抄録
It is known that the finswimming is fast swimming style. The actual motion of a monofin is obviously unsteady. That is, the unsteady forces must also be considered to estimate the propulsive force of a monofin. The aim of this study was to elucidate the relationship between propulsive forces and unsteady flow structure of monofin with different kicking speed in the kick-up (upstroke) and kick-down (downstroke). Experiments were performed in a circulating water channel, the kick-up and kick-down motions of the monofin were operated by a drive unit using a stepping motor. The oscillating (pitching) center in the motion was set at -20° (0° being the horizontal plane) and the pitching angle was ±20°. The peak value of propulsive force during one kick stroke becomes larger with increasing down-kick speed, and the propulsive force is strongly associated with kicking speed during downstroke. Because, the strong vortex ring is generated near the monofin with increasing down-kick speed.
