05-20-2020, 12:15 PM
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#1 (permalink)
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Master EcoModder
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vehicle aft-body and aerodynamic drag
' The main contributions to the drag force originate from the rear part of the body.'
'[L]ow drag can only be achieved when the separation at the rear is eliminated.'
'[I]t is very important to design a rear body surface which brings the divided streamlines smoothly together.'
Wolf Heinrich Hucho, Aerodynamics of Road Vehicles, Second Edition, 1987, pages 61,16,61.
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05-20-2020, 06:42 PM
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#2 (permalink)
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Banned
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Quote:
Originally Posted by aerohead
' The main contributions to the drag force originate from the rear part of the body.'
'[L]ow drag can only be achieved when the separation at the rear is eliminated.'
'[I]t is very important to design a rear body surface which brings the divided streamlines smoothly together.'
Wolf Heinrich Hucho, Aerodynamics of Road Vehicles, Second Edition, 1987, pages 61,16,61.
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Yes that was so in 1987, and remains so for normal road cars today. |
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05-21-2020, 11:56 AM
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#3 (permalink)
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Cyborg ECU
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Quote:
Originally Posted by aerohead
' The main contributions to the drag force originate from the rear part of the body.'
'[L]ow drag can only be achieved when the separation at the rear is eliminated.'
'[I]t is very important to design a rear body surface which brings the divided streamlines smoothly together.'
Wolf Heinrich Hucho, Aerodynamics of Road Vehicles, Second Edition, 1987, pages 61,16,61.
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But of course, we cannot eliminate that separation point entirely on road cars without creating an extraordinary shape with a lot of boattailing. That would be a car nobody could sell, probably. The first Insight had both the tapered track and the Kamm shape and I love it but the market did not. Optimization seems to be the whole game, and it creates some weird shapes. The Caddy CTS seems to me to be just an uglier, sharper-edged Model S, which is also kinda ugly but not terrible.
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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.
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05-22-2020, 12:52 PM
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#4 (permalink)
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Master EcoModder
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the market
Quote:
Originally Posted by California98Civic
But of course, we cannot eliminate that separation point entirely on road cars without creating an extraordinary shape with a lot of boattailing. That would be a car nobody could sell, probably. The first Insight had both the tapered track and the Kamm shape and I love it but the market did not. Optimization seems to be the whole game, and it creates some weird shapes. The Caddy CTS seems to me to be just an uglier, sharper-edged Model S, which is also kinda ugly but not terrible.
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All submarines use 'weird' shapes.
All commercial aircraft use 'weird' shapes.
All sniper ammunition manufacturers use 'weird' shapes
All land speed record cars use 'weird' shapes.
All fuel economy record vehicles use 'weird' shapes.
All rectal suppository manufacturers use 'weird' shapes.
When 'performance' ever actually matters in the world, you'll see nothing but 'weird' shapes.
I'd be forbidden to address things which could address this issue here at EcoModder.com. 
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