Factors affecting cricket ball swing

The basic principles behind cricket ball swing have been understood by scientists for years1–3; however, there has been only one published account of experiments on cricket ball swing4. Through a combination of flow visualization and measurements of surface pressures on a cricket ball, the individual parameters responsible for producing swing have been investigated. An accurate correlation between swing, seam angle, spin rate and flow speed was obtained in the more realistic projection tests where spinning cricket balls were projected into a wind tunnel5. For a ball to swing well, it should be released at a speed of between 15 and 30 m s−1 with the seam inclined at about 20° incidence and the ball spinning steadily along the seam at about 11 rev s−1. The present experiments do not support the popular view that swing increases in damp or humid conditions. In particular, measurements show that the cricket ball seam does not swell in such conditions.