Aerodynamics of a cricket ball

This paper describes experiments performed on stationary and rotating cricket balls to determine the aerodynamic forces acting on the ball over a range of bowling speeds and seam angles. Lift, drag and side forces were measured directly and it was found they exhibited magnitudes in the order of 1.4, 1 and 0.4 N, respectively, for the stationary ball. At air velocities above 20 m/s, the lift force increased with increasing air speed being weakly influenced by the vertical seam angle. At 10 m/s air speed, the side force began to increase steadily with air speed for seam angles up to 70°. At 80° the side force direction reversed due to the sudden movement of the separation point on the surface of the ball. Roughening one side of the ball increased the side force but delayed its reversal at 80° seam angle until a marginally higher velocity was reached. When top spin was applied to the smooth ball, the lift force increased almost linearly in the negative direction but there was no resultant side force. When a roughened ball was spun, the negative lift force was constant at all air speeds over a range of rotational speeds. The development of the measured forces are discussed in terms of boundary layer flow and Magnus effect. © 1999 Elsevier Science Ltd. All rights reserved.