A typical volleyball consists of three sections of rectangular panels on one side, for a total of six sides (3 panels).In this study, we have placed these conventional volleyballs, a ball with dimple-shaped irregularities on the surface, which is the official ball of the 1 Volleyball European Champions League, and a hexagonal unevenness on the surface, which is the official ball of the 6 USA Volleyball League. The flight characteristics and aerodynamic characteristics were examined using the ball.

　As a result, there was a difference in the drag applied to the ball depending on the surface shape.In particular, in the 18 conventional types, there was a large difference in drag with an increase in the Reynolds number (the larger the Reynolds number, the more turbulent the flow) depending on the flight direction of the ball.Considering the various serve speeds (50-80km / h) used in volleyball, it is thought that the flight distance of the same ball will change depending on the flight direction.In the hitting robot test, it was also found that the flight trajectory changes significantly (anisotropic) when the flight direction of the ball is changed.

　On the other hand, in the newly designed volleyball, the change in drag force depending on the flight direction of the ball is relatively small, and the flight distance tends to be stable regardless of the direction of the ball.In the hitting robot test, a relatively stable flight trajectory (isotropic) was observed compared to the conventional type.

　From the above, it was found that the flight trajectory can be improved by changing the surface shape of the ball.It is expected that this knowledge can be utilized for future ball research and development and design.

Paper information:[Applied Sciences] Surface patterns for drag modification in volleyballs