Quote:
Originally Posted by LeanBurn
I was more after whether the air moving down the side of the car would get caught on the wheel well right under the side mirrors or would having the tire more outwards would minimize/eliminate it, not so much how much turbulence the wheel itself created. If it was as the drawing above suggests the "fan-like" turbulence created by the wheel would push the air to more align with the rest of the body side that would be great. If the fan-like turbulence is negligible then there is more of a chance the air gets snagged on the wheel well, creating drag. If the wheel was pushed out to more in line with the body air would have less of a chance to get caught there.
|
If the car was always in still air the wheel wells would be in train with the side of the car.Momentum would tend to carry the air straight back,although if you've been besides cars in the rain you may have seen air blasting out the front wheel wells as engine compartment air makes its escape from the body.
Observations have firmly established that cars are exposed to some crosswind most days.I believe that the SAE tests with a 7-degree crosswind @ 7mph for 18-wheelers.
In this case,if you're NOT going to cover the openings,then 'flush' wheels would have an advantage,as they would help block the windward transverse vector of the apparent wind which might otherwise trigger flow separation when snagging the trailing leading edge of the wheelhouse(s). 'MOON' -style wheel covers would also help.
Ford Motor Co. discovered a 9% drag savings for their Probe-IV with spat enclosures of the front wheels,which were shielded additionally with an elastic urethane skirts.