Method and device for altering the separation characteristics of air-flow over an aerodynamic surface via intermittent suction

Abstract

Active flow control devices and methods are disclosed for improving the aerodynamic efficiency of airfoils. The devices and methods pertain to applying intermittent suction or intake of low-energy boundary layer fluid into airfoils in a manner delaying or eliminating boundary layer separation.

Description

BACKGROUND OF THE INVENTION [0001] The aerodynamic performance, hence efficiency, of an airfoil, such as a rotor blade, wing, turbine / compressor blade, or windmill blade, is strongly dependent on the ratio of the lift-to-drag (L / D ratio) forces generated by the airfoil. To this end, active flow control (AFC) techniques have been utilized to increase the L / D ratio of such airfoils. These AFC techniques include providing ports and / or openings through the surface of such airfoils and applying steady blowing, steady suction, or alternating blowing and suction of fluid therefrom. Such AFC techniques have proven to be effective in increasing the lift coefficient of an airfoil, decreasing the drag coefficient, or both in a manner increasing the overall L / D ratio of the airfoil, and thereby increasing the airfoil's aerodynamic efficiency. [0002] AFC techniques are particularly advantageous in situations where large flow separations over airfoils would otherwise exist. Such situations are co...

AI Technical Summary

Benefits of technology

[0003] The present invention pertains to an AFC technique of applying intermittent suction or intake of fluid through the exterior surface of an airfoil in a manner reducing or delaying flow separation over the airfoil. This technique requires less power than is required with constant suction or constant blowing AFC techniques and provides for a greater reduction in drag as compared to oscillating suction / expulsion AFC methods.

Problems solved by technology

As is the case with the deployment of virtually all types of aerodynamic control surfaces, a drag penalty is usually incurred as a result of the deflection of a trailing edge flap system (be it a simple hinged plain flap or a more complex multiple-element slotted flap such as a Fowler flap).

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