抄録
Dimples on a sphere lengthen the range greatly in comparison to a smooth surface, as well-known. The present paper described the principle of lift production from both separation and wake of a sphere by fundamentally theoretical analysis, and confirmed it from both approaches of lift measurement and flow visualization by the experiments using a wind tunnel. Drag and lift on the model sphere given back-spin were measured simultaneously, and the flow around the one was visualized and recorded by a high-speed video camera. The ballistic trajectories of dimpled spheres in back-spin were calculated referring to both coefficients of drag and lift measured experimentally, and searched for the number and depth of dimples at the maximum range. We proposed the design condition to optimize simultaneously both effects of drag reduction and stable production of positive lift by dimples on a back-spinning sphere.
