2D-numerical simulation of flexible oscillating fin mimetic bony fishes fin

A controllable flexible biomimetic fin actuated by Shape Memory Alloy (SMA) was presented to imitate the flexible bending of fin rays in bony fishes. Based on the bending experiment of the biomimetic fin, the kinematics model was set up. Then a two-dimensional numerical simulation on the oscillatory biomimetic fin was performed by computational fluid dynamic to investigate the interaction with the surrounding fluid and the propulsive force production. By solving the 2D, incompressible, laminar, unsteady Navier-Stokes equations, the computational results show that the biomimetic fin generates a vortex ring after a complete period in still water which can generate a thrust force. The dynamics performance of the vortex ring is achieved and then the average propulsive force is calculated on different oscillatory frequencies and maximum bending angles to find the change character. At last, an important parameter, the Strouhal number was discussed in this paper. Different Wake pattern were observed depending on different velocities of the background flow, which decide the Strouhal number. When the 0.2<St<0.3, the wake shows evidence of an approximate momentum balance.