Effect of Integration Length on Pitching in Transverse Gusts

Small, unmanned vehicles, such as UAVs and MAVs, that fly at low speeds in urban environments are subject to relatively strong transverse gusts. These gusts result in the formation of a large leading edge vortex and highly unsteady loads that can be detrimental to flight stability. Previous studies have shown that pitching of a flat plate can reduce almost all (90%) of the gust-induced lift, but requires solving complex equations with prior knowledge of the gust flow field. The current study focuses on simpler methods of pitching that can perform just as well. The integration length is varied for effective angle of attack calculations and a flat plate is pitched to counteract it. The optimal integration length outperforms a Wagner-Küssner model that was modified for large-amplitude disturbances. An experimental optimization was performed by adjusting a pitch profile proportionally to its resultant lift. This optimization resulted in 95% gust mitigation at gust ratios 0.5 and 1.0. Additionally a modification to the Wagner-Küssner model is proposed to better match the optimized pitch profile and improves performance. PIV flow field results for vorticity contours, LEV circulation, as well as a force decomposition of circulatory and non-circulatory forces will be reported.