Estimation of Aerodynamic Characteristics of Tennis Balls by Using an Air Pressure Ejection 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 air pressure ejection machine. Two video cameras were used to measure the aerodynamics of flight tennis balls at two positions separated horizontally by about 7.5 m. We proposed a new estimation method uniquely obtained from the position coordinates of the ball using the least squares method The balls were ejected at 42 m/s, 30 m/s, then the spin rate was about 2500 rpm. when ejected at 42 m/s, the average of C_D of entire balls is about 0.6, the average of C_L is about 0.2, when ejected at 30 m/s, the average of C_D is about 0.58 and the average of C_L is about 0.25. The drag coefficient was increased along with increasing flight speed, the lift coefficient was decreased along with increasing flight speed.