The golf surface is intentionally made with many dents.
The shape of the golf ball is one of the results of aerodynamic research. This is related to the phenomenon of turbulent flow and separation of the flow around the sphere (ie, the flow around the sphere).
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When a smooth sphere flows around, the turbulent transition occurs later, and the regular flow corresponding to the turbulence is called laminar flow. The laminar boundary layer is more prone to flow separation (ie, the streamline leaves the surface of the ball), the sphere forms a high pressure zone on the face, and the back surface forms a large low pressure zone, which generates a large resistance (pressure difference resistance). The distance the golf ball is flying is small.
When the surface of the sphere has a dent, the dent causes the turbulent flow to occur, and the turbulent boundary layer is less prone to flow separation, thereby making the low pressure zone behind the sphere smaller and reducing the resistance. Increase the distance the golf ball flies.
The friction of the turbulent flow is larger than that of the laminar flow, but compared with the shape resistance, the effect is small and the total resistance is still small.
The small protrusions on the surface of the golf ball can also play a role in promoting separation, but the interference of the protrusions on the flow is somewhat difficult to control, causing some lateral forces (also called lift).
There is no lift in the regular flow of the sphere. Rotation produces lift. A suitable lift-to-drag ratio will increase the flight distance. Different directions of rotation will result in a "banana ball" effect.
In addition, golf rules dictate that golf balls must not be designed, manufactured, or intentionally altered to have characteristics that are different from sphere symmetry.
