A-28 ナックルエフェクト発生時に作用する空気力に関する風洞実験(FD球技)

抄録

Wind tunnel experiment has been conducted to investigate the knuckle effect of a soccer ball (Teamgeist). For the new experiment, pressure transducers were used to measure the surface pressure of a ball as well as an aerodynamic force balance to measure the drag and the side force. A tuft grid was used to visualize the flow structure in the wake region. Each of these measurements was synchronized to take the mutual correlation among the data. The surface pressures were measured at the front stagnation point, 90 deg. from the stagnation point. The correlation coefficients between the time variation data of the side force and the drag, and the surface pressure at 90 deg. and the side force were very high. The tuft visualization was capable of recording vortex shedding behind a ball in the supercritical Re region, which may be attributed to the cause of the knuckle effect.