Why do golf balls have bumpy dimples instead of smooth ones, and how do they affect airflow and distance?

The dimples on the surface of a golf ball are more than just a design feature, they play an important role in the ball’s distance. The dimples hydrodynamically reduce air resistance, delay flow separation, and reduce pressure differentials. This allows the ball to fly farther and more steadily, and the difference in distance is nearly double when compared to a smooth ball.

 

Anyone who has ever looked closely at a golf ball remembers seeing dimples, or bumpy grooves that cover the surface. This unique surface is enough to make anyone wonder. Why are dimples there? Are golf balls bumpy simply because they need to fly farther? Common sense would suggest that a smooth surface would be better for sending the ball farther. This is because a smooth surface would seem to reduce air resistance. In fact, for many flying objects, especially airplanes, the goal is to minimize air resistance by keeping the shape as streamlined and smooth as possible. So why is this bumpy surface so unique to golf balls? To answer this question, we first need to look at the history of golf balls when they were first created.
When golf balls were first created, all balls had a smooth surface. At the time, golf was primarily a sport for the aristocracy and upper class, and balls made with the technology of the time were usually handcrafted using leather. These early golf balls were not only simple to make, but also beautiful to look at, thanks to their smooth surfaces. But over time, golfers noticed something interesting. Balls with rougher surfaces that had been used for a long time traveled farther than newer, smoother balls. How could a ball with a rougher surface travel farther? This discovery left many golfers puzzled at the time and has since been studied by scientists.
To answer this question, we need to understand a little bit about hydrodynamics. When an object flies through the air, there are four different forces that act on it. First, thrust, which is the force that propels the object forward. Second, lift, which helps keep the object from sinking. Third, drag, which impedes the object’s motion. And finally, Gravity, which pulls the object to the ground. Of these forces, the one that is relevant to the dimples on a golf ball is drag. There are two types of drag. The first is frictional drag, which is caused by the friction between the fluid and the surface of the object, and the second is pressure drag, which is caused by the pressure difference between the back and forth when the object is moving. In general, friction increases when the fluid is more viscous, the surface of the object is rougher, or the object has a larger surface area. Pressure drag, on the other hand, depends on how streamlined an object is; the more streamlined an object is, the less pressure drag it experiences.
A golf ball is not as streamlined as an airplane, and its small size means that it has less surface area in contact with the air. Therefore, it is more affected by pressure drag than friction drag. Let’s take a closer look at how pressure drag works. When a non-streamlined object is flying through the air, the air around the ball initially flows along the surface of the object, but as it reaches the back of the ball, it is pulled away from the surface. This is called ‘flow separation’. The airflow doesn’t follow the surface of the object all the way around, leaving the back of the ball in a vacuum. This causes the front of the ball to have a higher air pressure and the back to have a lower air pressure, creating a strong pressure differential from front to back. This pressure difference creates a force that pushes the ball backward, called pressure drag.
This is where the dimples on the surface of the golf ball play an important role. They”re not just a decorative element, they physically add momentum to the fluid. When air passes over a bumpy surface with dimples, the airflow is irregularly disturbed by their shape. This adds momentum, causing the airflow to follow the surface of the ball for a longer period of time. In other words, the dimples delay flow separation. The delayed flow separation reduces the vacuum that forms at the back of the ball, which in turn reduces the pressure drag.
Another important effect caused by dimples is rotation. Golf balls usually rotate at impact, and this rotation also affects the distance and direction of the ball. In particular, a ball with backspin will fly more stably and travel farther thanks to dimples. Smooth balls without dimples don’t induce the same airflow, resulting in a relatively short distance. In fact, if you compare the distance between a smooth golf ball and a golf ball with dimples, you’ll see a difference of almost two times.
In conclusion, dimples on a golf ball play an important role in effectively reducing air resistance and improving the ball’s distance. Thanks to the dimples, the ball can fly farther and more stably. This scientific design of golf balls has evolved over time through experience and research, and is an important factor in helping golfers maximize their skills.