Quote:
Originally Posted by freebeard
My understanding is that The Template is a half body of revolution to insure that air doesn't want to move laterally because of pressure differentials between the top and sides, which leads to vortex generation.
If that's the case, wouldn't a half-square cross section serve as well, given equal cross-sectional area? If air is not wrapping across the edge, would no vortexes be created?
Here are three aeroforms, a cylinder, a superellipse and a square. Would their Cd be equivalent?
(These are not dimensionally highly accurate; I just eyeballed the proportions against The Template)
The next question: If the height/width proportion changes, what happens to the respective tapers? If the half revolution form is 7' wide, then it is 3 1/2' high. If the height is proportionally greater, does the side taper increase or relax?
TIA |
I've been chugging back through Aerodynamiks des Kraftfahrzeugs by Koenig-Fachsenfeld and looking at material he worked on under Kamm at the FKFS which is germane to the 'organic' vs 'cubist' teardrops.
It looks like they tested both images (left) and (right) as passenger car bodies,with wheels,at 'standard' ground clearance.
The (left) body produced Cd 0.12,the (right) body Cd 0.21.
I've contacted a local German tutor to help with translation,but from the tabulated data I think this is what they found.
FIAT,in a 1986 SAE paper investigated fastback bodies and demonstrated how the Cd is corrupted without both tumblehome and edge rounding,something which is a feature of the body of revolution.
Jaray cheated the form with his pumpkin seed of 1922 so we've got 'options.'
I'll try and have something for Saturday at the latest.