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Old 05-20-2020, 05:43 PM   #2 (permalink)
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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.
Modifying the Aerodynamics of Your Road Car

A really good book that should be added to the library of everyone working in automotive aerodynamics, as well as those making car aero modifications at home. - Rob Palin, former Tesla aerodynamicist
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