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Old 01-27-2010, 08:23 PM   #15 (permalink)
Moderate your Moderation.
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Originally Posted by KamperBob View Post
I agree. Look at most trucks' head-on silhouette. Height is comparable to width. But there are two sides to go around and only one top to go over. So my bet is more air pushes around the two sides combined than goes over. Sure some goes under too but that has to be the least given the road constraint. I think side profile analysis (top and bottom flow) is less than half the total. Top view analysis (flow on both sides) cannot be neglected on a truck if the real goal is optimizing in 3D. Cars? Maybe...

My 2c
Even in cars, side flow interferes greatly with top flow. The effect can be noted in a wind tunnel with multiple smoke streams, where one will suddenly diverge from it's "apparent" path. Without seeing all the other flow lines, one might not be able to explain this, but having seen the "rest of the equation", so to speak, one can then understand that flow does not necessarily proceed in a straight curve or an "apparent" arc over or around an object in a fluid.

I think that many of us fall victim to looking at profile flow as opposed to plan view because some of the most aerodynamic vehicles appear to pay specific attention to profile. I think we neglect to notice that their profiles are also much, much smaller than even our smallest cars.

Since lift can occur in any vector, (you change it's name to understand directionality, but the force remains the same) side flow is just as important, if not moreso, since it represents 2/3 of the exposed aerodynamics equation (roughly).
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