The Lift of a Translating Plate with Tip Sweep and Rotation

We conduct towing-tank experiments to study the unsteady lift force produced by a high-angle-of-attack translating wing with a tip panel that rotates inward or outward in the wing plane. The goal is to examine whether combined outboard sweep and rotation can influence the lift for two types of motions: a starting flow and positive/negative 1/2-sine streamwise gusts. This work could provide a method for drones to temporarily boost lift during high-angle-of-attack maneuvers and reduce lift perturbations from streamwise gusts. For the starting flow, our prior flow visualization indicates that early outward panel motion produces a new swept-edge vortex (SEV) and stretches the tip vortex (TV) and trailing-edge vortex outboard, which should enhance lift. For a gust-like forward surge, inward panel motion prior to the gust sheds the panel SEV and TV, and promotes main-wing leading-edge vortex shedding, which should decrease the lift as desired. To test the effect of the modified flow on the force, direct lift measurements are made via a transducer. The influence of varying the main-wing aspect ratio is also examined. The panel actuation timing compared to the starting and gust motions is shown to be important for the lift performance.