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Old 06-13-2018, 12:47 PM   #733 (permalink)
aerohead
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Quote:
Originally Posted by Tesla View Post
I've been pondering on this for a while now and I think we are coming to the limits of this process, as I understand it we have experimental data and experience which suggests a teardrop type shape with probably a bit less than the 2.5:1 ratio as being the ideal. The risk being that the penalties accrue much more rapidly below 2.5:1 than above if something goes awry. Then there is the real world where appendages change the story whether you are a fish, bird or motor vehicle.
Unless we can determine any other specific mathematical relationships, without extensive testing it is hard to determine what the ideal distribution along the curve would be.
My personal thoughts are that something of an S-curve might be the ideal where the angles accelerate rapidly through to 70-80% and then begin to taper back towards horizontal so that the converging air streams are aligned in a parallel manner. The Parametric equation had this characteristic, but any online search for teardrop equations will produce dozens of results, but which one is best?
*Hucho suggested that with fully-integrated wheels,we might achieve Cd 0.08.
*A streamlined body of revolution of L/D= 2.5 would be the basis.(Cd 0.04)
*These shapes are incapable of flow separation,the single most important consideration to aerodynamic streamlining.
*The 1983 Ford Probe-IV (not that unusual looking),as a 'camera' car would be Cd 0.137.This car could have been mass-produced in steel and glass in 1986,at no more cost than a Ford Escort.(36-month product cycles are nothing new)
*At Cd 0.137 we could have endeavored to go below that value,exploring the more organic shapes known to produce lower drag.
*We've lost untold $billions by not doing it.
*The automotive manufacturers may represent the only industry in which technological innovation means nothing in product design.
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