Design and Hydrodynamic Characteristics of a Bionic Flexible Pectoral Fin

In order to develop a high-performance bionic pectoral fin, a bionic flexible pectoral fin based on a swing mechanism was designed with cownose ray as a bionic prototype. Meanwhile, a prototype of cownose ray was made and a hydrodynamic performance test platform was built. In this paper, the effects of stiffness, time asymmetry coefficient and space asymmetry coefficient on the hydrodynamic performance of a bionic pectoral fin were studied. The results show that, the bionic pectoral fin can do spanwise and chordwise coupled movement according to the predetermined rules. As the thickness of the bionic pectoral fin increases, the thrust increases first and then decreases. Under the condition of high frequency flapping, the thicker the bionic pectoral fin, the greater the pitching moment of the prototype, and the worse the swimming stability of the prototype. Under the condition of time asymmetry flapping, the thrust of the bionic pectoral fin can be increased by flapping up quickly and down slowly. When the time asymmetry coefficient is between 0.5 and 0.6, the pitching moment coefficient is the smallest. Under the condition of space asymmetry flapping, the thrust can be improved by locating the middle plane of the pectoral fin above the center plane. The obtained results can provide references for the efficient propulsion and high stability control of bionic pectoral fin underwater robots.