Why does a Golf Ball have Dimples

Ever wondered why does a golf ball have dimples? Well, the reason behind it is to reduce the aerodynamic drag encountered by the ball during flight. A smooth surface creates a laminar flow, while a marked surface helps create a turbulent flow, which in turn lowers the drag.

History

The golf ball went through many different experiments and tests, before evolving into the form that we see today. Earlier, attempts were made to manufacture golf balls using leather and goose feathers. In order to make the ball hard, the practice of stuffing wet feathers, followed by stitching the leather, was followed. The ball however, had a short life, as it became useless when it came in contact with water. Gum obtained from the Sapodilla tree was used to manufacture golf balls in 1845. These balls were known as gutta-percha balls, because the gum used for the ball contained polyterpene, commonly known as gutta-percha. These balls had a smooth surface which resulted in a shorter drive than the feather-stuffed ball. However, it was observed that marked gutta-percha balls covered a longer distance than the smooth ones. The discovery led to many experiments in golf ball designing and finally the dimpled ball was accepted as the standard one in 1930.

Physics behind the Dimpled Ball

When any ball travels through air, it faces resistance in the form of friction and pressure drag. Friction being the negligible factor, the prime focus is to minimize the pressure drag experienced by the ball. If the surface of the golf ball is smooth, the air that separates behind the surface of the ball, flows in a laminar way. The 'separation area' that is formed behind the ball is large. In contrast to the smooth surface, the air flows in a turbulent manner when the surface is marked or rough. It reduces the separation area in size, since the air doesn't separate earlier, as in the case of a smooth ball. The pressure drag is thus, reduced and the ball covers a longer distance.

The 'Reynolds number' is an indicator of the transition in the air flow from laminar to the turbulent one. When the Reynolds number, which is denoted by Re_cr, is low, the drag experienced by the ball is less and vice versa.

The dimples on the golf ball range from circular, rectangular, square to hexagonal. The round dimples are however, accepted as the standard ones. According to the experiments conducted on the golf ball, the hexagonal dimples are more efficient than the round ones, in reducing the drag. The balls manufactured in Britain possess 330 dimples, while the American golf balls display 336 dimples.

Getting a nice drive and flight for the ball is important in the sport of golf. The idea of dimpled balls was an innovative one and has worked wonders for the game.