Hydrodynamic experimental investigation on efficient swimming of robotic fish using self-propelled method

Efficient swimming of biologically carangiform robotic fish has been investigated by using a novel experimental method. The laboratory robotic fish model, which follows an exact replica of Saithe, is self-propelled on a servo towing system. The forward towing speed is determined by the fluid force acting on the robotic fish, as the fish undulates its body in the water. The importance of the self-propelled method, which allows for simultaneous measurement of internal and external forces on the robotic fish, has been demonstrated in the hydrodynamic experiment. The hydrodynamic result shows that the optimal efficient swimming pattern of the robotic fish is found at a parametric value where Strouhal number (St) and body wave speed δ are proximal dimensionless parameters of live undulatory swimmers, a maximum drag reduction rate of 38% is recorded, and the drag-reduction is defined as P_f /D_uU, where Pf is the pure fluid power, D_u is the rigid drag force, and U denotes the self-propelled swimming speed.