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Old 09-15-2018, 12:32 PM   #14 (permalink)
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pressure wave/slope

Originally Posted by kach22i View Post
Thank you for finding it, that was a good thread.

Brings to mind a new question though; when a car is lowered so much and chin spoilered so much that it almost behaves like a surface blister, does the pressure wave change enough to warrant an optimized shape change?

That is to say, the lower you go, the more slope you need at the front?


And in the same vein of thought; the higher you go the more important it is to curve the chin inward and not have an abrupt splitter-like "cut-off" that could cause turbulence below it.

Or are these two different phenomena?
I'm not certain that I fully understand the question,but I'll throw this out.
*The bulbous nose,as on the Template is ideal.There's nothing you can do to lower the drag.All you're trying to do is provide for the approach angle and achieve attached flow.If you extend the nose further forward it won't improve flow attachment (you're already there),and the added surface friction will increase drag.With around 40mm of radius under the chin spoiler,you're golden.
*Ground clearance doesn't change the flow,other than the consideration that,you've got to have ground clearance around town so you don't tear the front and rear end off the car,or high center in the middle.
*On a perfectly smooth highway,with no road kill laying in the lane,you could drop the car 'into the weeds' and get closer to the drag minimum,or just leave the clearance alone and do full wheel fairings.
*The only pressure you're concerned with is that produced by separation.With the template,there is no separation and there's no lift.The high pressure at the nose and tail cancels any Bernoulli lift due to flow acceleration.
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