  The drag on a golf ball can be reduced by dimpling the surface. There have
been few studies, primarily experimental, that provide quantitative information
on the details of the drag reduction mechanisms. To illuminate the underlying
mechanisms, Direct Numerical Simulation (DNS) is applied to the flow around a
golf ball using an immersed boundary method. Computations are performed using
up to 500 processors on a range of mesh resolutions from 61 million points to
1.2 billion points. Results are presented from simulations performed at a
Reynolds number of Re = $1.1\times 10^5$ using a grid of 1.2 billion points.
This video shows the development of instabilities in the near-surface flow, as
well as the delay of complete separation due to the development of local shear
layers that lead to local separation and reattachment within individual
dimples.
