Estimation of Aerodynamic Characteristics of Tennis Balls by Using a Pneumatic Launcher Machine

Abstract

The aerodynamic behavior of tennis balls is very complex by the surface structures (felt length, material). We carried out the flight experiment to analyze the performance of tennis balls by a pneumatic launcher machine. Two video cameras were used to measure the aerodynamics of flight tennis balls at two positions separated horizontally by about 7.5m. We proposed a new estimation method uniquely obtained from the position coordinates of the ball using the least squares method. It was found that the tennis ball was rapidly decelerated due to air resistance and that the spin rate also declined. The aerodynamic characteristics could change during the flight. The average CD of entire balls was estimated about 0.6 in both cases launched at 110km/h and 150 km/h. The average CL was also estimated about 0.25 in both cases. Compared with the wind tunnel experiment, it was found that both CD and CL of the wind tunnel experiment tended to be higher than that of flight experiment results.