2(a) illustrates u(y) for a laminar boundary layer, shown as a solid line, and u(y) for a turbulent boundary layer, shown in a dotted line, for the same external conditions. It will be appreciated that du/dy at the wall is lower for a laminar boundary than for a turbulent boundary layer at the same location on the wall. Accordingly, viscous drag can be reduced if the flow in the boundary layer can be maintained laminar.
  • Fig. 2(b) illustrates the velocity profile in an unstable boundary layer.
  • the velocity of the fluid immediately adjacent the wall begins to slow down and can even approach zero. This is often an unstable condition, which leads to the replacement of the low velocity fluid near the wall by the higher energy (higher velocity) fluid in the free-stream.
  • the boundary layer thus established is generally turbulent, as illustrated in Fig. 2(c). Accordingly, du/dy at the wall is higher than it would have been if the transition to turbulent flow had not occurred.
  • Turbulence in the boundary layer has implications beyond the resulting increase in viscous drag.
  • the turbulent flow in the boundary layer creates noise because velocity fluctuations inherent in turbulent flow produce pressure fluctuations that tend to propagate into the free-stream flow.
  • the present invention can stabilize the flow in the boundary layer and thus reduce viscous drag and noise.
  • the present invention can also serve the purposes listed above, in ways described in more detail in the course of the following discussion.
  • the magnetic poles can be provided by any suitable structure.
  • the poles of one or more magnets can be placed flush with the surface 104 so as to form a part of the surface itself, and can even protrude from the surface.
  • a voltage source 105 attached across electrodes 106 and 107 generates an electric current density J, represented by arrows 109, between the two electrodes.
  • J electric current density
  • the electrodes 106 and 107 are insulated from the plate.
  • a direction of the current flow through the conductive fluid is in the direction from an anode electrode 106 to a cathode electrode 107 such that the current density can be expressed generally as a vector J parallel to the mean flow direction x of the fluid medium, although the lines of electric current have y- components proximate to the electrodes. As depicted in Fig.
  • a Lorentz force L represented by arrows 131, resulting from the interposition of the electric current and magnetic field, is expressed as J X B, the vector- or cross-product of J and B acting in a control region in a direction generally normal to and toward the wall 100, although near the edges of the control region bounded by the magnetic poles and the electrodes J may have significant x- and z-components.
  • the Lorentz force L J X B stabilizes the boundary layer by counteracting regions of positive and negative vorticity ⁇ , in accordance with the mechanism illustrated in Fig. 4.
  • Fig. 4 is a view looking downstream in the flow along the plate 100 in Figs. 3(a) and 3(b). (That is, a cross-section of the flow in the spanwise (z) direction.)
  • the fluid has a higher conductivity ⁇ ⁇ in the near-wall region than the conductivity ⁇ 2 in regions outside the near-wall region.
  • the "near-wall" region is that part of the flow in the boundary layer responsible for most of the turbulence production. In the near-wall region, viscous forces predominate over momentum forces.
  • the double line 140 denotes where the gradient of the conductivity ⁇ in the y-direction is at a maximum in the near-wall region.
  • the conditions under which the electrolyte 130 is introduced into the fluid flow are controlled so that the conductivity gradient is at a maximum at a predetermined distance from the wall, in accordance with principles discussed below.
  • the double line 140 is drawn in Fig. 4 at the distance from the wall where the conductivity gradient is at a maximum, as shown in Fig. 5.
  • This distance is typically between 10 and 30 wall units (y + ) , that is, 10 ⁇ y + ⁇ 30, although it can vary depending on the properties of a particular fluid flow.
  • a "wall unit” is a dimensionless number, usually expressed as y + , used by those skilled in the art to express distance when phenomena being measured relate to the flow conditions along a surface.
  • the vertical distance from the wall of a flat plate may be expressed as:
  • turbulence in a boundary layer is generally associated with regions of positive and negative vorticity + ⁇ and - ⁇ .
  • this vorticity is believed to be one of the mechanisms at work in the lift-up of near-wall low-momentum fluid and its replacement by higher momentum fluid from regions further from the wall, that is, the phenomenon explained previously in connection with Figs. 2(a) to 2(c). While the exact mechanism by which such an arrangement prevents this lift-up of a near-wall fluid is not completely understood, due to the as yet incomplete understanding of the feedback mechanisms that stimulate the creation of near-wall streamwise vorticity (+ ⁇ and - ⁇ ) , Fig.
  • L y is decreasing in the z-direction, to create streamwise vorticity ⁇ a in the positive direction that counteracts the vorticity - ⁇ that caused the dislocation 141a in the boundary layer.
  • L y is increasing in the z-direction, thus creating streamwise vorticity ⁇ b in a negative direction that counteracts the + ⁇ at that location.
  • the bolder vector for L y in Fig. 4 indicates a stronger force.
  • L y (which is negative because it is directed in the minus y-direction) becomes larger in the z-direction for the left-hand dislocation 141a, and smaller in the z-direction for the right-hand dislocation 141b, it creates vorticities in the opposite directions from - ⁇ and + ⁇ , respectively.
  • Fig. 4 illustrates how this arrangement is believed to counteract flow disturbances in the spanwise (z) direction. It is believed that the invention counteracts disturbances in the streamwise (x) direction in the same manner. That is, a schematic cross-section of the flow taken in the streamwise (x) direction instead of the spanwise (z) direction would look much the same as Fig. 4.
  • the force J X B can be provided in a direction normal to but directed away from the wall 100, which will result in the flow medium being pushed in a direction away from the wall surface 104. This effect can be used to disturb and destabilize the boundary layer by creating the dislocating vortices - ⁇ and + ⁇ .
  • the electrodes could be arranged so that the current flows across the mean fluid flow direction while the magnetic flux lines are along the flow direction.
  • the amount of current density and strength of the magnetic field can be varied with time to change that force.
  • an expedient manner of producing those variations in the arrangement shown in Fig. 3 is by providing a layer of different, preferably higher, conductivity fluid in the near-wall region. Accordingly, an aspect of the present invention involves the provision of such a layer. In such a case, B and J need not be varied to produce the L y variations necessary for boundary layer control, although for given desired flow effects B and J may still be varied spatially and temporally.
  • the present invention has numerous significant implications. It can reduce viscous drag by stabilizing the boundary layer and preventing transition to turbulent flow. In addition, it can inhibit velocity fluctuations in the near-wall region over a wide area of a flow surface and thereby damp and dissipate velocity fluctuations in the free-stream flow. This can significantly affect the acoustic field in the fluid surrounding the body. And by stabilizing the boundary layer and preventing transition to turbulent flow, the present invention can reduce heat transfer between the fluid and the body, which is of great potential significance in reducing the temperatures to which space vehicles are subjected upon re-entry into the Earth's atmosphere.
  • turbulent boundary layer flow enhances fluid mixing, which can have important ramifications in combustion and chemical processing applications (where two fluids may flow along opposite surfaces of a body to be mixed at the body's trailing edge). And a turbulent boundary layer is ordinarily less prone to separation than a laminar boundary layer, so that inducing turbulent boundary layer flow can delay separation.
  • preventing or inducing separation under controlled conditions can be used to create forces and moments on the body and provide directional control.
  • the present invention enables flow control over a large area while efficiently using the magnetic field and electric current density.
  • the optimum distances D e and D B for maintaining a certain percentage of the magnetic flow and current in the near-wall region can be calculated using Maxwell's equations. If that percentage is chosen as, say, 50%, then Maxwell's equations can be used to show that
  • That consideration illustrates another principle underlying the present invention, namely the provision of a plurality of separately actuatable control region tiles.
  • flow control over a large area can be provided with less magnetic flux and electric current than would be required to provide flow control for that area using a single control region.
  • Fig. 6 schematically illustrates the present invention as applied to a one-dimensional array of individual control region tiles.
  • a wall or flat plate 200 simulating a wing or control surface as in Figs. 3(a) and 3(b), is provided with a series of magnets having North poles 201a, 201b, ..., 201g, and South poles 202a, 202b, ... 202g. These magnets generate a magnetic field B with flux lines 203.
  • a plurality of electrodes 206a, 206b, 206c and 206d are spaced from each other to provide three control tiles 260a, 260b, and 260c, disposed in Fig. 6 in a one-dimensional array in the direction of fluid flow.
  • a slot 208a bleeds an electrolyte 230 into the fluid, in a fashion similar to that illustrated in Figs 3 (a) and 3 (b) .
  • Each electrode 206 is connected to wiring 207 that leads to a control circuit 250.
  • the control circuit is made from known components and is capable of selectively applying a potential across each electrode pair through wiring 207. That is, the control circuit 250 can apply a potential across any pair of electrodes 206a-206b, 206b-206c or 206c-206d in any polarity.
  • Fig. 6 shows the case where electrodes 206a and 206b are at the same potential, electrodes 206b and 206c are at potentials that make 206b an anode electrode relative to electrode 206c, and electrodes 206c and 206d are at the same potential.
  • a test rig was set up to perform a feasibility study using the device shown in Fig. 6.
  • the rig was tested in a flow channel in the test setup depicted in Fig. 7.
  • the rig, shown in Fig. 7, consisted of a plate 609 about four meters long, having components similar to those shown in Fig. 6 mounted thereon.
  • the boundary layer control device 608 consisted of seven permanent magnets 601a to 601g. The poles of each magnet were about 18 cm. apart, that is, the control region was 18 cm. wide in the spanwise direction.
  • Stainless steel (Type 304) electrodes 606a, 606b, 606c and 606d were provided approximately 8 cm. apart. They were approximately 1 cm. wide and 8 cm. long.
  • the electrode 606a was maintained at the anode voltage and the 606d was maintained at the cathode voltage.
  • the electrodes 606b and 606c were alternately switched between the anode and cathode voltages by a control unit (not shown in Fig. 7) .
  • the three control region tiles were sequentially actuated for 100 msec, each (with a duty cycle of 1/3) .
  • B z for each tile was about 160 gauss and J x for each tile was about 10 ma/cm 2 .
  • Various electrolytic substances were injected into the flow medium from a slot 604.
  • One such electrolytic substance consisted of a dilute solution of NaOH containing a fluorescing disodium fluorescein dye to obtain flow visualization in a manner discussed below.
  • the test tank shown in Fig. 7 consisted of a tank approximately 1.5 meters wide, 0.5 meters high and six meters long.
  • the test fluid 605 was set to flow at 15 cm/sec.
  • a laser was arranged to provide a thin sheet of laser energy 610 along the boundary layer at y + « 20 for activating the fluorescing dye in a thin layer along the surface of the plate to obtain visualization of the boundary layer.
  • a video recorder 607 was provided for recording the results of the experiment.
  • Fig. 8 includes three actual prints of the test rig shown in Fig. 7.
  • Fig. 8(a) shows the plate 609 with the boundary layer control device 608 in place.
  • the electrodes 606a are clearly visible.
  • Fig. 8(b) is a print the visualized flow over the plate when a turbulent spot is produced upstream and the tiles are not actuated.
  • Fig. 8(c) is a print of the visualized flow over the plate under the same conditions as in Fig. 8(b), except that the tiles have been actuated as described above.
  • the bright spots have essentially disappeared, indicating that the flow in the boundary layer has stabilized.
  • the present invention also contemplates a two- dimensional array 300 of n tiles as shown in Fig. 9.
  • Each tile has associated with it a pair of electrodes and a pair of magnetic poles provided by electromagnets.
  • the first row of tiles 360 ⁇ to 360 ln has associated with it electromagnets 301,, and 302,; the second row of tiles 360 2 , to 360 2n has associated with it electromagnets 301 2 and 302 2 ; etc.
  • the first column of tiles 360,, to 360 n has associated with it electrodes 306,, and 306, 2 ;
  • the second column of tiles 360, 2 to 360 ⁇ has associated with it electrodes 306, 2 and 306 2 ,; etc.
  • the electromagnets and electrodes associated with the tiles By suitably addressing the electromagnets and electrodes associated with the tiles, it is possible to provide a high degree of flow control over a large area.
  • the electrodes and electromagnets must be addressed in a fashion that ensures that no two tiles in close proximity are simultaneously actuated. Otherwise, the magnetic fields and electric currents would not be provided in the proper direction for flow control.
  • the adjacent electrodes in two adjoining tiles could not be made simultaneously to have different polarities, since current would then flow between such electrodes rather than along the tile surface.
  • the sixteen tiles are actuated in four sub-arrays 411, 412, 413 and 414, each having four tiles actuated at different times.
  • the tiles marked ⁇ * (referred to as "equal-phase" tiles because they are all actuated at the same time) are actuated by passing current J between electrode pairs 406 ⁇ and 406 ⁇ , 406 b , and 406 b2 , 406 c3 and 406,*, and 406 d , and 406 ⁇ .
  • the ⁇ , tiles are turned off and the equal-phase tiles designated ⁇ 2 are all actuated together; the equal-phase tiles ⁇ 3 and 4 are likewise actuated in turn.
  • all equal-phase tiles will be actuated, and the actuation time of each such tile is 25% of the total actuation time of all four tiles in a sub-array.
  • the equal-phase tiles in sub-arrays along the x-direction are actuated in the same order. That is, the equal-phase tiles are arranged similarly in sub-arrays 411 and 414 and in sub-arrays 412 and 414. However, in the spanwise (z) direction, the equal-phase tiles are shifted from their locations in the adjacent sub-array.
  • the equal-phase tiles comprise four groups of tiles and each sub-array includes a tile in one of those groups. More or fewer sub-arrays can be used for flow control depending on the flow conditions and the area over which the flow is to be controlled.
  • the size of the tiles varies depending on the freestream flow conditions. Typically, the dimensions of the sides of each tile have an order of magnitude about twice a characteristic thickness of the boundary layer on the plate.
  • the North pole of primary magnet 401 and the South pole of primary magnet 402 define the first row of control region tiles 406,, to 406, 4 .
  • the linking magnet 431 is disposed with its North pole adjacent the primary magnet 401 and the South pole of the primary magnet 402. This arrangement provides the desired magnetic flux density with less magnetic mass (that is, smaller magnets) .
  • ⁇ ,. is the free-stream velocity and d c is the distance between equal-phase tiles, as shown in Fig. 10(a) .
  • drag D In terms of the velocity profile u(y), drag D can be expressed as follows:
  • Equation 6 can be considered a measure of the "lost momentum" caused by the fluid velocity going to zero at the surface of the plate. Increasing that term increases the drag on the plate, since the "lost momentum" is manifested in a force on the plate in the x-direction. That term represents the area under the curve u(y) in Fig. 13, and it can be seen that the shaded region, which is the area under u (y) C ri . .. is smaller than the comparable area under either u(y) lam . or u(y) tu ⁇ ., meaning that at any given location on the plate the drag is reduced by operating at f crit using the arrangement shown in Fig. 10.
  • the drag is reduced even more dramatically than Fig. 13 would indicate, because it is believed the present invention inhibits boundary layer growth, as illustrated in Fig. 14.
  • the boundary layer flow achieved with the present invention, BL- rit . substantially reduces drag as compared to either flow with a laminar boundary layer, BL ⁇ , or a turbulent boundary layer, BL Wtb _.
  • the critical frequency f crit can thus be thought of as a resonant frequency, the value of which will depend on different factors and which will have minimum and maximum values for particular flow conditions and array topologies.
  • a resonant condition it may be possible to reduce the L force created in tiles further downstream. That is, once the flow is organized into patterns characteristic of the above-discusses aspect of the present invention, it may be that smaller L forces in following tiles will maintain that flow organization, which would reduce power requirements accordingly. It may also be possible to suitably actuate properly placed single control region tiles to organize and/or maintain such flow patterns.
  • Example No. 10 An array like that shown in Fig. 10 was tested in the flow channel discussed above in Example No. 1.
  • a test array with overall dimensions of about 0.3 meters in the x-direction and about 0.4 meters in the z- direction.
  • the test array had eight sub-arrays, actuated in a fashion indicated by the placement of the equal-phase tiles in Fig. 12.
  • the test array included permanent magnets generating a peak transverse flux of about 6000 gauss in the center of each tile.
  • the tiles were actuated by passing a peak current in an order of magnitude of about 100 ma/cm 2 between the pertinent electrodes.
  • the flow velocity was about 30 cm/sec.
  • the fluid was conductive, but no electrolyte was introduced to provide a conductivity gradient.
  • a dye was used for flow visualization as in Example No. 1.
  • Equal-phase tiles were actuated under varying conditions. It was found that the flow organized itself as shown in Fig. 15 when each equal-phase tile was actuated for 750 msec. For a duty cycle of 1/4 for equal-phase tiles, the critical frequency f crit. was thus 3Hz (the reciprocal of 4 x 750 msec) .
  • the bright regions extending obliquely across the plate in Fig. 15 are waves related to the rotational-flow regions depicted conceptually in Figs. 11 and 12. The measured drag was reduced from about 10 "1 N/m 2 to about 10 "2 N/m 2 , or approximately a 90% reduction.

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Abstract

On peut réguler la couche limite d'un fluide se déplaçant selon une direction moyenne d'écoulement par rapport à la surface de la paroi d'un corps, en créant dans le fluide un champ magnétique B présentant des lignes de flux s'étendant le long de la surface de la paroi, et une densité de courant électrique J traversant les lignes de flux magnétique dans le fluide de manière à former une zone de régulation. Le champ magnétique B et la densité de courant électrique J créent dans la zone de régulation une force J X B susceptible de stabiliser ou de déstabiliser l'écoulement dans la couche limite. On peut disposer une pluralité de zones de régulation de ce type en un réseau bidimensionnel (300) de carreaux régulateurs actionnés de manière périodique, régulière et commandée à une fréquence critique assurant la régulation de la couche limite sur une surface voulue.
EP94923224A 1993-06-25 1994-06-24 Carreaux electromagnetiques multiples pour la regulation d'une couche limite Withdrawn EP0706472A4 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
WOPCT/US93/06094 1993-06-25
PCT/US1993/006094 WO1994010032A1 (fr) 1992-10-26 1993-06-25 Carreaux electromagnetiques multiples utilises dans le controle de la couche limite de corps aerodynamiques
US169599 1993-12-17
US08/169,599 US5437421A (en) 1992-06-26 1993-12-17 Multiple electromagnetic tiles for boundary layer control
PCT/US1994/007026 WO1995000391A1 (fr) 1993-06-25 1994-06-24 Carreaux electromagnetiques multiples pour la regulation d'une couche limite

Publications (2)

Publication Number Publication Date
EP0706472A1 true EP0706472A1 (fr) 1996-04-17
EP0706472A4 EP0706472A4 (fr) 1998-02-25

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EP94923224A Withdrawn EP0706472A4 (fr) 1993-06-25 1994-06-24 Carreaux electromagnetiques multiples pour la regulation d'une couche limite

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EP (1) EP0706472A4 (fr)
KR (1) KR960703758A (fr)
CA (1) CA2166067A1 (fr)
SG (1) SG49125A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR931295A (fr) * 1946-07-19 1948-02-18 Procédé et dispositifs pour diminuer la résistance à l'avancement d'un solide dans un fluide
GB1106531A (en) * 1964-03-16 1968-03-20 Hawker Siddeley Aviation Ltd Improvements in or relating to the control of boundary layer conditions, at the surfaces of aerodynamic bodies, in particular over aircraft surfaces
FR2091847A1 (fr) * 1969-10-20 1971-01-21 Devlieger Maurice
DE1956760A1 (de) * 1969-11-12 1971-05-19 Dornier System Gmbh Einrichtung zur Beeinflussung der Grenzschicht eines Stroemungsmittels

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU491517A1 (ru) * 1972-03-10 1975-11-15 Предприятие П/Я Р-6397 Способ изменени подъемной силы крыла с посто нным углом атаки

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR931295A (fr) * 1946-07-19 1948-02-18 Procédé et dispositifs pour diminuer la résistance à l'avancement d'un solide dans un fluide
GB1106531A (en) * 1964-03-16 1968-03-20 Hawker Siddeley Aviation Ltd Improvements in or relating to the control of boundary layer conditions, at the surfaces of aerodynamic bodies, in particular over aircraft surfaces
FR2091847A1 (fr) * 1969-10-20 1971-01-21 Devlieger Maurice
DE1956760A1 (de) * 1969-11-12 1971-05-19 Dornier System Gmbh Einrichtung zur Beeinflussung der Grenzschicht eines Stroemungsmittels

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 7633 1976 Derwent Publications Ltd., London, GB; AN 76-H3378X XP002048826 & SU 491 517 A (SHPERLING N G) , 10 February 1976 *
See also references of WO9500391A1 *

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KR960703758A (ko) 1996-08-31
EP0706472A4 (fr) 1998-02-25

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