2016 Volume 37 Issue 7 Pages 32-39
The monofin swimmer uses the body to undulate waves towards the monofin, like a dolphin kick. Therefore, the vortex dynamics around a monofin must be considered to estimate the unsteady propulsive force of a monofin. The aim of this study was to elucidate the relationship between propulsive forces and the unsteady flow structure around a monofin with the different oscillating center. The experiments were carried out at the oscillating center αc = 0, -10, -20°. The oscillation was performed using a driver unit of the monofin set in a circulating water flume. To measure the three-dimensional flow fields, a stereoscopic PIV method was applied to the several plane in the downstream of the monofin. The propulsive force during one oscillating cycle at αc = 0° is largest among the three case. The strength of vortex ring and its inclination with respect to the free-stream direction is important to the propulsive force generation.