Abstract: A new method of fluid-structure coupling in self-propelled swimming for robotic fish is proposed from revealing the bionic mechanism inherent in the bionic shape and bionic movement for fish. The fluid and structural variables are simultaneously advanced in each iteration within the sub-iteration, and thus the stability of the algorithm is increased. The fish swimming medium has been divided into three mediums, including fluid medium, structural medium and the interface medium for which the kinetic equations are established. Given the fish kinematics as an input, the fish locomotion is transferred to the fluid grid to form an incentive on the surrounding fluid. The fluid forces are obtained by solving the fluid equations and will be transferred to fish to be treated as the external forces to drive the fish to swim freely. And thus the interaction of the fish and the fluid is achieved. Finally, the validity of the proposed method is verified by using the self-propulsion examples. This method can evaluate the good and bad performance for the robotic fish swimming with different shapes and different laws of motion, and provide scientific basis to reveal bionic swimming mechanism.

Key words: bionic shape;bionic movement;fluid-structure coupling;self-propelled swimming