An Overview of Tennis Ball Aerodynamics

Abstract

Tennis ball designs are currently being altered with a view to reducing the service speed. A tennis ball, with an increased diameter of 6.5%, is currently being tested by the International Tennis Federation at major tennis tournaments. This paper considers the aerodynamics of the tennis ball and does not address ball impacts. It investigates the ball behaviour during two flow regimes: the initial, unsteady state after racket impact and the quasi-steady motion after any transient features have died away. It is concluded that the transient stage in the development of the ball's flow regime can be considered negligible, affecting at most the first 3% of its trajectory and altering the initial velocity by less than 1%. Existing drag coefficient data is considered. Cd is 0.55 for a standard tennis ball during serve with no spin (200,000 < Re < 270,000) and this is compared to drag data for spherical models with varying surface irregularities. Further work is identified.

Tennis Balls
Authors

Dr. Alison J. Cooke - Department of Engineering, Cambridge University. UK