Quote:
Originally Posted by kach22i
The author neglects to mention these new sharp front corners are feeding Air-Curtains for the front wheels and the pressure is being redirected. This lack of understanding and attempt to tie it into other things such as minimum radius on the Ford Flex concept (actually called 2005 Ford Fairlane Concept) leads to some distorted assumptions and conclusions in my opinion.
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Keep in mind, this article was written in 2009--three years before the first air curtains appeared on a production car.
The most egregious line is the last, in my opinion: "Still, the wind tunnel continues to bring new discoveries. 'Aero,' said Michael Simcoe, a veteran exterior designer at GM, 'remains a black art.'" To contrast, here's an excerpt from W.H. Hucho's keynote paper delivered at the 1976 GM conference on aerodynamic drag:
"As has been shown, most of the knowledge in vehicle aerodynamics is qualitative in nature. Some attempts to transfer results from other fields of aerodynamics to the flow around cars have been quite successful. Nevertheless, what can be deduced from them is guided empiricism rather than systematic design procedures. Unlike other disciplines of fluid dynamics, as for instance turbomachinery or aeronautics, little quantitative information is available on which a rational design procedure for road vehicles can be based.
"What is needed first is a complete picture of the flow field surrounding a car. The various flow modules have to be identified, and their contributions to drag elaborated. The only way to do this is by experiment, and appropriate techniques are available. However, in order to generate complete understanding and to develop design procedures which will convert aerodynamics from an art to a subject of rational engineering, the experiments have to be supported by theory.
"In the course of this Symposium it will be indicated what can be expected from the application of fundamental theoretical flow models, namely: potential flow, boundary layer theory, wake flows and vortex flow-fields. Despite the fact that a complete theoretical model can not be expected in the near future, this theoretical penetration of the subject is not meaningless. Theory must serve to both guide and interpret the experiments. This should bring a better understanding of the flow around cars. This deeper understanding would be of great help in solving the problems related to all four categories of vehicle aerodynamics outlined in Fig. 2 [performance, stability; flow field in detail; engine cooling; heating, ventilating]." (Hucho, W.H. "The Aerodynamic Drag of Cars: Current Understanding, Unresolved Problems, and Future Prospects." In
Aerodynamic Drag Mechanisms of Bluff Bodies and Road Vehicles, Sovran, G., Morel, T., and Mason, W., ed., [New York: Plenum Press, 1978], 37)
The publication of books such as Hucho's own
Aerodynamics of Road Vehicles in 1987 and the advent of computer simulation have changed ground vehicle aerodynamic engineering, yet designers such as Simcoe still believe it's some sort of magic or intuition. The major problem is still, as is hinted in the article, that these designers get to decide the "look" of a car and then aerodynamic engineers have to make it work without changing that look significantly (as we saw with the Volt, which was still compromised aerodynamically compared to its competitors such as the Prius). It should be the other way around. How much of the Cybertruck's steampunk look was decided on before aerodynamic efficiency was considered, I wonder?