Quote:
Originally Posted by winkosmosis
Well the blister looks too narrow, but I think a gradual transition between the hood and the windshield would obviously allow air to flow smoothly and stay attached, rather than forming a high pressure bubble. I've seen people on this forum say that the bubble means aerodynamics in that spot don't matter, but it seems to me that it's the opposite.
Look the Aptera, Prius, and other aerodynamic cars. The hood is almost the same angle as the windshield so there probably is smooth continuous flow. The question how close to the same angle ideal you can get with a fairing that doesn't connect to the windshield.
Making the transition gradual with a curve has to help. It takes energy to force air to change direction, but less energy if you direct it gradually. Just look at intake pipes, sewage pipes, etc etc... Gradual curves, not right angle elbows.
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The bubble is the locked-vortex that the other air simply skims over.It's also the fresh air source for the cabin and the fan doesn't have to work very hard to bring it in which helps the alternator load( i.e. mpg ).
With respect to Aptera,the majority of air goes around the car,not over.
The Prius,at Cd 0.25 is not demonstrating remarkably low drag for its length/height ratio so I don't know if the zero-zero windshield slope is any quantum leap.
R.G.S White reported the full convex semi-hemispheric windshield as lowest drag as used in Varna,Sunraycer,MG EX-181,M-B C-111 III,Renault Vesta II,McLaren,Honda P-100,GeeBee R-1,USSR' Alpha/Akula/Charlie-class nuclear subs,USS Macon/Akron/Hindenburgh,etc..
Hucho mentions,as others,that if you've got attached flow around the windshield and on to the backlight header,then concentrate on the aft-body,moving the separation point back as far as you dare ( boat-tailing ).