Passive Turbulance Control Product for Minimizing Drag and Its Method of Manufacture

Abstract

A method of manufacturing a surface that will reduce fluid flow drag over exposed surfaces of aerodynamic or hydrodynamic structures. The surface shall define a plurality of dimples. The dimples might not be aligned. Adjacent dimples might not have the same diameter.

Description

FIELD OF THE INVENTION

The present invention relates to the art of reducing fluid flow drag over aerodynamic or hydrodynamic surfaces, e.g. watercrafts, airplanes, automobiles, airfoils, rudders, propellers, rockets to name a few. The inventor has developed a method of placing a dimple pattern to all of the exposed surfaces that would be in contact with the fluid flow, thereby reducing the fluid flow drag. The dimple pattern would be similar to the pattern found on existing golf balls. The dimple pattern could be applied to the surfaces prefabrication or post fabrication. The dimple pattern would be stamped on to prefabricated surfaces. To existing surfaces, a dimple pattern film would be applied to the surfaces.

BACKGROUND

There is a need to reduce the drag, the combined effects of friction drag and pressure drag, felt by bodies when passing through a fluid flow. When the drag effect felt by a body is reduced, the energy necessary to have the fluid flow is decreased exponentially hence in most instances the fuel consumption is reduced. For example, it has been estimated that a one percent reduction in drag across the leading edge of a wing of one BOING 727 jet airliner would reduce the fuel consumption by more than 20,000 gallons per year. See Automotive Engineering, February, 1982, pp. 73.

Reducing the drag felt across all the exposed surfaces of a body, not just the leading edge of a wing, will also reduce fuel consumption when a body is passed through a fluid flow. For example, it is desirable to reduce the drag caused by water flowing past the hull of a boat, air flowing past a moving automobile or air flowing past the blades of a windmill fan, airfoil, fan, rotor, stator, inlet, etc. The inventor of the present invention realized that if he could provide a method of reducing the drag effect felt by all exposed surfaces of a body, that he would reduce the energy required to make the body travel through the fluid. The present invention is directed to providing a commercially viable solution for reducing the drag effect felt by all the exposed surfaces of a body when the body passes through a fluid flow.

Friction drag and pressure drag are persistent problems in aerodynamic and other types of fluid flow design. Friction drag results primarily from the force of friction between a surface such as a wing or a fuselage section and the air or other fluid found within the boundary layer adjacent to that surface. When a body passes through a laminar fluid flow, the effect of friction drag is relatively small. However, when a body passes through a turbulent fluid flow, the frictional drag force is typically greater when compared to a laminar flow. With respect to modern aircraft, the frictional drag component can account for fifty percent or more of the total drag force experienced by such aircraft. Similarly, other aerodynamic or hydrodynamic structures such as a watercraft, automobile, airfoil, rudder, propellers, rockets or the like may experience large frictional drag forces due to turbulent flow passing over their external surfaces.

A second type of drag occurs when a fluid flow passes over an aerodynamic or hydrodynamic surface, hereinafter either surface shall be referred to as “surface,” and the fluid flow separates from the surface. The separation creates low pressure pockets behind the surface. Such fluid flow separation might be caused when the surface interacts with the fluid flow at a high angle of incidence or “angle of attack.” The resulting low pressure pocket creates a retarding force and is commonly referred to as pressure drag.

An energized or turbulent flow is less likely to become separated from a surface than a non-energized or laminar flow. Thus, one method of reducing pressure drag is to artificially convert or “trip” the laminar fluid flow over the surface to a turbulent flow. The energy within the turbulent boundary layer helps to maintain the flow attached to the surface, thereby reducing or delaying flow separation until a higher angle of attack so that a reduction in the total amount of pressure drag is achieved.

Many prior methods have been used to reduce both friction and pressure drag. With respect to pressure drag, some of these methods include adding structures to the leading edge of surfaces. Such structures may include rough strips extending span wise along the leading edge of the surface or a plurality of vortex generators spaced along the leading edge. These structures extend into the relatively thin laminar boundary layer to disrupt the laminar flow, thereby prematurely tripping the flow to a turbulent state and energizing the boundary layer so that the flow is less likely to separate from the surface. While these and other similar structures may successfully reduce the pressure drag associated with flow separation, they do not address the resultant increase in friction drag caused by the larger proportion of turbulent flow within the boundary layer.

With respect to friction drag, a turbulent boundary layer has a greater velocity gradient than a laminar boundary layer, and the greater velocity gradient, combined with the inherent instability within the turbulent boundary layer, tends to transfer a relatively high amount of momentum from the boundary layer to the aerodynamic surface. Prior means for reducing friction drag have included both passive and active techniques for reducing the instability or the momentum transfer within the turbulent boundary layer. Examples of the passive control means include rivets formed on the surface and application of films and coating systems with grooves and rivets aligned in the stream wise direction of the fluid flow over the surface, the stream wise grooves formed by the rivets attempt to redirect the stream wise fluid flow within the boundary layer away from the surface, thereby reducing the momentum transfer between the boundary layer and the surface. However, while such passive devices have demonstrated that they are capable of reducing friction drag, the net effects of such devices are lessened due to offsetting drag increases in other areas. For example, while rivets may decrease the effect of friction drag, they also increase the wetted surface area of the surface so that the total amount of friction drag is not dramatically decreased. Additionally, the parameters of the rivets are not easily changed once they are optimized for a particular flight condition. The passive devices described above contribute extra form or device drag to the total drag of the surface. One example of an active form of friction drag control is a suction system in which a pattern of fine holes is formed in the aerodynamic surface. Suction is applied to the holes to create a pressure gradient that suppresses instability growth within the turbulent boundary layer. However, the obvious drawbacks of such a system include its cost, ongoing maintenance and its susceptibility to adverse weather conditions.

Many solutions have been proposed for mechanically altering fluid flow over flow control surfaces. For example, the utilization of various devices to direct air into ducts exiting the trailing edges of the flow control surfaces. See, for example, U.S. Pat. Nos. 2,742,247; 2,925,231; 3,117,751; 3,521,837; 4,114,836; 4,258,889; and 4,296,899. U.S. Pat. No. 4,434,957 suggests the use of a corrugated fluid control surface. The corrugations that extend transversely into the direction of the fluid flow temporarily retain vortices formed in the fluid flow on the flow control surface, and aid in regulating the passage of the fluid flow across the surface. U.S. Pat. No. 4,455,045 proposes the use of one or more 3-sided submerged channels in the flow control surface. Each channel includes two divergent walls that form a generally V-shaped ramp that is sloped downward so that each channel widens and deepens toward the downstream flow of the fluid flow. Such channels are V-shaped in a plane and are generally parallel to the flow control surface. The channels are intricate and are most effective when provided in a serial cascade and wherein the last channel in the cascade ends at the trailing edge of the flow control surface. The above inventions are expensive to develop, time consuming to employ and do not provide a solution for reducing the drag felt by a body's exposed surface when the body passes through a fluid flow.

The use of smooth surface coatings on airplane skins have also been suggested. See Automotive Engineering, February, 1982, pp. 73-78. The article reported that liquid polymeric coatings and adhesively backed films applied to flow control surfaces, in order to maintain a smooth and protected surface for reducing drag, performed poorly and were unsuitable for areas of high erosion such as wing and tail leading edges and nacelle inlets. U.S. Pat. Nos. 4,872,484 and 4,974,633 describe systems for affecting the fluid flow relative to an object. The patents disclose having a plurality of surface deviations disposed on the surface of an object in which the deviations are grouped into at least one set and the sets are arranged into at least one predetermined pattern. The patents do not address having the deviations covering the totality of the exposed surfaces of a body that passes through a fluid flow.

U.S. Pat. No. 5,069,403 discloses a practical technique for significantly reducing drag only across the flow control surfaces given that in general, at these surfaces, the fluid trajectory is perpendicular to the film and the patterns stated therein are aligned in the stream wise direction to the fluid flow. The invention comprises of a conformable sheet material that employs a pattern surface to reduce drag. The material is used on certain areas of aerodynamic or hydrodynamic structures. The material is not used to cover all exposed areas of a body passing through a fluid flow.

An article written in 1992 entitled “Suppression of Turbulence in Wall-Bounded Flows by High-Frequency Span Wise Oscillations,” Lung et al. utilized computational fluid dynamics simulations to determine whether a reduction in turbulence-induced drag could be realized in a simulated bounded channel flow by rapidly oscillating one of the channel walls in a span wise direction (orthogonal to the direction of the simulated free stream channel flow). The article notes that the turbulent bursting process was suppressed and significant reductions in the calculated turbulent drag force were realized. However, Lung et al. offered no explanation or suggestion of how the span wise oscillations could be achieved outside the purely computational realm. U.S. Pat. No. 5,901,928 discloses an active turbulence control technique for drag reduction that is based on the active generation of bending waves. The technique is limited in its application: applicable only to surfaces on which fluid trajectory is perpendicular to the wave oscillation generator. Because such application can only be utilized on certain areas of an aerodynamic or hydrodynamic structures such as a watercraft, airplane, automobile, airfoil, rudder, propellers, rockets or the like; therefore limiting the practical application and not significantly improving the overall performance of the structure.

An object of the present invention is to reduce drag over all exposed surfaces of a body when the body passes through a fluid flow.

Another object of the present invention is to reduce the energy required for a body to travel through a fluid flow.

Other objects of the invention will become apparent in view of the following description taken in connection with the accompanying drawings.

SUMMARY

The object of the present invention is to provide a surface that will reduce the drag and thereby reduce the energy required for a body to travel through a fluid flow by stamping an existing surface with a dimple pattern design similar to those found in golf balls or by covering the surface with a film having a similar a dimple pattern design. The present invention may be used on the following bodies: watercrafts, aircrafts, automobiles, airfoils, rudders, propellers, rockets or any other body that may be in contact with a fluid flow.

When either stamping the exposed surfaces with the dimple pattern design or when covering the exposed surfaces with the dimple pattern design film, the dimple pattern design will reduce the drag over the exposed surfaces by energizing the boundary layer between the fluid and the surface, thereby enhancing the turbulent process by disrupting the laminar flow and reducing the transfer of momentum between the turbulent flow and the surface.

DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and drawings where:

FIG. 1 illustrates a spherical square having a dimple pattern for a golf ball that is more fully described in FIG. 4 of U.S. Pat. No. 4,960,281;

FIG. 2 illustrates a spherical equilateral triangle having a dimple pattern for a golf ball that is more fully described in FIG. 4 of U.S. Pat. No. 4,960,281;

FIG. 3 illustrates another spherical square having a dimple pattern for a golf ball that is more fully described in FIG. 4 of U.S. Pat. No. 4,960,281;

FIG. 4 illustrates a preferred spherical square having a dimple pattern for a golf ball that is more fully described in FIG. 4 of U.S. Pat. No. 4,960,281;

FIG. 5 illustrates a preferred spherical square having a dimple pattern for a golf ball that is more fully described in FIG. 4 of U.S. Pat. No. 4,960,281;

FIGS. 6A-6B show cross sectional views of how fluid flow flows across sections of an airfoil, one figure uses the first embodiment of the present invention and the other does not;

FIG. 7 illustrates a perspective view of an airfoil utilizing the first embodiment of the present invention;

FIG. 8 illustrates a cross sectional view of the airfoil utilizing the first embodiment of the present invention;

FIGS. 9 and 10A illustrate a top view and greatly enlarged cross sectional view of the second embodiment of the present invention as a conformable dimple pattern film.

FIG. 10B illustrates a side view of the second embodiment of the present invention as a conformable dimple pattern film and its edge finish.

FIG. 11 illustrates a perspective view of how the second embodiment of the present invention is applied as a film layer to exposed surfaces of an aircraft's fuselage and the fluid flow lines showing non-linear flows.

FIG. 12 illustrates a perspective view of the second embodiment of the present invention applied to exposed surfaces of a commercial jet aircraft's fuselage and the fluid flow lines showing non-linear flow.

DESCRIPTION

A method of manufacturing a surface that will reduce fluid flow drag over exposed surfaces of aerodynamic or hydrodynamic structures. The surface is manufactured by providing a surface that will be used to fabricate exposed surfaces of aerodynamic or hydrodynamic structures and applying a dimple pattern design, similar to those found in golf balls, to the surface.

As shown in FIGS. 1-7, the present invention is directed to a method of manufacturing a surface that will be used to reduce fluid flow drag over exposed surfaces of aerodynamic or hydrodynamic structures. The surface is manufactured by providing a surface that will be used to fabricate exposed surfaces of aerodynamic or hydrodynamic structures and applying a dimple pattern design, similar to those found in golf balls, to the surface. The dimple pattern design is more fully described in U.S. Pat. No. 4,960,281. As shown in FIGS. 1-5, the dimple pattern designs stamped on the exposed surfaces are not linearly aligned. In a preferred embodiment, the dimple pattern designs will be composed of dimples and adjacent dimples shall have different diameters. The dimple pattern designs will be applied to exposed surfaces of aerodynamic or hydrodynamic structures that will be in contact with a fluid flow, e.g. watercrafts, aircrafts, automobiles, airfoils 4, rudders, propellers, rockets or any other body that may be in contact with a fluid flow. Methods of stamping surfaces are known in the art of stamping and shall not be described herein.

The dimple pattern designs of FIGS. 1-5 can be stamped onto curved or flat exposed surfaces. The novelty of the invention is applying the dimple pattern design to exposed surfaces of aerodynamic or hydrodynamic structures that will be in contact with fluid flows.

FIGS. 7-12 show a second embodiment of the present invention. In the second embodiment, a film defining a dimple pattern design is permanently attached to an exposed surface of aerodynamic or hydrodynamic structures. The film is a conforming film that defines a dimple pattern design that is capable of withstanding intense fluid flows. The conforming film having a dimple patterned surface comprised of a plurality of dimples. In a further embodiment of the present invention, the dimples will not be linearly aligned. In another embodiment, adjacent dimples shall have different diameters. A number of materials can be used to make the film. While the exact material used to provide the article of the invention is not critical, it is noted that certain materials may be better suited for certain environments. For example, when the surfaces are exposed to high temperatures, thermoset flexible materials might be preferable to thermoplastic materials. In water environments, water-resistant materials might be preferable to water sensitive materials.

It is foreseen that the film used in the second embodiment of the present invention may have an inherently adhesive side, the side would be permanently attached to the surfaces. Such film might be either passively adhesive or actively adhesive. In the former case, the adhesive might be activated by applying solvents, heat, pressure, or the like to the adhesive side prior to applying the film to the surface. In the latter case, such activation would not be necessary. In the event that a separate layer of adhesive is employed, the adhesive may be selected from a wide variety of materials such as heat activated adhesives, solvent (organic or inorganic) activated adhesives, or pressure sensitive adhesives. These adhesives preferably are compatible with the carrier to which they are applied and are resistant to water, oil, hydraulic fluids and the like. Furthermore, the separate adhesive layer preferably does not separate from the carrier during use. See U.S. Pat. No. 5,069,403.

An advantage of the present invention is that it reduces drag over all exposed surfaces of a body when the body passes through a fluid flow.

Another advantage of the present invention is that it reduces the energy required for a body to travel through a fluid flow.

While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.

Claims

1. A method of manufacturing a surface that will reduce fluid flow drag over exposed surfaces of aerodynamic or hydrodynamic structures comprising steps of:

providing a surface that will be used to fabricate exposed surfaces of aerodynamic or hydrodynamic structures; and

applying a dimple pattern design, similar to those found in golf balls, to the surface.

2. The method of claim 1, wherein the dimple pattern design is applied by stamping the surface with the dimple pattern design when the surfaces are manufactured.

3. The method of claim 2, wherein the dimple pattern design is composed of dimples and the dimples are not linearly aligned.

4. The method of claim 3, wherein the dimples will have different diameters when placed adjacent to each other.

5. The method of claim 1, wherein the dimple pattern design is applied to the surface by applying a conforming film, the conforming film having a dimple patterned surface comprised of a plurality of dimples.

6. The method of claim 5, wherein the dimples are not linearly aligned.

7. The method of claim 6, wherein adjacent dimples shall have different diameters.