The lateral force on a spinning sphere: Aerodynamics of a curveball

Abstract

The lateral force on a spinning baseball in a wind tunnel has been measured. The magnitude of the force is nearly independent of the orientation of the seams of the ball. The drag coefficient appears to be at most weakly dependent on Reynolds number and to be principally a function of the ratio of the rotational speed of the equator of the ball to the wind tunnel speed. This is to be compared to the work of Briggs, which implies a strong effect of Reynolds number on the drag coefficient.