Hit hard the golf Ball!!

Golf balls are differently built, some are very simple others are more complex. To get an easy picture about the structure of today's golf balls, we would like to explain the basics as follows: Dimples

In early times golfers made out that irregularities in the surface of the ball would let the ball fly higher and farer. Soon, right after the Gutta Percha balls the so called dimples were purposely printed into the surface of each ball. Still nowadays, most of the ball manufacturers are testing out different shapes and numbers of dimples. The rule goes: the more dimples a ball has, the higher it goes. Then, balls having too many dimples, do fly too high and are lacking distance. Most companies have found their best number of dimples, mostly they are ranking between 300-500 per ball.

Technical background: Well hit golf balls go about 200 km/h (120 m/h). Once off the tee, the ball starts to slow down because because air is sticking to it while flying, just like water sticks to a ball if it falls into water. Since air is sticking to the surface it streams over, it makes sense that the less area on a ball, the less sticking and the less drag there is to overcome. It looks obvious that a smooth coating on a polished sphere would go farther than a ball with a roughed, lemon skinned surface. But, at the speed that golf balls go, it doesn't quite work that way.

Imagine to be a tiny entity, perhaps the size of a micro crustacean - small enough to fit between grains of sand. Now imagine to ride on the surface of a golf ball in flight, or in the wind tunnel at the lab. You realize that right at the surface of the ball, the air is still and it sticks to the plastic as the air molecules are dragged along like syrup running from the rim on a little pitcher at a popular pancake breakfast place. But getting away from the surface, say as far as the thickness of three sheets of paper, we notice that the air is going full speed. Here we're in, what we in golf science call, the "free stream" which moves at 200 km/h. However, the air streaming over a golf ball forms a "boundary layer" of relatively slow moving air. It's distinct. Right at the surface, the air is stuck. A millimeter away from the surface, the air is going full blast. In between - in the boundary layer - it's just slurping along.

That slow moving air in the boundary layer is a source of drag. It lets the air stick to the surface and tumble behind the ball in wild whipping whirlpools. The energy in the boundary layer is lost energy. The tumbling air behind the ball allows a large (relatively large, it's just a golf ball) region of low pressure to form, creating a partial vacuum that would suck the ball back toward the tee. So, the thinner the boundary layer, the less slurpy drag there is, and the sooner the air behind the ball can get back up to the "free stream" speed. The less drag, the farther the ball will be driven.

Here's where the dimples do their job. Dimples make the molecules in the layer tumble. They start roiling against one another. The boundary layer becomes "turbulent." The molecules in the layer are no longer just sliding across the surface gently jostling. Now, they're rolling and bouncing and bumping each other along. When the molecules are in a turbulent boundary layer, they're moving closer to the free-stream speed. There is less of a difference between the speed of the tumbling molecules and the speed of the ball.

It turns out that the air flow in a turbulent boundary layer on a dimpled golf ball is thinner than a smooth or "laminar" flow on, say, a ping-pong ball. Boundary layers are laminar or turbulent, or somewhere in between. We say they're in "transition." Dimples make the transition quick-- not a smooth transition, a turbulent one, ha! (A little fluid dynamics gag there...) When the layer is turbulent and thin, the ball loses less energy to the free stream air. And, drag is lower. Isn't that weird? The dimples make the ball develop less drag.