Quote:
Originally Posted by aerohead
* The half-body derived from the streamline body of revolution is Cd 0.07538.
* The data is from Sighard Hoerner's 1951 drag table, at Reynolds number = 10-million, reproduced in Hucho's 2nd-Edition, Figure 4.119, page 200.
* There's nothing theoretical about it, since 1923.
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And that is with zero ground clearance, lifted off the ground it is higher than that. I think I remember it as 0.15.
If there is far lower drag coefficient shapes then why are we chasing non-optimal? (non optimal in the sense of not in free air and close to a ground plane, basically where cars are)
Even if the template can predict separation, it would be able to do so only exactly on the centreline, because that is the only place where the flow is parallel to the direction of travel.
I think chapter 4 in Aerodynamics of road vehicles says it best
"In spite of its comparatively low drag, the passenger car is closer to a
rectangular box in terms of fluid mechanics than it is to a body of
revolution, though with refinements in aerodynamics progress is towards
the body of revolution. The flow round a car body is characterized by
separation (Figs 1.1 and 1.2) and its drag is primarily pressure drag.
Attempts to relate drag to primary shape characteristics (see section
1.2.3) have been unsuccessful. The number of parameters describing the
geometry of a car is too large and the interaction of the individual flow
fields too complex."