Thrust generation and propulsive efficiency in dolphin-like swimming propulsion.

Given growing interest in emulating dolphin morphology and kinematics to design high-performance underwater vehicles, the current research effort is dedicated to studying the hydrodynamics of dolphin-like oscillatory kinematics in forward propulsion. A computational fluid dynamics (CFD) method is used. A realistic 3-dimentional (3-D) surface model of a dolphin is made with swimming kinematics reconstructed from video recording. The oscillation of the dolphin is found to enhance the attachment of the boundary layer to the posterior body, which then leads to body drag reduction. The flapping motion of the flukes is found to generate high thrust forces in both the downstroke and the upstroke, during which vortex rings are shed to produce strong thrust jets. The downstroke jets are found to be on average stronger than the upstroke jet, which then leads to net positive lift production. The flexion of the peduncle and flukes is found to be a crucial feature of dolphin-like swimming kinematics. Dolphin-inspired swimming kinematics were created by varying the flexion angle of the peduncle and flukes, which then resulted in significant performance variation. The thrust benefits and propulsive efficiency benefits are associated with a slight decrease and slight increase of the flexion of the peduncle and flukes, respectively.