THE AERODYNAMICS OF STATIONARY AND SPINNING CRICKET BALLS

Abstract

There is much experimental data describing the aerodynamics characteristics of smooth and rough spheres. The non-isotropy of the cricket ball due to its special surface characteristics render all that data unsuitable for the prediction of aerodynamic forces on the cricket balls. Many previous studies on cricket balls in free flight have used indirect measurement techniques involving such as propelling the ball through air or dropping or rolling down the ball into the test section of the wind tunnel to measure the aerodynamic forces. A potential problem with these techniques is that the measured deflection of the ball, is prone to a finite error, the calculated forces being highly sensitive to the accuracy of the sampled data. Large variations in the force calculations have thus been observed which increases the uncertainty of the results. Other studies have measured aerodynamic forces with force balance using similarity considerations on simulated cricket balls. The design of the seam, outer cover material and surface finish preparation is unique to cricket balls, even slight variations could lead to large errors in force measurements so simulating or modeling a cricket ball accurately enough is complicated. This paper describes the design of a balance to accurately measure the drag on a cricket ball in a wind tunnel. The drag data presented represents a further step in understanding the aerodynamics of cricket balls by measuring the drag directly and explaining how it is governed by the speed of the ball, the angle of the seam to the direction of the flight, the state of its outer surface, and any spin imparted in terms of aerodynamic and fluid dynamics principles.