There was a time when golf balls did not have dimples, and yet golfers still sliced and hooked balls. It was only when it was discovered that a rougher surface on a golf ball made it travel farther that the aerodynamics of a golf ball began to be understood, and the idea of applying surface modifications such as dimples was applied based upon scientific principles.
Before we look at modern golf balls, let's have a look at the physics of smooth spheres such as the original golf balls. At one time golf balls were made of a small round leather covering sewed over a filling of feathers - the so-called legendary 'feathery'. However, it would not matter what the covering was or the filling, as long as the cover was smooth the aerodynamics would be the same.
Basically, dimpled or not, a golf ball is a rotating sphere travelling through the air, and is therefore subject to the physical laws of aerodynamics. It had long been known that a lofted club sent a golf ball farther than a straight bladed club such as a putter. The reason was believed to be that because the ball was hit with a club face direct upwards, then the ball would be hit upwards, and therefore travel farther.
This is the same principle of throwing a missile such as a stone or javelin up into the air, rather than straight at the target or enemy, to make it travel farther. Only, a golf ball is moving because it has been hit by a lofted club that places a backspin upon it. Any rotating sphere has a greater air pressure on the side that is moving against the direction of air flow, whether the rotating sphere is moving or static. With driven golf ball the direction of airflow is back to the golfer, in the opposite direction of the movement of the ball.
Bearing in mind that the golf ball has backspin, the bottom of the ball is moving against the direction of airflow, and the top is moving back to you, in the same direction of the air flow relative to the golf ball. There is therefore more air pressure on the bottom of the ball that the top and the ball is lifted upwards. This force continues until gravity takes effect. The greater the speed of rotation of the golf ball, the greater the upward pressure, and this lift will keep the ball in the air longer and hence the ball will travel farther.
The same is true if you slice the ball by putting clockwise spin on it. The left side of the ball (relative to right handers) is moving against the direction of travel of the ball, and hence against the direction of airflow, and therefore promotes a greater air pressure on the left hand side of the ball. That makes the ball drift left and eventually take a severe curve known commonly as a slice.
With the advent of science, the leather golf balls became replaced with smooth balls made of gutta percha, a natural rubber. It soon became noticed that the older worn balls went farther than the new smooth balls, and this eventually gave rise to dimpled golf balls. The science behind dimples lies in the physics of turbulence, and what are known as the Magnus and Bernoulli Effects. These are complex and involve advanced physics, so let's have just a simple layman's look at each so that the effects of dimples are easier to understand.
The Bernoulli Effect relates to boundary layers between the two sides of a revolving sphere moving through the air (i.e. a golf ball). The side moving slower relative to the air velocity around it has less drag on the air and the boundary or turbulent layer of air is relatively thin. The side moving faster against the air velocity has more drag, and so causes more turbulence, and the boundary layer is thicker. The Magnus effect relates to turbulence just downstream of the ball. A rotating ball creates asymmetric turbulence that exerts a pressure on the ball in the same direction as that exerted by the Bernoulli Effect.
Together these two effect act to move the golf ball upwards against a backspin, left against a clockwise spin, and right against a counter-clockwise spin. The latter two explain the slice and the hook, due to the respective spins put on the golf ball to produce each effect. Since this effect is caused by turbulence, it is little wonder that dimples on the surface on the ball increase the effect. They nor only cause a golf ball to go farther, but it is also easier to slice and hook. Theoretically, the poorer players should play with smooth balls, but they are not easy to find these days!
The dimples on modern golf balls have been designed to produce maximum turbulence, although the material of construction of the ball covering is also important. The softer covers allow better use of spin, and since turbulence increases with the speed of rotation of the sphere, then you can get better use of spin in order to stop the ball on the green for example, or bend the ball quickly around obstacles using the Bernoulli and Magnus effects.
However, the softer the ball, the less energy is transferred to it and the less distance you can achieve. Modern golf balls can either have a harder covering to allow more energy to be imparted into the core of the ball for greater distance, or a softer covering for more energy transfer to the spin and better use of the aerodynamics of your golf ball.
The Aerodynamics of a Golf Ball: Why Dimples Make a Ball Go Farther was originally published at http://www.golfplayernow.com