抄録
The configuration of soccer balls has closely approached a perfect round shape by not only reducing a number of panels but also by eliminating roughness of the panel joints by thermal bonding process recently. Therefore, in a non-rotating or low-rotating moving shot, a soccer ball drops and curves by the change of wake flow, which is called a knuckle ball effect. It is said that the cause of the swerving ball on no rotating shoot of the soccer ball depends on the outbreak of the vortex occurred in the wake. However, it is not grasped the timing among the vortex outbreak and the swerving of balls. In this study, the velocity fluctuation of the ball wake was measured with hot wire probe and the oscillation of the ball was measured with three components load cell. And also the asymmetric configuration of the ball panel against moving direction was investigated as a factor to bring unexpected change of the ball orbit. The results show that the position change of the tail of vortex ring affects the swerving of the balls and that the low-rotating ball changes its face against the moving direction and it produces irregular lateral force.
