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California98Civic · 08-30-2020, 11:04 AM

But it is not a CFD study. The author used pressure taps on a 1:4 scale model developed by BMW/Audi and tested it in a wind tunnel. The flow visualizations were done with paint on the body in the wind tunnel. Everything about the two shapes is standard except the slope of the roof/backlight/trailing edge.

That the modest change in the slope angle and curves on the fastback yields higher pressure readings on the roof is interesting. If the pressure readings along the backlight and decklid drop quickly to lower than the notchback, might it be possible that this particular fastback becomes too fast after the roof AND that the pillars are not optimized well?

If the vortices are the problem and the fastback shape is otherwise known to have more potential for reducing drag and lift when undertrays, diffusers, spoilers, and fins are used, then why not explore reducing the vortices off the pillars by tapering and radiusing the fastback's full rear body contours more? We might be able to get Cd possibly under 0.20 and lower lift too.

That kinda is a description of the XL1, which even narrowed the rear track. The XL1 was speed limited possibly because of higher lift over 100 MPH. But lift at high speeds could be dealt with through other optimizations or active aero. We'd have an ultra low drag body and no lift problems at 150 MPH.

I would love to find a contemporary study in automotive aerodynamics where some grad student tests an abductively reasoned thesis like this.

Here again is the link to the article (I previously posted it in post #58):
https://ecomodder.com/forum/showthre...tml#post630095

08-30-2020, 11:04 AM	#83 (permalink)
California98Civic Cyborg ECU Join Date: Mar 2011 Location: Coastal Southern California Posts: 6,299 Black and Green - '98 Honda Civic DX Coupe Team Honda 90 day: 66.42 mpg (US) Black and Red - '00 Nashbar Custom built eBike 90 day: 3671.43 mpg (US) Thanks: 2,373 Thanked 2,174 Times in 1,470 Posts	But it is not a CFD study. The author used pressure taps on a 1:4 scale model developed by BMW/Audi and tested it in a wind tunnel. The flow visualizations were done with paint on the body in the wind tunnel. Everything about the two shapes is standard except the slope of the roof/backlight/trailing edge. That the modest change in the slope angle and curves on the fastback yields higher pressure readings on the roof is interesting. If the pressure readings along the backlight and decklid drop quickly to lower than the notchback, might it be possible that this particular fastback becomes too fast after the roof AND that the pillars are not optimized well? If the vortices are the problem and the fastback shape is otherwise known to have more potential for reducing drag and lift when undertrays, diffusers, spoilers, and fins are used, then why not explore reducing the vortices off the pillars by tapering and radiusing the fastback's full rear body contours more? We might be able to get Cd possibly under 0.20 and lower lift too. That kinda is a description of the XL1, which even narrowed the rear track. The XL1 was speed limited possibly because of higher lift over 100 MPH. But lift at high speeds could be dealt with through other optimizations or active aero. We'd have an ultra low drag body and no lift problems at 150 MPH. I would love to find a contemporary study in automotive aerodynamics where some grad student tests an abductively reasoned thesis like this. Here again is the link to the article (I previously posted it in post #58): https://ecomodder.com/forum/showthre...tml#post630095 __________________ See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.