Quote:
Originally Posted by serialk11r
The tufts were at an almost right angle to the axis of the car, which makes me believe it's coming from vorticity. If the air were seeking a lower pressure region, it would not be able to have so much velocity in that direction at equilibrium. Looking at the paint, the typical "swirl" scratch marks don't exist in that area; the scratches are all at a 70-80 degree angle going inwards towards the engine compartment.
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It makes perfect sense.
There are some photos of the Kamm/K-Fachsenfeld FKFS wind tunnel models which had square body edges down the length of the body.
In the photos you can see the tufts all sticking up into the air,held by the attached longitudinal vortices circulating at these edges.
Their measurements showed that rounding off the intersection cut drag a little over 16%.About Cd 0.174 vs 0.21.
Charles Lindbergh's Spirit of St.Louis suffered from this vorticity.
Ditto for the 1944 WACO CG-4A assault glider.