Study on a self-propelled fish swimming in viscous fluid by a finite element method

A self-propelled fish swimming in viscous fluid is investigated by solving the incompressible Navier-Stokes equations numerically with the space-time finite element method to understand the mechanisms of aquatic animal locomotion. Two types of propulsion strategies, undulatory body and traveling wave surface (TWS), are considered. Based on the simulations, we find that by performing lateral undulation, the fish is able to move forward with a reverse von Kármán vortex street in its wake. In addition, there is no vortex street in the wake of the fish using TWS. In this case, the thrust of the fish is generated by the jets outside the boundary layer and the high pressure on the leeward side of the traveling wave. The results obtained in this paper will be of help in understanding of the propulsive performance of aquatic animal locomotion.