抄録
Balls used on rugby and American football are like prolate spheroids rather than spheres.Those balls sometimes autolotate, more specifically tumble, during their flights. The present study is a fundamental approach to reveal aerodynamic characteristics of such a prolate spheroid in tumbling motion. Specifically speaking, the authors conduct subsonic wind-tunnel experiments, in order to investigate the effect of the depth-to-width ratio λ upon the tumbling of a simple two-dimensional rectangular-cross-section prism. And the authors carry out the flow visualisation by a smoke-wire method and the velocity measurement by a hot-wire anemometer together with a synchronised prism-angle measurement. As a result, there exist two flow modes for λ < 0.6 and λ > 0.6. Especially at λ = 0.5, we can see transition-process features between the two flow modes.
