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Old 05-13-2010, 06:13 PM   #10 (permalink)
COcyclist
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Join Date: Dec 2007
Location: NW Colo
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TDi - '04 VW Golf
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Quote:
Originally Posted by Otto View Post

However, another school of thought holds that undercar flow spreads laterally and such dispersal means less air under the car dragging against the underbody and giving the car unwanted lift. In that case, maybe it's best to use the flow fences to channel the undercar air obliquely out the sides.

Probably best to apply undertray, then tuft test to video actual airflow patterns at highway speed, then install wheel fairings/strakes at whatever orientations best enhance the flow.

Thoughts?
I guess that would depend on whether the main goal is to reduce lift at racing speeds or to reduce drag and lift at highway speeds. I think in my case a smooth underbody that angles upward to the rear of the car can act as a diffuser to help fill the wake and reduce lift. Basjoos uses inner and outer fences between the front and rear wheels to reduce turbulence from the tires. It's hard to argue with his results. I hope to test this myself as soon as I get a free weekend.
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Quote:
Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
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