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Old 05-20-2020, 11:37 AM   #1 (permalink)
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Streamline bodies and aerodynamic drag

' Optimum shapes are 'streamlined' bodies having a very slender rear part.'
'[T]he optimum shape in terms of drag is a half-body,which forms a complete body of revolution together with its mirror image - produced through reflection from the roadway.'
Page 61, Table 2.1, 3rd image from bottom,'Streamlined body L/D = 2.5, Cd 0.04
Page 61, Table 2.1, bottom image, streamlined half-body at ground plain, Cd 0.09
Page 15, Figure 1.15 Jaray Half-body (with 'diffuser ),with wheels, Cd 0.13.
Page 39, Figure 1.52 Jaray Half-body, without diffuser, Cd 0.15.
Page 200, Figure 4.120, 1981 VW 'Flow body' ( long-tail), by Buchheim et al., Cd 0.14.
Page 201, ' A closer approach to the value of the basic body without wheels is only achievable through further integration of the wheels into the body.'(Hucho).
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' .... swept full fairings reduced the [ wheel ] drag assembly by about 70%.'
Goro Tamai, The Leading Edge, page 167.
===============================================
With a hand-full of sentences from Hucho and Tamai,it's conceivable to shave the drag of a vehicle from, Cd 0.88, to Cd 0.1064. With off-the-shelf technology.

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Last edited by aerohead; 05-22-2020 at 10:48 AM.. Reason: add missed data point
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Old 05-20-2020, 05:43 PM   #2 (permalink)
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Quote:
Originally Posted by aerohead View Post
' Optimum shapes are 'streamlined' bodies having a very slender part.'
'[T]he optimum shape in terms of drag is a half-body,which forms a complete body of revolution together with its mirror image - produced through reflection from the roadway.'
Page 61, Table 2.1, 3rd image from bottom,'Streamlined body L/D = 2.5, Cd 0.04
Page 61, Table 2.1, bottom image, streamlined half-body at ground plain, Cd 0.09
Page 15, Figure 1.15 Jaray Half-body (with 'diffuser ),with wheels, Cd 0.13.
Page 39, Figure 1.52 Jaray Half-body, without diffuser, Cd 0.15.
Page 200, Figure 4.120, 1981 VW 'Flow body' ( long-tail), by Buchheim et al., Cd 0.14.
Page 201, ' A closer approach to the value of the basic body without wheels is only achievable through further integration of the wheels into the body.'(Hucho).
--------------------------------------------------------------------------------------
' .... swept full fairings reduced the [ wheel ] drag assembly by about 70%.'
Goro Tamai, The Leading Edge, page 167.
===============================================
With a hand-full of sentences from Hucho and Tamai,it's conceivable to shave the drag of a vehicle from, Cd 0.88, to Cd 0.1064. With off-the-shelf technology.
Yes that is technically the case. Of course, you wouldn't then have a practical road car.
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Old 05-22-2020, 10:57 AM   #3 (permalink)
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practical

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Originally Posted by JulianEdgar View Post
Yes that is technically the case. Of course, you wouldn't then have a practical road car.
Some would argue that 'practical' road cars haven't worked out so well for us.
And when a 41-mpg car could have gotten 68-mpg,simply by changing its
shape in 1981, it speaks to an aspect of contemporary capitalistic arithmetic that would certainly disturb Adam Smith.
An Inquiry into the Nature and the Causes of the Stench of Nations.

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