Quote:
Originally Posted by JulianEdgar
Yes, as I already said, it's possible to dream up a situation where a roof spoiler creates lift. (You seem to have missed the part about it being a roof spoiler.) But as I also said, with any modern car with attached flow on the rear window (and the quoted book shows a sedan) then it's extremely unlikely. And it's certainly not common.
So a good example of Aerohead writing material that is not relevant as he seems to be talking about a boot spoiler, not the roof spoiler that's under discussion.
If Aerohead is arguing it, black is white and white is black. A wing is not a spoiler, and a spoiler is not a wing. If Aerohead believes they are different only semantically, that's fine - another example of a misleading post from him.
Again, a typical misleading Aerohead statement - he just loves misquoting what others write. I didn't just say: 'most lift comes from attached flow', I said:
It's highly unlikely that any spoiler will create lift on any modern car (where most lift comes from attached flow), unless something really weird is done so that the spoiler deflects air massively downwards.
Note my specific reference to modern cars: and yes, in modern cars, where there is attached flow over the upper surfaces, most lift does in fact come from attached flow.
An aircraft wing is a streamlined body with attached flow - yet it generates no lift? Dear me - yet another wrong statement from Aerohead. (I think we've been here before, and if I remember correctly, Aerohead then had his own definition of what a streamlined body comprises.)
I don't think so. I've now had chapter by chapter feedback on the book from:
- the head of Jaguar Land Rover aerodynamics
- an ex-Tesla aerodynamicist
- the head of Porsche aerodynamics
- a professor of aerospace engineering and author of two books on car aero
- a Formula 1 aerodynamicist
...not to mention of course feedback from the tech consultant when I wrote the book, who happens to be a world-renowned aerodynamicist.
None of them suggest any mistakes about 'wrapped flow' and 'lift'.
And you know what, I think I'd trust their opinions over Aerohead's ideas.... |
* I was addressing the ability of a decklid spoiler to slow the air down and increase pressure.
* Anything that spoils lift is a 'spoiler'. Wings included.
* I'm in disagreement with your broad-brush assertion that, with modern cars, that 'most lift comes from attached flow.'
*It's my opinion that, caveats/ conditions need to be spelled out.
* If you have an industry-wide statistical analysis which demonstrates that for the entire vehicle population, that causality of lift is directly associated with a statistically significant proportion of vehicles, only then could one make such an argument.
* And just for the benefit of the reader, allow that there are exceptions to your general claim.
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* If you're only testing vehicles possessing contour-compromised roofline profiles, which violate the ' ground rules of fluid mechanics' as Hucho refers to them, all your data will suggest that presumed attached flow is responsible for lift. An inescapable intellectual cul -de -sac.
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* Wing sections are not streamline bodies, in the strict sense of the term. Wings operate in two-dimensional flow. As mentioned elsewhere, every wing profile has an angle-of-attack at which zero-lift is achieved. In the back of their book, Abbott and Von Doenhoff provided tables for all extant wing profiles, and the tables provide dedicated columns just for the zero-lift data.
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* 'Streamline bodies' denote 'streamline bodies of revolution', and for automotive application, ' half-bodies of revolution.' This is technical language specific to road vehicle aerodynamics.
* The 'aerodynamic streamlining template' is based upon a half-body, derived from a streamline body of Cd 0.04, the drag minimum known, for a body of which the aft-body contraction contour does not exceed 22-degrees as measured off a horizontal projection.
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As I was not a witness to your communications with your team of aerodynamicists, I've no idea about the specific language chosen in your exchanges which would lead to your conclusions.
Your choice of 'wrapped airflow' is a very unfortunate choice of wording, it is not a 'technical' term used in the profession, and extremely problematic with respect the reader experience.
Not everyone excels at technical writing.