Analysis of influence of caudal fin shape of bionic sturgeon robot on propulsion efficiency

The caudal fin shape has an important influence on the propulsion performance of bionic sturgeon robot. In this paper, the upper and lower asymmetrical caudal fin model is parameterized for sturgeon robot, which is used to determine the main shape parameters including the upper leading edge angle, lower leading edge angle, trailing edge angle and depth of the caudal peduncle. A kinematic model is established for the movement of the caudal fin in space. Based on numerical simulation analysis, the influence of each shape parameter on the caudal fin propulsion performance is analyzed through the variation trends of propulsion efficiency, input power, thrust coefficient and lateral force coefficient with the change of Strouhal (St) number. The propulsion mechanism of the caudal fin is analyzed through vortex-volume, surface pressure and flow field pressure distribution cloud diagrams. It is found that the vortex structure and pressure difference generated during the movement of the caudal fin jointly form a thrust to drive the movement of the caudal fin. The variation of the lateral force of the caudal fin over time is further analyzed and verified through experiments.