Effect of trailing edge and span morphing on the performance of an optimised NACA6409 wing in ground effect

Abstract

A computational fluid dynamics (CFD) investigation was carried out on a three-dimensional NACA6409 wing in ground effect at a Reynolds number of 320,000. Using a multi-objective-SHERPA algorithm, a root angle of 4 deg angle of attack, a tip angle of 6 deg, a forward sweep, and a tip chord of 20% of the root chord produced an optimum aerodynamic efficiency across all ground clearances. Optimization showed a gain in aerodynamic efficiency of 41% at h/c = 0.05 ground clearance and a 31% gain at h/c = 0.2 compared to a rectangular planform wing. Next, fish bone active camber (FishBAC) morphing was applied to the optimized wing varying the morphing start locations along the chord at both the tip and root. A later start location produced the highest aerodynamic efficiency but increased manufacturing complexity. Extendable span morphing was also tested and was found that increasing the span from 1c to 1.5c increased the aerodynamic efficiency of the optimized wing by 27.4% at h/c = 0.1. Varying the span from 0.8c to 1.2c in ground effect had a small effect on the drag for small ground clearances; for large ground clearances, the total drag decreased as the span increased. Smaller gains were seen when the span morphing was applied to the rectangular wing. The FishBAC morphing was applied in the spanwise direction to morph the wingtip, sealing the flow beneath the wing. Also, the proportion of the morphing wingtip caused the trailing edge to be closer to the ground further enhancing ground effect.

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