Quote:
Originally Posted by freebeard
A wing in free air is not the same. It's lift in complex. Bernoulli effect is only part of it (camber, angle of attack).
I'd say the ground vehicle is more comparable to a wing tip.
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Yes. A wing can be considered as a 2D section (this is how the understanding of aeronautics was developed). However, the flow around a car is highly 3-dimensional, which is why every textbook I have cautions against trying to apply an understanding of aeronautics directly to cars.
That said, while a "wing in free air is not the same," the
mechanism at work may be the same: airflow "wrapping" around the roof causes an increase in flow speed and reduction in pressure--but of course the ramifications of that are more complex than on a 2D wing section. For example, I found by direct measurement that the flow speed over the Prius' roof is faster toward the middle and slower toward the outside edges, and that this situation is reversed over the rear window.