Quote:
Originally Posted by freebeard
Some guy named PRK in 2012:
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What surprises me is that buses #1 & #2 (bumper to bumper) retain their Cd regardless of whether bus #3 is tailgating them or not (1st and last example).
I would think that #3 would somehow impact #2's Cd, even if to lesser effect than #2 did for #1.
Maybe we need to look at #1 + #2 as 1 vehicle, check its Cd, and see how #3 effects that?
Quote:
Originally Posted by freebeard
I picture the wake as tiny, invisible clutching fingers, trying to drag the car backward, reletively speaking. The pressure difference can creep forward behind some certain body features, presumably the tail end of the wake (small narrow and close to the ground) can influence the parts further forward.
Push the bow wave of a second vehicle into it and counterintuitive things might hanppen.
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I saw those "clutching fingers" also as proportional to the surface area of the wake's cross section, more or less. Not sure how wakes with same area but different perimeters compare? Going OT, sorry.
How the wake "pulls" the vehicle back is already difficult for many people to imagine, it takes a good imagination. But how the presence and distance of a tailgating vehicle effects the wake isthe next level of abstraction for me.
It seems to imply that those "clutching fingers" depend not only on the area of wake, but also on its length? So it is a 3 dimensional problem, not 2D. Plus speed adds yet another dimension... Wild.