Shallow dents on the surface of the golf ball are a natural choice. Initially, the golf ball surface was smooth. However, the golfer noticed that as the golf ball became older, it would be covered with scratches, potholes and cuts, which seemed to make the ball fly farther. Golfers naturally use gravity to drive golf balls into the fairway, so golf balls are often worn out.
In fact, aerodynamicists have noticed this problem and realized that the scratches and cuts on the surface of the ball are actually a turbulent device that interferes with the air around the sphere and forms a boundary layer. In some cases, the turbulent boundary layer formed by the air near the sphere reduces the resistance of the air and allows the golf ball to fly further.
If you want to explore aerodynamics further, you can tell that there are two types of airflow around the golf ball, laminar and turbulent. The laminar flow has less resistance, but it is more likely to cause a “separation” phenomenon. When the boundary layer of the laminar flow is separated, the resistance of the air is greatly increased due to the formation of the vortex. Turbulence initially has greater air resistance, but its adhesion is better, which reduces the occurrence of separation. Therefore, if the shape of the object is more likely to cause separation, then the best solution is to disturb the boundary layer, which will temporarily increase some air resistance, but in the long run can increase the adhesion of the air and reduce the occurrence of vortices. Without the vortex, the air resistance is greatly reduced. Shallow dents on the golf ball can act to disrupt the boundary layer.
Dent on golf balls is a more suitable way to create airflow disturbances than scratches and cuts. This way the boundary layer is destroyed and the air resistance is reduced, so the golf ball can indeed fly farther.
