Abstract: The Mechanism of robotic fish under self-propelled swimming is numerical simulated for carangiform mode. The time history rules for kinematics and energetics parameters are explored by solving the dynamic process from the stationary state first and then accelerating to the steady state finally. Hydrodynamic performance, as well as the mechanics and fluid structures, is studied by changing the kinematics parameters during steady swimming. The results show that the velocity and force exhibit unsteady variations obviously during the self-propulsion. The translational and rotational acceleration are turned out due to the fact that force and torque acting on the fish are both unbalance during the accelerating process. When the flow becomes stable, the force acting on the fish is balanced and the steady swimming velocity is achieved. The effects of oscillating frequency and tail amplitude on the energetics parameters are studied in the steady state swimming. The mechanisms of the kinematics exerted on the steady state performance are revealed by extracting the three dimensional fluid structure. The findings are of great importance to the swimming mechanism obtained more reasonably as well as the development of a novel robotic fish.

Key words: Carangiform mode, Flow structure, Hydrodynamic performance, Robotic fish, Self-propulsion