Quote:
Originally Posted by Vman455
1) cD is based on frontal area only for convenience' sake. We could relate cD to plan area, as in aeronautics, or wetted area, or any other reference area we choose. However, those are all much harder to measure or calculate on complex three-dimensional bodies such as cars.
6) "Scaling factor" in aeronautics and aerodynamics refers to the necessity of obtaining the same Re in the flow around a model as the full-size object, as in this paper written by some researchers working down the street from me. It appears you are conflating "scaling factor" with "fineness ratio," as freebeard suggested. But, since production and concept cars have widely varying fineness ratios this isn't an accurate method of predicting Re for cars based on height or frontal area, as I pointed out in a post above. (It might work for 18-wheelers, which have standardized trailer lengths, typically 53'). |
1) Frontal area-based drag coefficient has been the industry standard basically all along.
2) I don't mention 'aeronautics' just as I never mentioned 'aerodynamics' with respect to static 'lift'. Please read for comprehension and pay close attention to actual language!
3) Any 'profile' will be profoundly affected by fineness-ratio. Any given frontal area demands a matching length to preserve the fineness ratio.
4) For road vehicle aerodynamics, scaling-factor has to do with dynamic similarity, verisimilitude, precisely related to Reynolds number. It's an absolute necessity with respect to scale-model wind tunnel testing.
5) I don't 'conflate.' The science speaks for itself.
6) A 'life-size' automobile, above 20-mph, will be at super-critical Reynolds number, and constant drag coefficient up to transonic velocity.
7) We don't need to concern ourselves with RN effects of a 'real' car.
8) The context of modern 'competition laminar' bodies is exactly related to frontal area, as it undergirds every other dimension of the body architecture.
One cannot understand the 'context' of a 'laminar' body without this understanding.
That was the condition of the discussion.