Looking at yet another vortex thread, I was reminded that while automakers go to some length to trip the flow over the top of the car smoothly with a sharp transition, they still have rather large radiui on the sides of a few inches?
So I still don't get how sharp transition is good for the top and radiused is good for the sides. My hunch-made-in-ignorance is that the radiused sides improve crosswind handling at a slight aero penalty, and possibly it is partly aesthetic, and rounded corners on the rear bumper make some sense as well, if you do any bumping. Is it because the top is generally tapered where the sides are not? That is harder yet to comprehend.
Has anyone ever actually tested sharp vertical corners? There are a few seemingly conflicting opinion pages, but I have yet to see results.