Quote:
Originally Posted by viio
Well I modelled 3 holes into my 1:1 scale 3d model of my car, and ran CFD on it. The holes cut through the bumper and come out in the space behind it which catches some airflow near the spare wheel. The colour contours show air velocity at the back of the car.
Forgive me if I don't rush out and grab a drill - can't see much of a difference.
If anything, the top model (with the holes) appears to have a larger area of low velocity air - hence more drag.
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If you look at pressure I'd expect suction effect across the back. If you look at flow I'd expect characteristic eddy currents to balance boundary conditions with forward flow in the center. Hard to imagine high enough volume of airflow crammed under any car for wake filling in the rear. Bumper holes in the center likely just fuel parasitic eddies. In a fair fight I'd expect a negative return at the pump. It's all conjecture of course. But that's fun too.
