Aerodynamics of a Rugby Ball

Abstract

This paper describes the aerodynamic forces on a rugby ball traveling at speeds between 5 and 15 ms−1. This range is typical of the ball speed during passing play and a range of kicking events during a game of rugby, and complements existing data for higher velocities. At the highest speeds considered here, the lift and drag coefficients are found to be compatible with previous studies at higher velocities. In contrast to these higher speed investigations, a significant variation is observed in the aerodynamic force over the range of velocities considered. Flow visualizations are also presented, indicating how the flow pattern, which is responsible for the aerodynamic forces, changes with the yaw angle of the ball. This flow and, in particular, the position of the separation points, is examined in detail. The angular position of the separation point is found to vary in a linear manner over much of the surface of the rugby ball; however, this behavior is interrupted when the separation point is close to the ‘tip’ of the ball.