In this blog post, we take a scientific look at how the unique dimples on the surface of a golf ball affect its distance.
Modern people are crazy about ball sports. We cheer for Messi and Ronaldo’s exquisite shots, admire Ryu Hyun-jin’s fastballs, and watch Tiger Woods’ tremendous driver shots with bated breath. In this way, we pay attention to the movement of balls and love it. However, among the balls used in ball sports, there are some that are unusually shaped. Most balls are smooth or have only a few lines, but golf balls are different. Golf balls have so many dimples that it is difficult to count them with your fingers. Some people compare them to the stitches on a baseball, the rubber threads on a tennis ball, or the seams on a soccer ball, but considering the relative size of the ball, the dimples on a golf ball are much larger than those on other balls.
In fact, the dimples on golf balls are closely related to the history of golf. Golf began to gain popularity among European aristocrats in the 16th century. Early golf balls were smooth, spherical balls made of wood. However, due to the durability issues of wooden balls, round balls made of leather began to be used. But then, a mysterious phenomenon was discovered. The fact was that balls that had been used for a long time and were bumpy and slightly dented flew much farther than new, smooth balls. This discovery greatly intrigued European aristocrats. In most ball games, new balls help improve performance better than old balls.
The people who solved this problem were researchers at a golf ball manufacturer consisting of mechanical engineers. One of the important fields of mechanical engineering is fluid mechanics, which studies the properties of fluids. This enabled mechanical engineers to analyze the movement of golf balls. This phenomenon can be easily explained by understanding the “drag force acting on objects moving in a fluid.” Drag is the resistance that hinders the movement of a moving object, and a typical example is friction.
The drag acting within a fluid can be broadly divided into form drag and friction drag. Form drag is the resistance caused by the difference in pressure acting on a moving object. For example, when we run 100 meters, the air pressure in front of our body increases and the pressure behind our body decreases, causing resistance called form drag. On the other hand, friction drag is the resistance caused by the viscosity of the fluid. Honey flows slowly from a comb because of its high viscosity, which acts as a resistance that hinders movement. Gases such as air have low viscosity, so the friction resistance of objects moving in air is very small and can be ignored in practice. Therefore, we only need to focus on the shape resistance of golf balls.
When a ball flies, the air flows along the surface of the ball and then begins to separate from the surface at a certain point. When a smooth ball moves in the air, the air flowing over the surface is straight. This is called laminar flow. However, when the air separates from the surface in the middle of the ball, the air speed at the rear of the ball drops sharply, causing a phenomenon called separation. Separation is a phenomenon in which air is separated into two layers, and when the air flow weakens, the air pressure decreases. A large pressure difference occurs between the front and rear of the ball, increasing its shape resistance, so smooth balls fly relatively short distances.
On the other hand, balls with grooves or bumps on their surface cause turbulent flow. Air moves along the grooves on the surface of the golf ball and no longer flows in a straight line. In the case of turbulent flow, the air flow is curved, and separation occurs at the rear of the ball. This reduces the pressure difference and decreases the shape resistance, allowing the golf ball to travel farther.
Ultimately, grooves on the surface of a golf ball reduce the drag acting on the ball, allowing it to fly farther. In this way, engineering knowledge is deeply ingrained in our daily lives and will continue to have a greater impact in the future. This is because engineering knowledge is not just a simple theory, but a powerful tool for understanding and analyzing the world we live in.
