This question has probably been asked a million times, but I'm trying to understand the fluid mechanics behind swing, and was hoping someone would be able to help me.
Lots of the material I read online about the mechanism of swing talks about the the asymmetrical wake formed, which creates a pressure differential, which pushes the ball to one side. I have not found anywhere which explains where this pressure differential however.
For example, if we say the the wake is a low pressure region, and the pressure differential is between the high pressure stagnation point at the leading edge of the ball, and the low pressure stagnation point in the wake, then since the wake is angled, the form drag caused by this pressure differential will cause lateral motion. However, since the force will point from the high pressure stagnation point to the low pressure stagnation point, the resultant lateral force is actually in the wrong direction to the actual direction of swing.
I think I can explain it with the right direction of swing by relating it to lift on an aerofoil. The wake is angled which causes a deflection of the airflow, which causes an equal and opposite force which pushes the ball in the correct direction. The magnitude of this force should be calculable with the lift equation. However, I never see any link between lift and a cricket ball in any of the papers I've read so far. (Note, when I say lift I mean to relate this force to how the lift force is created, obviously this force is a horizontal force perpendicular to the direction of motion of the ball in this case, not a force causing it to rise)
Can someone explain if I can use this lift idea to explain swing? And what I'm getting wrong with the pressure differential way of explaining it?
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