Effect of Different Oscillating Center on Propulsive Force during Monofin Oscillation

モノフィン振動時の中心角の違いが推進力に与える影響 羽二生 稔大 1),長谷川 裕晃 2),高木 英樹 3) Effect of Different Oscillating Center on Propulsive Force during Monofin Oscillation Toshihiro HANIU, Hiroaki HASEGAWA and Hideki TAKAGI ABSTRACT 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.