[Aerodynamics] Why does the drag coefficient increase after turbulence

[PhyIsOhSoHard]

As you can see, around Reynolds number of 5 10⁵ the transition occurs for a smooth sphere.

However, why is it that after this transition that the drag coefficient increases at turbulence?

 

[rcgldr]

A lot of the drag for a sphere is related to the size of the wake induced behind the sphere. The drop in the curves corresponds to the air tending to stay attached longer to the surface of the sphere, reducing the size of the induced wake, and decreasing coefficient of drag. As the speed continues to increase, the wake starts to increase in size again.