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Old 03-29-2010, 05:42 PM   #15 (permalink)
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golf ball

Originally Posted by eqmos View Post
Yes, but I'm the one who actually saw it.. actually happen

here, I'm not going to rehash all this...

MYTHBUSTERS prove golf ball dimple theory on cars works!!!

the fact is, the golf ball effect, is not limited to balls..

what's all that's required
wind resistance, and solid object, air being acted upon by dimple surfaced object

turbulent flow, via dimpled object, was proven
laminar flow, is undimpled object, is proven
Remember,the golf ball is quite small in comparison to an automobile.Even coming of the tee in a good wood shot at 110-mph,without the dimples,the ball would have a laminar boundary layer and flow would separate before it got to the back side of the ball.
The dimples guarantee an early transition to a turbulent boundary layer,which moves the separation point back behind the ball,reducing it's wake and also the base pressure of the wake for lower drag and a longer drive on the fairway.
An automobile transitions to a turbulent boundary layer at about 20-mph do to it's size in relation to velocity ( the definition of Reynolds Number ).Adding extra roughness can only degrade performance.
I think Bicycle Bob has probably hit on what's going on,that the dimples are behaving like turbulators to feed kinetic energy into a boundary layer on the verge of stalling,allowing the flow to remain attached across a body section which wasn't properly proportioned.
Typically,turbulators cost a drag penalty all the time,but if they reduce form drag more than they aggravate skin friction,there can be a net drag reduction.Proper placement would require rigorous testing.
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