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Old 04-10-2015, 02:08 PM   #1 (permalink)
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Rotating wheels effect on aero (CFD picture)

I was reading an article about aerodynamics this morning and stumbled upon this picture. I thought it was interesting enough to post it up.

Blue is low air speed, red is high air speed.


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Old 04-10-2015, 02:34 PM   #2 (permalink)
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Looks like most of the wake width is coming from the front wheels. Am I seeing that right?

Thinking of "velocity varies inversely with pressure" makes this image more meaningful to me.

This is the view from below, correct?

Last edited by mwilliamshs; 04-10-2015 at 03:51 PM..
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Old 04-10-2015, 03:14 PM   #3 (permalink)
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Do we know the vehicle that was tested ? It would be interesting to see the wheel design / wheel well clearances.
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Old 04-10-2015, 04:09 PM   #4 (permalink)
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Quote:
Originally Posted by mwilliamshs View Post
Looks like most of the wake width is coming from the front wheels. Am I seeing that right?

Thinking of "velocity varies inversely with pressure" makes this image more meaningful to me.

This is the view from below, correct?
This is a bottom view, and a lot of the wake is coming from the wheels. Farther up on the body, this probably isn't true, but we are looking from the bottom.


Quote:
Do we know the vehicle that was tested ? It would be interesting to see the wheel design / wheel well clearances.
Nope, I provided all the data they did in the article.
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Old 04-10-2015, 05:38 PM   #5 (permalink)
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Quote:
Originally Posted by Cd
Do we know the vehicle that was tested ? It would be interesting to see the wheel design / wheel well clearances.
Whatever it is is weird. The wheel (+ tire?) diameter is 1/5th the vehicle width. If the 'saloon' is six feet wide, it must be running 14" rims with no tires.

The wake from the rear tires appears to be almost as great. Probably down to the differing height of the wheelwell arch.
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Old 04-10-2015, 10:07 PM   #6 (permalink)
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Quote:
Originally Posted by freebeard View Post
...The wheel (+ tire?) diameter is 1/5th the vehicle width. If the 'saloon' is six feet wide, it must be running 14" rims with no tires...
I think the gray circles are tire contact patches, about 14" diameter by your math, which is about right I'd think

Last edited by mwilliamshs; 04-14-2015 at 05:56 PM..
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Old 04-14-2015, 04:32 PM   #7 (permalink)
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from below?

Quote:
Originally Posted by mwilliamshs View Post
Looks like most of the wake width is coming from the front wheels. Am I seeing that right?

Thinking of "velocity varies inversely with pressure" makes this image more meaningful to me.

This is the view from below, correct?
The CFD is representing the road as a pane of glass,and we're seeing the velocity distribution at the road surface only,right at the contact patch.
The front tires are creating part of the bow wake and the rear tires are embedded within their turbulence.
Luminescent soap smears will reveal the same pattern on the floor of a wind tunnel and with a telephoto lens,you'll see the same thing on a dusty road.

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