Why Does A Golf Ball Have Dimples?
A golf ball can be driven great distances down the fairway. How is this possible? The answer to this question can be found by looking at the aerodynamic drag on a sphere without dimples (while it's flying through the air!). The first kind of drag is the obvious drag due to friction. But, this is only a small part of the drag experienced by a ball. Most of the drag comes from the 'separation of the flow' as the ball sails through the air. For laminar (smooth) flow past a sphere, the flow separates very early. Compare this with a 'turbulent flow', caused by a marked or dimpled surface. Flow separation is delayed. The larger (or early) flow separation causes a larger pressure drag on the sphere (golf ball). The rough or dimpled surface causes 'turbulence' which delays or narrows the flow separation. This lowers the pressure drag. On a smooth sphere (golf ball) the faster the ball moves, the more drag is produced. On a rough sphere, speed does not change the drag very much.
Although round dimples are accepted as the standard, many other shapes were tried. Hexagons (six sided) resulted in lower drag than round dimples, so maybe in the future we will see golf balls with hexagonal dimples.
About the Author
Jani Macari Pallis, PhD
Dr. Jani Macari Pallis is the founder of Cislunar Aerospace, Inc. She is also the creator of two excellent educational sites, The K-8 Aeronautics Internet Textbook, a multi-level interactive learning website, and Wright Again, a chronological history of the Wright Brothers.