"Speed bumps" on mirrors?

[Bmwbig6@xxxxxxx]

I've got a weird question (but I need a real answer because I'm not doing 
this for fun).  Can anyone explain to me how the little bumps on the inside 
of most newer BMW mirrors work? I understand they help reduce the noise 
caused by wind buffeting against the window glass, but what physical 
principles are at work? I've heard an explanation using the golf ball dimple 
analogy, but those are dimples and these are bumps. Do the bumps accelerate 
the air past the mirror using pressure differentials, or do they create 
turbulence by interrupting/scattering the airflow? Any light that can be shed 
on this topic would be greatly appreciated. Please e-mail me directly in 
addition to replying here.

Ben Trapp
"Rondell Princess" full of weird questions these days
1990 535iM (Sharked) 

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