Application of conformal sub boundary layer vortex generators to a foil or aero/ hydrodynamic surface

Abstract

A method of improving aerodynamic performance of foils by the application of conformal, low drag vortex generators. A film of erosion protection material or other conformal material is placed on the foil to provide a medium for the incorporation of planform edge vortex generators. The form edge is shaped to achieve submerged vortex generating shapes of chevron or ogival planforms, extending primarily chordwise on the foil surface. The vortex generators promote improved boundary layer dynamics by mixing free stream flow into the boundary layer while minimising separation and fluid losses. At the trailing edge, the shape formed with the chevrons applied apex forward, acts as a vented gurney tab series and additionally as disruptors to the Von Karman Street wake, delaying sheet rollup into the tip vortice.

Description

RELATED APPLICATIONS[0001]The present application is a continuation-in-part application of U.S. provisional patent application, Ser. No. 61224481, filed Oct. 7, 2009, for ELASTOMERIC VORTEX GENERATORS, by Peter S. Ireland, included by reference herein and for which benefit of the priority date is hereby claimed.[0002]Elastomeric Vortex Generator Provisional patent, Ireland P S, of 10 Jul. 2009. (EFS ID 5676629 Application Number 61224481 Confirmation Number 2708 Title Elastomeric Vortex Generator(s) First Named Inventor Peter Stephen Ireland)FIELD OF THE INVENTION[0003]The present invention relates to the addition of low drag fully submerged conformal vortex generators to a surface in relative motion to a Newtonian fluid and, more particularly, to aeronautical and marine surfaces, blades, rotors, and appendages having a boundary layer with fluid flow across such surface.BACKGROUND OF THE INVENTION[0004]Performance of a foil or surface in a flow of fluid such as air or water is criti...

AI Technical Summary

Benefits of technology

[0016]In accordance with the present invention, there is provided a film surface being an advantageously machined polymeric or polyurethane tape element. This film is attached by a high shear strength adhesive that permits flexure of the film for conformal fitment to the substrate, being a wing, surface or foil such as a rotorblade, and allows for the removal of the film after use. The film is advantageously shaped so as to have a regular series of V shapes on both of the transverse edges of the film. This film is applied around the leading edge of the foil to result in these V shapes facing away from the leading edge towards the trailing edge. Thus the film is a method of incorporating a vortex generating profile planform, which also minimises the extent of straight transverse aft facing steps that exist when the film is attached around the leading edge of a foil. The commencement and termination of these V shapes are determined by the boundary layer characteristics of the foil that the surface is applied to, however in general will be applied in the region of 5% to 25% of the chord of the foil. The sizing of the V shapes is determined by the foil dimensions and Reynolds number, and can be optimised by numeric analysis or by parametric testing for any foil, or surface.

[0017]When applied near the leading edge of the blade or foil, as a vortex generator, the film is used to form a final polymeric layer being either a performance enhancement treatment or an erosion protection layer, with the beneficial effect of reducing drag either comparative to existing protective treatments or baseline, and or increasing lift, or lift to drag ratios by promoting spanwise vortices to be generated, assisting in reenergising the boundary layer aft of the film section. Thus, the invention both removes or minimises the causal mechanism of the aft facing step, thereby avoiding the adverse effects on lift and drag associated with such a step, and further, provides a series of conformal sub boundary layer vortex generators that enhance the boundary layer compared to a clean baseline blade configuration.

Problems solved by technology

It should be noted that in cases where a squat triangular form is produced, and the hypotenuse to adjacent angle is large, in excess of 60 degrees, then the resultant flow may actually be adversely affected such as to increase drag compared to a continuous transverse aft facing step.

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