The shape of golf ball is one of the achievements of aerodynamic research. This is related to the turbulent transition and separated flow around the sphere.
When a smooth sphere flows around, the transition of turbulence occurs late, and the regular flow corresponding to turbulence is called laminar flow. However, the laminar boundary layer is easy to flow.
The phenomenon of detachment (that is, the streamline leaves the surface of the ball), a high pressure area is formed on the front of the ball, and a large low pressure area is formed on the back of the ball, resulting in great resistance (piezoresistance). Let the golf ball fly a short distance
However, when there are dents on the surface of the sphere, the dents promote turbulent transition, and the turbulent boundary layer is not easy to produce flow separation, thus reducing the low pressure area behind the sphere and reducing the resistance. Thereby increasing the flying distance of the golf ball.
The frictional resistance of turbulence is greater than that of laminar flow, but compared with the shape resistance, the effect is smaller and the total resistance is still smaller.
Small protrusions on the surface of golf ball can also promote separation, but the interference of protrusions on the flow is somewhat difficult to control, resulting in some lateral forces (also called lift).
Regular flow around a sphere has no lift. Rotation will produce lift. Appropriate lift-drag ratio will increase the flight distance. Different rotation directions will produce a "banana ball" effect.
In addition, the rules of golf stipulates that golf balls must not be designed, manufactured or intentionally changed to have different characteristics from spherical symmetric balls.