Abstract
In order to investigate the mechanism of propulsion in front crawl swimming, we measured flow around a disc-type wing. The structure of flow around the pitching and heaving wing is measured using particle image velocimetry (PIV) at Reynolds number of 1.25 × 10^4. The reduced frequency (K) is qualitatively shown to affect of the flow structure. At high reduced frequency (K=1.88), the leading edge vortex and tip vortex are formed in the wake of the wing and are shed when the circumferential velocity of wing reaches maximum. From two orthogonal views, it is possible that these vortexes are two section of a vortex ring. As a result we confirmed the earlier observation that high speed swimming cause sharp changes in direction with shedding of a ring vortex.
