) of the South African Institution of Mechanical Engineering

A Sayerso, N Lelimob, Anthony Sayers, Za
2007 unpublished
The flight of a cricket ball after leaving the hand of a bowler is, for given atmospheric conditions, principally governed by the speed of the ball, the angle of the seam to the direction of flight, any rotational spin applied to the ball, and the state of its outer surface with regard to the degree of wear and roughness. This paper desuibes the design of a wind tunnel test rig to accurately measure the net W, drag and side (swing) forces on stationary and spinning cricket balls. The
more » ... lls. The measurements were performed on new unused balls and arfficially roughened balls at wind tunnel air velocities between 6 and 40 mls (2.7 x 104< Re < 7.8 x 10s), and seam angles between 0 and 90o. The spin speed range was between 2 and 8 revolutions per second (rps). From the basic data, aerodynamic W, drag and side force cofficients are presented and display anomalies to account for the behaviour of the ball during play. It/umerous critical Reynolds numbers are shown to exist where discontinuities in W and side force occur, Additional Nomenclature Roman C d drag coefficient {= Dl (0.5 pnU t d' l+17 C t lift coefficient { = Ll(0.5 ptc(J2 d2 l4)} C, side force coefficient {= S/(0.5pnUtd'147y
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