Optimizing foil shape for fish-like propulsion Part II: Computational optimization and hydrodynamics*

In collaboration with the Princeton University team on seeking the optimal foil shape for high-performance fish-like propulsion, a computational optimization frame is developed by combining a fast foil-shape generator using low dimensional shape modes obtained from thousands of airfoils and a sharp-interface immersed-boundary-method based incompressible flow solver for computing the hydrodynamic performance such as foil efficiency and thrust producing and unsteady flows at different Reynolds numbers. We start with solver validations and base-line cases using standard foil shapes. Then we take low dimensional mode coefficients as the design variables and use a parallel curve searching method to find optimal foil shapes under different cost functions. Hydrodynamic analysis is also conducted on the far-wake vortical structures and near-wake vortex formations for better understanding the thrust-producing mechanism in the best-performed swimming.