The role of hydrofoil shape in rigid/flexible oscillating propulsors

The field of aerodynamics has countless libraries of foil shapes that are optimized for steady flight performance. However, it is unclear if these same foil characteristics are ideal for foils used as unsteady propulsors, as found naturally in biological swimmers and increasingly used in underwater vehicles. We detail the role that hydrofoil shape characteristics like maximum thickness and thickness distribution have in swimming speed and efficiency. Through optimization, we arrive at the ideal foil shape for a rigid foil and a foil that passively pitches through a leading edge spring. Results are primarily obtained through a boundary data immersion method flow solver and compared to experiments. Through shape optimization, we are able to dramatically increase the propulsive performance of underwater swimmers.