Effect of a rotating and swept wingtip on streamwise gust alleviation

Dynamic effects of wing planform changes are investigated with the goal of gust alleviation. Force measurements are done on a low-aspect-ratio high-angle-of-attack translating wing having a rectangular planform that incorporates a moving tip with in-plane rotation and sweep. To create streamwise gusts, the wing is towed in a water tank from constant motion to a new velocity that is 50% higher (“step-up”) or lower (“step-down”) through ramp distances of 1, 3, and 6 chords traveled. The tip panel is rotated inward for the step-up cases to lower the gust lift peaks and outward for step-down gusts to mitigate the lift lost. The actuation cases are compared using the unsteady C_L with two reference geometries (pre- or post-gust wing shapes). In most cases, actuation yields better gust-force change for (Formula Presented) = 2 than (Formula Presented) = 4, due to the greater change in wing planform. The actuation timing also alters the details of the force recovery. Furthermore, an impulse metric shows that inward tip actuation can mitigate the gust-impulse change by as much as 38% and outward tip actuation by 84%. A superposition of the individual effects of the actuation and gust is tested against the cases of actuation during gusts.