The effect of spanwise flexibility on the propulsion performance of an oscillating pectoral fin

The pectoral fin is a major source of thrust generation for fish utilizing median or paired fins (MPF) mode. Along with the pectoral fin, spanwise flexibility plays a major role in the generation of thrust. This paper investigates the effect of spanwise flexibility on propulsion performance using theoretical and experimental studies. For this study, the kinematic model of oscillating pectoral fin is first established based on the mechanism of active/passive flexible deformation. The dynamic model of the oscillating pectoral fin is developed based on the blade element theory. The influence of spanwise flexibility on propulsion performance is analyzed theoretically. Experiments have also been carried out to study the propulsion performance of the bionic pectoral fin by changing spanwise flexibility. Both calculated results and experiment results show that the propulsion performance of the bionic pectoral fin can be enhanced with the certain degree of spanwise flexibility.