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Tennis ball designs are currently being altered with a view to reducing the service speed. A tennis ball, with a diameter increased by 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. [ABSTRACT FROM AUTHOR]

Badminton is as popular as lawn tennis (when ‘popular’ is defined by the number of adults who play the game). Indeed, the origin of the game, played with a feather shuttlecock, in the mid-19th century is said to predate lawn tennis. The invention of the cheaper, more durable synthetic shuttlecock in the 1950s gave the game a wider appeal. Yet, manufacturers have still to produce a synthetic shuttlecock that exactly mirrors the flight of the feather shuttlecock during the game of badminton, a goal they have striving to reach for over 40 years. This paper describes experiments which were devised to understand the flow regime around a shuttlecock and to accurately determine a data set of aerodynamic coefficients for selected feather and synthetic shuttlecocks. The drag, lift and pitching moment coefficients were measured for a range of Reynolds Numbers (based on maximum skirt diameter) selected to cover most velocities reached in a badminton game; 13 000 < Re < 190 000 (3 to 44 m s[sup –1]). The results form part of a wider programme of research which examined the differences between feather and synthetic shuttlecocks and ultimately led to a new product. [ABSTRACT FROM AUTHOR]