Quote:
Originally Posted by JulianEdgar
Aerodynamics of Road Vehicles (5th edition - Pages 298 - 299) has a crystal clear diagram and description of rear lift variation with squareback and fastback configurations.
The diagram:
Note how lift decreases as the shape moves from fastback to squareback ie a fastback shape has higher lift.
The description:
Note how the explanation has nothing to do with flow separation but instead to do with the airflow wrapping around that rear fastback curve.
So this is of course yet more evidence that Aerohead's theory of lift on modern car shapes is completely wrong.
(I should add that the book defines a fastback as having attached flow to the trailing edge of the car.)
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1) the diagram depicts a squareback and notchback.
2) for a fastback vs notchback vs squareback comparison, please see Hucho's 2nd-Ed Figure 5.9, page 221.
3) the notchback has a higher CL at 0.5085, than the fastback, at CL 0.4500. The squareback does, clearly have the lowest CL, 0.2390.
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4) if the air WAS actually 'wrapping' the fastback, it would have the highest static pressure available, and lowest possible lift, simply as a function of the Bernoulli theorem, by definition. This is what your team of five have overlooked in their perusal of your book.
5) For the VW Polo / Golf / Scirocco, prismatic body type research, the Cd minimum was at the 'template'.
6) as the slant angle increases, vortex drag is being introduced, which steadily increases until maximum @ 30-degrees, then 'vortex-burst' transforms to wake to a squareback wake, large, but vortex-free.
7) ' The highest drag ... results from vortex drag.' Hucho, page 149, 2nd-Ed.
8) Your Dr. Thomas Wolf said the rear spoiler on the Porsche ' creates a stronger negative pressure gradient.' This would be impossible unless the air wasn't 'wrapped'.
9) the issue is the co
10) and going back to Hucho's comment about aerodynamic drag of road vehicles, it's a function of pressure drag. And pressure drag is a function of separation. Separation is a function of body shape.
11) total drag includes vortex drag, which is implicated in Cd.
12) if you want to see the 'template' at work, consider the Cd 0.31 Aston Martin Cygnet, compared to the Cd 0.40, 1964, Porsche 911. It's all about the aft-body.
