Review of tennis ball aerodynamics

The aerodynamics of a tennis ball are reviewed here with reference to several wind tunnel measurement efforts. Measurements for a wide variety of tennis balls, including the 'oversized' balls, are presented. Flow visualization results have shown that the separation location on a non-spinning tennis ball occurred relatively early, near the apex, and appeared very similar to a laminar separation in the subcritical Reynolds number regime. The flow regime (boundary layer separation location) appears to be independent of Reynolds number in the range, 167,000<Re<284,000. Asymmetric boundary layer separation and a deflected wake flow, depicting the Magnus effect, have been observed for the spinning ball. Aerodynamic force (drag and lift) measurements for nonspinning and spinning balls are reviewed for a wide range of Reynolds numbers and spin rates. Relatively high drag coefficients (CD?0.6 to 0.7), have been measured for new nonspinning tennis balls. The observed (unexpected) behavior of the tennis ball drag coefficient is explained in terms of a flow model that includes the drag contribution of the 'fuzz' elements.