LAUSR

Abstract We performed a parametric experimental study to quantify the effects of structural properties and kinematic parameters on the propulsive performance of a low-aspect ratio oscillating-foil at a chord-based Reynolds number of 80,000. Multiple foils of the same shape but varied construction allowed explicit comparison of the effect of stiffness and inertia. Forces exerted on the foil were directly measured using a load cell and decomposed into thrust and efficiency values. Quantitative patterns of phase-averaged flow velocity and out-of-plane vorticity in the near-wake of the foil were obtained using particle image velocimetry (PIV). Flexibility was shown to improve the thrust generation and efficiency of the oscillating-foils in comparison to a rigid foil baseline, particularly in heave-only kinematics. The angle of the trailing edge of the foils with respect to the direction of the incident flow was observed to have the highest influence on thrust production, and the thrust results were insensitive to whether this was achieved by passive deformation of the foil or through a prescribed pitching motion.