In situ drag measurements of sports balls

Aerodynamic drag on sports balls is typically measured in wind tunnels. There is a concern that fixtures needed to support the ball in a wind tunnel may influence its drag. Measurements under game conditions have been attempted, but are difficult to interpret from the data scatter and are not controlled. The following considers drag measurements from a ball propelled through static air in a laboratory setting. High speed light gates were used to measure drag, including the effects of ball rotation. Drag was observed to depend on the ball speed, rotation, roughness, and orientation. A so-called drag crisis was observed for a smooth sphere and was comparable to wind tunnel data. Rough sports balls, such as a baseball, showed evidence of a small drag crisis that was less apparent than the smooth sphere.