Aeronautics and astronautics – Aircraft sustentation – Sustaining airfoils
Reexamination Certificate
2002-07-03
2003-09-23
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft sustentation
Sustaining airfoils
C244S207000
Reexamination Certificate
active
06622973
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to aerodynamic, flight dynamics, and hydrodynamic devices, and more specifically to an airfoil or hydrofoil having independently movable surfaces on each side or surface thereof and incorporating selective fluid flow means through the surface(s), i.e., suction or “blown” surfaces. The present invention is adaptable to various devices in the field of aerospace engineering as well as in the marine environment. Hence, the term “plane” as used throughout the present disclosure, refers to a generally planar lifting or control surface (e.g., wing, fin, etc.) for dynamic operation in a fluid, and is adaptable for use in any practicable fluid, including gases such as air and liquids such as water.
2. Description of the Related Art
The development of aviation and the maritime industries has led to ever more efficient shapes and configurations for aerospace craft and marine vessels. Numerous advances have occurred over the years, including laminar flow shapes, leading and trailing edge devices for airfoils, etc. However, all such surfaces or planes rely upon the principle of differential pressure upon opposite surfaces of the plane in order to develop a lifting or turning force, depending upon their orientation and function.
The differential pressure is developed by moving a fluid over one surface of the plane at a greater velocity than the fluid moving over the opposite surface of the plane. Bernoulli explained this principle in the eighteenth century, developing the mathematical concept that pressure varies inversely according to the square of the fluid velocity over a given surface. Accordingly, most surfaces which are intended to provide a generally constant force in a predetermined direction (e.g., aircraft wings) are configured with a greater curvature over one side thereof than the opposite side, and/or operate at a positive angle of attack to develop the desired pressure differential.
Later, others recognized other means of providing such differential pressure by mechanically accelerating the fluid flow over one side of the surface. Aircraft have been developed using “blown surfaces” or “blown flaps,” in which jet exhaust is expelled over the upper surface of a wing to increase the velocity of the flow over that area and generate relatively greater lifting force. Other devices have been developed for entraining the fluid flow adjacent to the surface of the plane, by moving the surface to reduce the velocity differential between the surface and the fluid stream. This reduces the drag of the surface upon the fluid to provide a greater fluid velocity, or may accelerate the fluid to a velocity greater than that of the surface through the fluid, to provide a greater differential in velocity between the plane and the fluid for greater lifting force. Such devices are described further below.
As the sciences of aerodynamic and hydrodynamic engineering developed, the problem of control of the boundary layer of fluid immediately adjacent the surface became apparent. It was recognized as early as the 1930s that significant improvements in performance could be achieved, if some means were found to prevent the boundary layer from becoming turbulent immediately adjacent the surface, and/or to eliminate or minimize such turbulence when it occurred. “Laminar” airfoils and other shapes were created as a result, with these surfaces and shapes serving to delay, but not eliminate, the onset of turbulent flow.
Still later, it was recognized that providing some means of drawing the turbulent layer of fluid immediately adjacent the surface, into the surface (i.e., suction), served to prolong the laminar flow of fluid over the surface and thus improve performance of the craft. In some instances, applying fluid to the exterior of the surface can serve to enhance performance as well, as by “tripping” the boundary layer ahead of the normal transition point to preclude excessive turbulence at the transition from laminar to turbulent flow.
However, none of the devices known to the present inventors provides an independently movable surface on each side of a two surface plane, as well as means for inducing fluid flow through the surface (either suction or blowing), as provided by the present invention. The present invention provides a significant improvement over the prior art, by providing independently movable surfaces upon both sides of the plane and means for producing fluid flow through the movable surfaces. Thus, fluid flow may be accelerated across one surface by moving the surface in the direction of flow (opposite the direction of travel), while retarding flow over the opposite surface by moving the surface against the direction of flow (in the direction of travel). This provides a greater differential in fluid velocity over the two surfaces, thereby increasing the pressure differential between the surfaces to provide greater differential forces between the sides than are attainable with prior art devices, to improve lift, reduce drag, and improve the lift to drag ratio (aerodynamic performance). Also, moving the lower surface in the direction of flow reduces drag by reducing shear stress on the surface. The provision of blown or suction flow through the movable surfaces provides additional benefits in the control of the boundary layer immediately adjacent to the surface.
The present invention may also provide a delay in flow separation over one or both surfaces of the plane, by providing a predetermined velocity differential between the moving surface and the relative flow. By adjusting the velocity of the two independent moving surfaces of the present invention, a delay in separation may be achieved by adding momentum to the boundary layer over the upper surface, particularly at higher angles of attack. The provision for blowing or drawing fluid through the surface, provides further benefits in control of the separation of the fluid over and around the surface(s).
A discussion of the related art of which the present inventors are aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 1,674,169 issued on Jun. 19, 1928 to Anton Flettner, titled “Arrangement For Exchanging Energy Between A Current And A Body Therein,” describes a series of embodiments generally employing cylinders to develop a Magnus effect or force. In some embodiments multiple cylinders are used, while in other embodiments at least a forward and a rearward cylinder are employed with a movable surface extending around the cylinders. None of the embodiments disclosed by Flettner provides independently movable surfaces on each side of the airfoil or hydrofoil, which independent dual surfaces are a part of the present invention. In addition, Flettner does not disclose any means for causing a fluid to flow through his movable (or stationary) surfaces, which fluid flow through the surface(s) is a part of the present invention.
U.S. Pat. No. 1,785,300 issued on Dec. 16, 1930 to Filiberto de la Tour Castelcicala, titled “Rolling Apron For Airplane Wings,” describes an airfoil having a series of endless flexible belts which wrap about both the upper and lower surface and around the leading and trailing edge of the wing. Drive rollers are provided at the leading and trailing edges, with pinions engaging toothed bands disposed along the inner surfaces of the belts. The upper and lower surfaces of the de la Tour Castelcicala wing are interdependent, with the velocity of one surface determining the velocity of the opposite surface. If the upper surface of the de la Tour Castelcicala wing is traveling forwardly relative to the wing structure, then the lower surface must travel rearwardly. The planes of the present invention, with their two independently moving opposite surfaces, overcomes this deficiency. Moreover, de la Tour Castelcicala did not provide any actuation or control means for his movable surface, nor did he specify any direction of surface movement for optimum effect. It is also noted that
Al-Garni Ahmed Z.
Al-Qutub Amro M.
Barefoot Galen L.
King Fahd University of Petroleum and Minerals
Litman Richard C.
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