Numerical Investigation of the Effect of Rotational Speed on the Flow past a Golf Ball*

Unsteady aerodynamic forces acting on a rotating golf ball and flow structures were investigated using Large Eddy Simulation combined with the moving boundary method. The computational domain was discretized based on the unstructured high-resolution meshes and the first wall-nearest grid is less than 1 in the dimensionless wall distance y plus. That was because to capture the detailed flow structures near the ball surface and predict aerodynamic forces with high accuracy. The Reynolds number based on the ball diameter and the uniform flow velocity was 1.1×10⁵, which is the supercritical region in a dimpled sphere, and the rotational speed was set to the spin parameter Γ = 0.1. In this study, the focus was on the effect of rotational speed on the same golf ball. As a result, both drag and lift increased as the rotational speed was increased. For the difference of flow structures, it was found that the separation lines changed due to the rotational speed. Moreover, there was a difference in the strength of downwash and a pair of longitudinal vortices generated behind the ball.