WO1995000391A1 - Multiple electromagnetic tiles for boundary layer control - Google Patents
Multiple electromagnetic tiles for boundary layer control Download PDFInfo
- Publication number
- WO1995000391A1 WO1995000391A1 PCT/US1994/007026 US9407026W WO9500391A1 WO 1995000391 A1 WO1995000391 A1 WO 1995000391A1 US 9407026 W US9407026 W US 9407026W WO 9500391 A1 WO9500391 A1 WO 9500391A1
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- WO
- WIPO (PCT)
- Prior art keywords
- tiles
- flow
- boundary layer
- fluid
- magnetic field
- Prior art date
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
- F04D29/68—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers
- F04D29/681—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C23/00—Influencing air flow over aircraft surfaces, not otherwise provided for
- B64C23/005—Influencing air flow over aircraft surfaces, not otherwise provided for by other means not covered by groups B64C23/02 - B64C23/08, e.g. by electric charges, magnetic panels, piezoelectric elements, static charges or ultrasounds
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
- F04D29/68—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers
- F04D29/688—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for liquid pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15D—FLUID DYNAMICS, i.e. METHODS OR MEANS FOR INFLUENCING THE FLOW OF GASES OR LIQUIDS
- F15D1/00—Influencing flow of fluids
- F15D1/10—Influencing flow of fluids around bodies of solid material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C2230/00—Boundary layer controls
- B64C2230/12—Boundary layer controls by using electromagnetic tiles, fluid ionizers, static charges or plasma
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- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T50/00—Aeronautics or air transport
- Y02T50/10—Drag reduction
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.
- the tiles are disposed in a two-dimensional array and the control means periodically actuates the tiles in a predetermined pattern.
- Figs. 1(a) and 1(b) depict fluid flow around an airfoil.
- 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. 7 shows a test setup used to demonstrate the efficacy of an embodiment of the invention using a one- dimensional array of control region tiles like that shown in Fig. 6.
- Figs. 8(a) to 8(c) are plan views of the flow in the test set-up shown in Fig. 7, as visualized using a fluorescent dye.
- 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.
- FIGs. 2(a) to 2(c) illustrate generally accepted principles regarding flow conditions in a boundary layer, an understanding of which principles will aid comprehension of the present invention.
- the wall shear stress is related to viscous drag as follows:
- 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.
- Fig. 3(a) is a planform view of a device illustrating principles underlying the present invention.
- a wall or flat plate 100 simulating a wing or a control surface, is provided with a magnet having a North pole 101 and a South pole 102 for generating a magnetic field B with flux lines 103.
- the flux lines 103 enter and exit the surface 104 of the wall, thus being generally oriented parallel to the wall surface 104 and normal to the free-stream fluid flow direction x, although they have y-components proximate to the magnets.
- the coordinate system used herein is shown in Figs. 3(a) and 3(b) .
- the magnetic poles 101 and 102 shown in Fig. 3(a) are provided by a horseshoe magnet (not shown) beneath the plate 100 (that is, on the side opposite the surface 104) , and the plate is a non-ferrous material that allows free passage of magnetic flux.
- An electromagnet can also be used.
- 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.
- an electrolyte 130 is added to the boundary layer by bleeding an electrolyte from a reservoir 108 through a slit 108a into the medium to increase the conductivity of a thin layer of the liquid adjacent to the wall.
- 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.
- Controlling boundary layer separation is, of course, important because of both the form (pressure) drag and the unstable pressure fluctuations associated with such a flow condition. Separation greatly increases the drag on the body due to the altered distribution of pressure when the flow separates. Accordingly, preventing separation reduces such drag. Separation can also create a fluctuating pressure field in the fluid that subjects the body to coupled forces which can cause fatigue. Delaying separation (by inducing turbulent boundary layer flow) or inhibiting separation (by providing a strong J X B force toward the body) , can reduce these pressure fluctuations and the resulting fatigue.
- preventing or inducing separation under controlled conditions can be used to create forces and moments on the body and provide directional control.
- One aspect of the present invention uses those principles to provide efficient boundary layer control over a wide area.
- 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.
- a microcomputer COM can be programmed to provide an appropriate addressing sequence depending on flow conditions such as free stream velocity, fluid density, angle of attack (if the array 300 is on a lifting body such as an aircraft wing or submarine control surface) , etc.
- the present invention thus enables flow control over a large area, and may reduce the strength of the magnetic field and the electric current required for the same area if only one control region were provided for such area. It also more readily enables flow control without providing a conductivity gradient in the fluid.
- Fig. 10 shows another embodiment of the invention that demonstrates flow control using a two-dimensional array of control region tiles.
- the array is formed by a series of spaced-apart permanent magnets 401, 402, 403, 404 and 405.
- the poles are arranged as alternate North and South poles, as indicated by the designations "N" and "S” in Fig. 10, and provide magnetic fields indicated by the flux lines B.
- Sixteen control region tiles 406,,, 4 0 6 i 2 - 4 °6 . _./ • • - > 406 43 , 406 ⁇ are formed by separately actuatable electrodes 406 a ,, 406 ⁇ , 406 ⁇ , 406 a4 , 406 ⁇ , 406 M , 406 b2 , . . ., 406 ⁇ , 406 d4 , 406 ⁇ .
- 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.
- each group of single-phase tiles is chosen to provide a fully closed electrical circuit at each actuated tile. That is, it is preferable that there be no electrical current between actuated tiles in different sub-arrays; for example, it is believed that the topology shown in Fig. 10(a) effectively prevents current from flowing between electrodes bounding different ⁇ , tiles when all of the ⁇ , tiles are actuated. The same is true for the ⁇ 2 , ⁇ 3 and ⁇ 4 equal- phase tiles.
- Those skilled in the art will be able to construct different topologies, using different numbers of control region tiles in each sub-array and/or different actuation patterns. Such modifications are intended to be within the scope of the present invention.
- Fig. 10(a) shows the ⁇ , tiles actuated, the y component of the resulting L (J X B) force being downward. This is true for all tiles. That is, when the ⁇ 2 tiles are actuated, the electrodes 406.,, 406 ⁇ , 406 b3 , 406, ⁇ , etc., are connected to potentials that make the current flow between electrode pairs (406 a , and 406 ⁇ , 406 bl and 406 b2 , etc.) in a direction to create an L force generally into the surface of the thus-defined control region. This control of the electrodes' potentials over time is provided by circuitry easily constructed by one skilled in the art. Fig.
- FIG. 10(b) shows the arrangement of the magnets beneath the plate 400 (omitted from Fig. 10(a) for clarity).
- This embodiment uses an alternate arrangement of the magnets, which has been found to improve the flow control provided by the present invention.
- the primary magnets 401, 402, 403, 404 and 405 are arranged as shown to provide the North and South poles that define control region tiles as shown in Fig. 10(a).
- Linking magnets 431, 432, 433 and 434 are coexistensive in the z-direction with the primary magnets 401 to 405. They are arranged with their North and South poles corresponding to the North and South poles of the adjacent primary magnets that define the control region tiles.
- 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) .
- Figs. 11 and 12 conceptually illustrate flow phenomena believed to cause the dramatic decrease in viscous drag experienced by a flat plate equipped with an array of control region tiles arranged in accordance with the present invention and actuated at f crit .
- Figs. 13 and 14 the lines marked u(y) bm and u(y) mrb. duplicate the plot in Fig. 2(a).
- the line marked u(y) crit is believed to represent a possible configuration of the velocity profile in the boundary layer formed in the flow illustrated conceptually in Figs. 11 and 12.
- the fluid velocity in the boundary layer under those conditions increases generally linearly because it can be thought of as being organized into the regions R shown in Fig. 11, and the fluid flow in such a region will vary generally linearly from the center of the region, as will be appreciated by those skilled in the art.
- 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.
- magnetic boundary layer control devices such as discussed above could be provided on any surface upon which it is desired to control the boundary layer, either to prevent or cause separation, or to remove or induce instability.
- the present invention provides a device that is simple to manufacture as discrete elements and which could be easily retrofit to craft presently in operation. Accordingly, the magnetic boundary layer control devices could be easily manufactured in large volume and delivered to a site of operation of the craft upon which it is to be installed. The devices could be easily fitted on the inside skin of the craft, for example on a submarine sail, with a minimum amount of time and effort.
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU73157/94A AU687424B2 (en) | 1993-06-25 | 1994-06-24 | Multiple electromagnetic tiles for boundary layer control |
CA002166067A CA2166067A1 (en) | 1993-06-25 | 1994-06-24 | Multiple electromagnetic tiles for boundary layer control |
JP7503059A JPH08512119A (en) | 1993-06-25 | 1994-06-24 | Multi-electromagnetic tile for boundary layer control |
EP94923224A EP0706472A4 (en) | 1993-06-25 | 1994-06-24 | Multiple electromagnetic tiles for boundary layer control |
KR1019960700274A KR960703758A (en) | 1993-06-25 | 1996-01-01 | Composite electromagnetic tiles for boundary layer control |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
USPCT/US93/06094 | 1993-06-25 | ||
PCT/US1993/006094 WO1994010032A1 (en) | 1992-10-26 | 1993-06-25 | Multiple electromagnetic tiles for boundary layer control |
US08/169,599 US5437421A (en) | 1992-06-26 | 1993-12-17 | Multiple electromagnetic tiles for boundary layer control |
US08/169,599 | 1993-12-17 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO1995000391A1 true WO1995000391A1 (en) | 1995-01-05 |
WO1995000391B1 WO1995000391B1 (en) | 1995-02-09 |
Family
ID=26786836
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1994/007026 WO1995000391A1 (en) | 1993-06-25 | 1994-06-24 | Multiple electromagnetic tiles for boundary layer control |
Country Status (3)
Country | Link |
---|---|
JP (1) | JPH08512119A (en) |
AU (1) | AU687424B2 (en) |
WO (1) | WO1995000391A1 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR20000004695A (en) * | 1998-06-30 | 2000-01-25 | 이해규 | Resistance reducing appratus of ship using electromagnetic force generating device |
CN109398655A (en) * | 2018-11-16 | 2019-03-01 | 湖南工程学院 | A kind of band verts the underwater robot of function |
FR3092818A1 (en) * | 2019-02-14 | 2020-08-21 | Airbus Operations | Aerodynamic element provided with a transverse air flow control system |
FR3118940A1 (en) * | 2021-01-21 | 2022-07-22 | Seair | Assistant motorized boat steering system by controlling foils with magneto-electric sheets. |
Citations (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1031925A (en) * | 1951-01-31 | 1953-06-29 | Method and device for influencing the flow of a fluid along a surface, for example a wing surface | |
US2946541A (en) * | 1955-04-11 | 1960-07-26 | John R Boyd | Airfoil fluid flow control system |
US3162398A (en) * | 1959-01-26 | 1964-12-22 | Space Technology Lab Inc | Magnetohydrodynamic control systems |
US3224375A (en) * | 1962-10-11 | 1965-12-21 | Hoff Marc | Apparatus for establishing plasma boundary surfaces |
US3360220A (en) * | 1959-01-26 | 1967-12-26 | Space Technology Lab Inc | Magnetohydrodynamic method and apparatus |
US3390693A (en) * | 1965-06-28 | 1968-07-02 | Electro Optical Systems Inc | Pure fluid amplifier |
US3494369A (en) * | 1965-12-21 | 1970-02-10 | Inoue K | Electric fluidic system |
US3662554A (en) * | 1970-02-19 | 1972-05-16 | Axel De Broqueville | Electromagnetic propulsion device for use in the forward part of a moving body |
US3851195A (en) * | 1972-05-26 | 1974-11-26 | Us Navy | Boundary layer control as a means of increasing power output of supersonic mhd generators |
US3880192A (en) * | 1972-07-17 | 1975-04-29 | Anatoly Alexeevich Denizov | Varying the hydraulic resistance in a pressure pipe |
US4171707A (en) * | 1977-04-25 | 1979-10-23 | Ben-Gurion University Of The Negev, Research And Development Authority | Method and apparatus for controlling the flow of liquid metal |
US4516747A (en) * | 1982-08-03 | 1985-05-14 | Messerschmitt-Bolkow-Blohm Gmbh | Method of and apparatus for controlling the boundary layer flow over the surface of a body |
US5040560A (en) * | 1990-12-05 | 1991-08-20 | Ari Glezer | Method and apparatus for controlled modification of fluid flow |
US5052491A (en) * | 1989-12-22 | 1991-10-01 | Mecca Incorporated Of Wyoming | Oil tool and method for controlling paraffin deposits in oil flow lines and downhole strings |
US5074324A (en) * | 1991-07-12 | 1991-12-24 | The United States Of America As Represented By The Secretary Of The Navy | Method and apparatus for reducing drag and noise associated with fluid flow in a conduit |
US5320309A (en) * | 1992-06-26 | 1994-06-14 | British Technology Group Usa, Inc. | Electromagnetic device and method for boundary layer control |
-
1994
- 1994-06-24 JP JP7503059A patent/JPH08512119A/en active Pending
- 1994-06-24 AU AU73157/94A patent/AU687424B2/en not_active Ceased
- 1994-06-24 WO PCT/US1994/007026 patent/WO1995000391A1/en not_active Application Discontinuation
Patent Citations (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1031925A (en) * | 1951-01-31 | 1953-06-29 | Method and device for influencing the flow of a fluid along a surface, for example a wing surface | |
US2946541A (en) * | 1955-04-11 | 1960-07-26 | John R Boyd | Airfoil fluid flow control system |
US3162398A (en) * | 1959-01-26 | 1964-12-22 | Space Technology Lab Inc | Magnetohydrodynamic control systems |
US3360220A (en) * | 1959-01-26 | 1967-12-26 | Space Technology Lab Inc | Magnetohydrodynamic method and apparatus |
US3224375A (en) * | 1962-10-11 | 1965-12-21 | Hoff Marc | Apparatus for establishing plasma boundary surfaces |
US3390693A (en) * | 1965-06-28 | 1968-07-02 | Electro Optical Systems Inc | Pure fluid amplifier |
US3494369A (en) * | 1965-12-21 | 1970-02-10 | Inoue K | Electric fluidic system |
US3662554A (en) * | 1970-02-19 | 1972-05-16 | Axel De Broqueville | Electromagnetic propulsion device for use in the forward part of a moving body |
US3851195A (en) * | 1972-05-26 | 1974-11-26 | Us Navy | Boundary layer control as a means of increasing power output of supersonic mhd generators |
US3880192A (en) * | 1972-07-17 | 1975-04-29 | Anatoly Alexeevich Denizov | Varying the hydraulic resistance in a pressure pipe |
US4171707A (en) * | 1977-04-25 | 1979-10-23 | Ben-Gurion University Of The Negev, Research And Development Authority | Method and apparatus for controlling the flow of liquid metal |
US4516747A (en) * | 1982-08-03 | 1985-05-14 | Messerschmitt-Bolkow-Blohm Gmbh | Method of and apparatus for controlling the boundary layer flow over the surface of a body |
US5052491A (en) * | 1989-12-22 | 1991-10-01 | Mecca Incorporated Of Wyoming | Oil tool and method for controlling paraffin deposits in oil flow lines and downhole strings |
US5040560A (en) * | 1990-12-05 | 1991-08-20 | Ari Glezer | Method and apparatus for controlled modification of fluid flow |
US5074324A (en) * | 1991-07-12 | 1991-12-24 | The United States Of America As Represented By The Secretary Of The Navy | Method and apparatus for reducing drag and noise associated with fluid flow in a conduit |
US5320309A (en) * | 1992-06-26 | 1994-06-14 | British Technology Group Usa, Inc. | Electromagnetic device and method for boundary layer control |
Non-Patent Citations (1)
Title |
---|
See also references of EP0706472A4 * |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR20000004695A (en) * | 1998-06-30 | 2000-01-25 | 이해규 | Resistance reducing appratus of ship using electromagnetic force generating device |
CN109398655A (en) * | 2018-11-16 | 2019-03-01 | 湖南工程学院 | A kind of band verts the underwater robot of function |
CN109398655B (en) * | 2018-11-16 | 2023-09-08 | 湖南工程学院 | Underwater robot with tilting function |
FR3092818A1 (en) * | 2019-02-14 | 2020-08-21 | Airbus Operations | Aerodynamic element provided with a transverse air flow control system |
FR3118940A1 (en) * | 2021-01-21 | 2022-07-22 | Seair | Assistant motorized boat steering system by controlling foils with magneto-electric sheets. |
WO2022156958A1 (en) * | 2021-01-21 | 2022-07-28 | Sas Seair | Assistance system for piloting a motorized watercraft by controlling foils with magneto-electric layers |
Also Published As
Publication number | Publication date |
---|---|
AU687424B2 (en) | 1998-02-26 |
AU7315794A (en) | 1995-01-17 |
JPH08512119A (en) | 1996-12-17 |
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