Wheel wake

[XJguy]

I am a bit perplexed...will have to look this up, but perhaps some of you already have.

With regards to the turbulent air behind a rotating wheel. In most race cars the rule is to provide as clear a path for the air that interacted with the wheel as possible. You'll see vents immediately behind the front wheels, as well as tunnels for the rear wheel air. I see this as a solution to two problems, wind drag, and brake heat. However in some cars I see fairings that approach the ground located immediately behind the wheel and come to a sharp taper behind the wheel.

So the question is, which of these will result in better aero?

[Joenavy85]

uh, err, um.... good question, i would think that the less back there that there is to catch the air the more aero it would be, but then again it may be better to try to close up the area behind the wheel and put on fender skirts to minimize the turbulant air to begin with

[XJguy]

Fender skirts and smooth wheel covers are a given, but I am really curious about the area immediately behind the wheels. As long as the wheels spin and touch the ground they will act as pumps and bring air into the wheel well housing, and the wheel well opening itself will allow air in, it would seem to me that letting that high pressure air escape as fast as possible would be the most aerodynamic thing to do, race car engineering seems to agree. But very often I see quite the opposite, especially on non, high performance aero cars. I am wondering if its for aesthetic appeal to the general public, or if there is proven science behind it.

[Joenavy85]

where's aerohead when you need him?

[akumabito]

Maybe it's a compromise on road cars? large ducts and tunnels are not the most practical things on road-going vehicles after all, especially when you want to optimize interior space.. I could very well be completely wrong though..

It could also be a compromise on the part of high-performance vehicles: sacrificing a little aero in favor of more downforce?

[Bill in Houston]

Ya, those guys sacrifice a lot of aero to generate downforce. Their Cd is huge.

[mort]

Originally Posted by XJguy

So the question is, which of these will result in better aero?

Hi XJguy,
This problem has been studied and solved for small planes with fixed landing gear.

For cars there are other considerations, but as for minimum drag, fairings are best.

-mort

[Nevyn]

Is it for aerodynamics on race cars, or is it for downforce?

[Joenavy85]

Originally Posted by Nevyn

Is it for aerodynamics on race cars, or is it for downforce?

IMHO it depends on the car, on Formula 1 cars it's almost all for downforce; on NASCAR cars, it's almost all aero

[XJguy]

Originally Posted by mort

Hi XJguy,
This problem has been studied and solved for small planes with fixed landing gear.

For cars there are other considerations, but as for minimum drag, fairings are best.

-mort

I can see that as being the case for a plane where the the concern is drag while in the air. But on a car the wheels rotate pumping air up and over into the wheel bay/well.