Quote:
Originally Posted by JulianEdgar
I actually don't think people get it.
I used to wait after Aerohead posted something that was completely wrong - wait for someone to say "No, that's not right", but what people would do was to instead thank him for being misled!
A classic example: Aerohead saying that on the current Porsche Cayenne, the airflow separates at the top of the windscreen and is separated right across the roof. Absolute garbage - which if accepted, is going to lead people astray in almost any aerodynamic car modification that they might try to subsequently think-through on a squareback car.
And there are so many of his posts like that...
When I first came here, I couldn't believe some of the weird things people believed about car aero. And what really gobsmacked me was that they were said with an air of absolute certainty. I knew they couldn't have come from any formal references (textbooks or SAE papers) so I started to look at where they did come from. In nearly every case, they came from what Aerohead was spouting.
I initially tried correcting him (eg look at the Tesla paper on wheel design and don't keep saying that full wheel covers are always best for low drag), but instead of gratefully updating his knowledge, he just poured shXX on Tesla! I couldn't believe it! Then I realised Aerohead isn't really interested in getting correct information out to other posters; he's interested in repeating - ad nauseum - his old misunderstandings.
But as I often say - don't believe me! Go and read the Tesla paper for yourself. Go and put some tufts on a Cayenne. Read some good aero books - like the one this thread was originally about.
As Vman455 has found, as soon as you start looking at the references Aerohead quotes, reading some aero texts and doing some testing, you will quickly find out for yourself that Aerohead writes a great deal of misleading rubbish.
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* That's a rather remarkable observation. I have no recollection of ever saying such a thing.
I do recall making an association to lift with an attribution to the mutilation of the roofline, where the raked-roof truncation occurs. As the separation line is artificially moved closer to the suction peak by the stylist, the pressure is lower than if the roofline simply continued all the way to the rear of the body ( more like a RAV4 ), and since this lower static pressure is occurring 'over' the rear of the body, it's inducing lift. The separation creates turbulence which is incapable of transmitting momentum downwards, and with no reattachment, the wake gets dosed with lower pressure, which lowers base pressure, raising pressure drag, exactly what Hucho said we should avoid.
* I have the Tesla road test data from Germany. There's some context which is not addressed in their presentation. As is also true for the WS12 Aerodynamic Performance paper by Cranfield University et al..
* And again, if ventilated wheels are categorically, absolutely, with no reservation, superior to MOON, convex discs, why do automakers like Ford, General Motors, and Volkswagen choose them for land speed record attempts if their 'ventilated' wheels could clearly mean the difference in a world record? I believe that this is a fair question.
* If caveats and conditions exist, they need to be clearly addressed in any preamble to research findings.