Optimizing Wing Lift to Drag Ratio Enhancement with Flexible-Wall Turbulence Control

Multiple in flight sink-rate measurements of a Standard Cirrus sailplane verified 18% increase in average best glide ratio (L/D) by treating 8% of the mean aerodynamic chord of the wing upper surface with a passive Flexible Composite Surface Deturbulator tape. The periodic ridged substrate of an optimized Deturbulator mitigates turbulence producing vortices by breaking long wavelength flow induced oscillations of the flexible surface. Attenuating turbulence can be used to promote a thin nearly stagnant non-dissipative separated zone on top of the wing. When optimized this increases the effective airfoil camber while eliminating skin-friction and pressure drag. Closer examination of the sink-rate data alludes to the possibility of increasing L/D by 100% when such conditions are realized.

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