Visualization of flow over a golf ball at Re = 110,000
  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. 
Clinton Smith, Nikolaos Beratlis, Elias Balaras, Kyle Squires, Masaya   Tsunoda