Magnus effect on a rotating soccer ball at high Reynolds numbers: Fid-Bau Portal

Magnus effect on a rotating soccer ball at high Reynolds numbers

Kray, Thorsten / Franke, Jörg / Frank, Wolfram

Abstract The Magnus effect on a prototype model soccer ball rotating perpendicular to the flow direction at Reynolds numbers in the range of $0.96 \times 10^{5} < R e_{D} < 4.62 \times 10^{5}$ was investigated by means of aerodynamic force measurements and of a flow field survey. Experiments were performed using a rear sting support where the soccer ball was split into two halves that were driven by a motor inside of them. In the non-rotating state the variation of force coefficients with Reynolds number and boundary layer separation points are within the range that is found for real soccer balls. In the rotating-state, considerable changes of the mean force coefficients with Reynolds number $R e_{D}$ and spin parameter $S P$ occurred, which can be attributed to the altered boundary layer separation. These changes also lead to significant changes of size and deflection of the wake zones in the lateral direction. A negative Magnus effect occurs in the critical Reynolds number range. Positive Magnus force is induced when the boundary layer is either laminar or turbulent on both sides of the rotating model soccer ball.

Highlights • Experimental investigation of the Magnus effect on a rotating soccer ball. • Dependence of aerodynamic force coefficients on Reynolds number. • Effect of surface roughness and rotation on boundary layer separation. • Visualization of the positive and negative Magnus effect. • Effect of support interference on boundary layer separation.