Aero near walls?

[raymondu999]

Hey folks; I've just been rewatching the 2007 Season Review DVD; and when it came to the part where Lewis was talking through his Indianapolis 2007 pole lap; you could see that on the straight; Lewis; after getting his exit onto it; steers away from the wall. Lewis says "I had to pull away from the wall because supposedly it makes a big difference to the aerodynamics"

What aero effect would it have, do you think?

[Richard]

I imagine it would make a difference to front wing outwash if it is a long wall and very close, and if outwash was significant for car handling at the moment (ie drag v downforce).

However, I thought outwash only assumed current significance with Brawn GP in 2009?

[raymondu999]

The front wings back then were "in"wash, if that's a correct word

[strad]

DRAG...The boundary of the wall creates drag...sorta like side drafting

[munks]

DRAG...The baoundry of the wall creats drag...sorta like side drafting

I'm not an aerodynamicist, but that's what I've been told as well. Driving next to a wall is basically like driving next to an identical (mirrored) car.

[Dragonfly]

I am quite away from aerodynamics but IMO the car pushes a significant amount of air, like a wave traveling at the same speed. Eventually it interacts with a nearby wall causing some disturbance and affecting the car asymmetrically.

[rjsa]

And at high speeds the wall will suck the car in.

[bill shoe]

Here's a less technical explaination.

A car far from walls will push air around both sides and over/under. If you are close to a wall then you constrain one of the side flow "options" for the air. This means some of the air that previously found it easiest to go around that side now has to go around the other side or around the bottom/top.

Any flat surface near the car reduces airflow "options" and therefore increases drag. Almost any race car shape with a resonably smooth bottom (i.e. any modern F1 car) would have less air drag if it moved through the air (at zero pitch/yaw) without a ground plane.

[scuderiafan]

If you watch the Indianapolis 500, the drivers all go down the middle of the straights, because it does not restrict the flow of air around the sides of the car.

[raymondu999]

So from what I'm hearing; it's kind of like there's a reflection off the wall, or a standing wave?

[sknguy]

Like risa's and bill shoe's explanations, I thought the wall created a low pressure side force (like downforce and drag) between the car body and the wall. You create two areas of low pressure. With Indy cars I'm not sure how they race on ovals but that's my understanding.

[jon-mullen]

Let me see how this explanation goes over...

Picture the car's relative velocity is zero and the air's moving at some free stream velocity before it hits the car. The wall's also moving at that free stream velocity. So, the velocity gradient on the side of the car with the wall would have to be much larger than on the side without the wall. Larger velocity gradient means more shear force. That puts an unbalanced force on the side with the wall and tends to rotate the car about its CG into the wall.

...right?

[strad]

Hmmmm
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