Investigation of propulsive force and water flow around a small fish robot by PIV measurement and three-dimensional numerical analysis

Swimming velocity and propulsive efficiency of fish robots are extremely low in comparison with actual living fish. Therefore, using the sea bream as a model, a flexible fish robot was developed to study its propulsion performance. The individual effects of the shape, thickness, flexibility and moving pattern of the tail fin on the propulsive force were investigated experimentally by using Particle image velocimetry (PIV) measurements and three-dimensional computational fluid dynamics (CFD). Consequently, it was confirmed that the propulsive performance of the fish robot can be improved when vortex rings are successively formed downstream of the tail fin to form a reverse Karman vortex street.