For Tango Charlie
Just joined tonight (UK Time). I was doing a bit of research into some new race car programs and came across the 'Louvres/Louvers discussioin.
Long story short, I reckon you are almost bang on the money. I have put louvres into car panels always wtih the open face away from airiflow. The proifile in side view does not detract from the overall CD of the vehicle as the overall profile will do much more to govern drag and aero coefficients.
However there is alway a low pressure 'dam' at the base of windsheilds and all the louvres but the overall airflow goes past that., thus providing an evacuation effect on that area. This can also be effected by the top view profile of the car and curvature. You can see it in a wind tunnel quite effecifvely. Back to the Fender thing, you are correct in saying that eg. in some LeMans prototype cars the louvre sets can run pretty far back along the top fender surface and this does indeed provide relief to high pressure built up in the Fenderwell due to wheel and tire rotation. In fact most good race cars have greater Wheel and tire offset to bring the rotational "disc' out towards the main body airflow and thus dissipate it that way. Other ways are to use reverse NACA ducts to bring any excess back thru the underbody aerodynamics package to cool both engine, exhaust and rear brakes before putting it to full use via the difusser package to give you the downforce required to keep it hopefully 'glued' down!
Hope it make sense.
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