サッカーフリーキックの秘密

抄録

The flight trajectory of a soccer ball is strongly influenced by aerodynamic characteristics such as drag and lift coefficient. These characteristics are known to depend on the air flow around the ball and the vortex structure developed by that flow. This study aims to clarify the dominant vortex structures of a spinning soccer ball using a free flight test. In this study, we found that large-scale counter-rotating vortex pairs are one of the dominant vortex structures for a spinning soccer ball. The large-scale fluctuation of the side force on the spinning ball was also determined to be smaller than that on the non-spinning ball. These findings show that the flight trajectory of the spinning ball is regular and stable, and hence a curled shot or pass can be aimed precisely from the beginning of its course.