Whether you’re a golf enthusiast or just passing by a package of golf equipment in a store, you may have wondered why the sport’s round white balls have hundreds of tiny depressions on their surface. Are these dimples just for appearance or do they serve a purpose?
As it turns out, the dimples make the game of golf possible. The depressions facilitate aerodynamic optimization, or the ball’s ability to travel longer distances, by affecting the lift and drag of an object in the air. (Lifting is in the direction perpendicular to movement; pulling opposes movement.) According to Scientific American, a dimpled ball moves twice as far as a smooth one. This is because the dimples create an air boundary around the ball, reducing both airflow and drag. They also act as turbulators that induce turbulence in the layer around the ball.
The design also adds to the buoyancy of the object, with about half of the buoyancy being the result of the ball’s rotation and the other half being a product of optimizing the buoyancy force from the dimples.
The overall result is that the air flows more evenly around the ball and the air in front of it moves faster. The ball is essentially in the middle of a perfect aerodynamic sandwich, with higher pressure behind it pushing the ball forward and lower pressure in front of it, which allows the air to move faster.
The depth of the dimples can also make a big difference. A typical golf ball has 300 to 500 dimples with an average depth of 0.010 inches. Most are spherical in shape, although some companies have adopted a hexagonal shape to further reduce drag.
Golf balls weren’t always pockmarked. Early players used smooth balls, but found that the more a ball was nicked and damaged, the further it traveled. With a golf ball, shape definitely follows function.
[h/t Scientific American]
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