Mitigation of Airfoil Gust Loads Through Pitch

Wings can experience a large increase in lift when subjected to a high-amplitude transverse gust, which may adversely affect their controllability. This study analyzes the capability of airfoil pitch motions to mitigate such lift spikes. The mitigation pitch kinematics are calculated preemptively from gust velocity measurements using two approaches. First, a simple quasi-steady model of the lift force is used to counteract the gust-induced angle of attack. Second, the classical unsteady theories of Wagner and Kussner are utilized to account for the effects of trailing-edge vorticity and noncirculatory forces. Experimental force and flow measurements are analyzed for gust ratios from 0.25 to 1.5. Results show that the motions predicted by the quasi-steady model achieve a lift peak alleviation of 70%, whereas the unsteady pitch profile results in a superior 90% alleviation. This accurate mitigation for high-amplitude gusts is analyzed by comparing the flow development with the main assumptions in the models, like small angle of attack and no shedding from the leading edge. Further analysis includes experiments where the wing experiences only the gust or only the pitch motion. Ultimately, the outcome of this work can be used to improve the control mechanisms on board of flying vehicles.