Study on the hydrodynamics and kinematics of a biomimetic fin propulsor actuated by SMA wires

A flexible noiseless and high-efficient propulsor plays a prominent role in the performance of underwater vehicles. This paper presents a micro flexible caudal fin propulsor actuated by shape memory alloy (SMA) wires. To improve the responding frequency and fatigue of the SMA wires, a pair of slots is designed. So the SMA wires can be heated in the protection of silica gel layer and cool in the other status, i.e. flowing water. Then the propulsive performance of the biomimetic propulsor is evaluated through thrust measurement experiments. Note that higher undulating frequency does not mean stronger thrust force because the undulating amplitude descends along with the undulating frequency increase for this kind SMA propulsor. Further, the kinematics of the propulsor is analyzed and the corresponding equation of motion is obtained. At last, a three-dimensional numerical simulation on the biomimetic fin was conducted by CFD to investigate the interaction of the propulsor with surrounding water and the thrust production. The CFD results consist with the experimental results well, which verify the kinetic model and the numerical simulation.