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.