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Why Does a Golf Ball Have Dimples?

Shashank Nakate
The reason behind marking golf balls with dimples is to reduce aerodynamic pressure drag. The laminar air flow that drags the ball is converted into a turbulent flow, which makes flight easier and smoother for the ball. Here's more.
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. However, the ball had a short life since it became useless when it came in contact with water.
In 1845, the gum obtained from the Sapodilla tree was used to manufacture golf balls. 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 caused 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. This 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 a ball travels through the air, it faces resistance in the form of friction and pressure drag. 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' formed behind the ball is large. When the surface is marked or rough, the air flows in a turbulent manner. It reduces the size of separation area, since the air doesn't separate earlier, as in the case of a smooth ball. The pressure drag is therefore reduced, and the ball covers a longer distance.
The 'Reynolds number' is an indicator of the transition in the air flow from laminar to turbulent. When the Reynolds number, which is denoted by 'Re', is low, the drag experienced by the ball is less, and vice versa.
The dimples on the golf ball ranges from circular, rectangular, square to hexagonal shape. Round dimples are, however, accepted as standard. Experiments conducted on golf balls show that hexagonal dimples are more efficient than round in reducing drag. Balls manufactured in Britain have 330 dimples, while American golf balls display 336 dimples.
A nice drive and flight for the ball is important in the sport of golf. The idea of dimpled balls was innovative and it has worked wonders for the game.