Quote:
Originally Posted by JulianEdgar
The discussion was about roof spoilers, so as usual, Aerohead's post (which as about boot spoilers) just sows confusion.
A wing is not a spoiler, and a spoiler is not a wing, in any technical automotive use of the words. I am glad Aerohead reiterates his misconception so that can be no confusion in the minds of people reading this that his mistake was just a typo.
I am quite happy to stand by my point that most lift on modern cars comes from attached flow. Just look at any CFD image or wool tuft / pressure testing of any modern car shape. There are plenty around to look at!
So far we have discovered that, according to Aerohead, wool tuft testing cannot be trusted, smoke testing doesn't show what it is supposed to - and now, pressure testing is invalid as well. No doubt subsequently we will get to the invalidity of measuring overall lift. Most people would find it pretty hard to maintain a theory when all the quantitative evidence is against it, but not Aerohead.
I am glad Aerohead reiterates his misconception that a wing is not streamlined; then there can be no confusion in the minds of people reading this that his mistake was just a typo. As I have previously said, Aerohead has his own definition of 'streamlined' - one that doesn't match any normal technical automotive use.
So Aerohead has said before. But, with respect, so what? It's his theoretical hobbyhorse, but it is one that is basically ignored (1 -2 pages max in a whole book, if that) by all the current major authoritative texts on automotive aerodynamics. Why do they ignore it? Because it's of such little significance.
Aerohead is certainly right about that.
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I'll repeat from what I posted many months ago. Julian is a 'writer.' I'm uncertain that he's a 'reader.'
1)'[L]ow drag can only be achieved when the separation at the rear is eliminated.' Hucho, 2nd-Ed. page 16 ( template)
2)' [T]he optimum shape in terms of drag is a half-body, which forms a complete body of revolution together with its mirror image- produced through reflection from the roadway.' ( template) Hucho, page 15.
3) ' [T]he value of Cd 0.15 can be realized with more than one single body shape.' Hucho pg 201
4) ' Lower drag can only be achieved by extending the length of the vehicle's body.' Hucho pg 201
5) ' The drag coefficient for...passenger cars may be plotted against vehicle length.[I]f the evaluation is limited to vehicles that were developed for the lowest possible drag coefficient ( template ),( the correlation discerned between greater lengths and lower drag ) this expected trend in in fact confirmed.' Hucho pg 202
6)' A closer approach to the value of the basic body without wheels ( Cd 0.07 - Cd 0.09 ) is only achievable through further integration of the wheels into the body.' ( template ) Hucho, page 201
7) ' The drag and lift of a body depend strongly upon the angle of attack.'
Hucho, pg 202, Re Stollery & Burns, Ref. 4.82 ( bodies of revolution / template)
8) ' It is very unfortunate that numerous ( lift ) investigations on basic bodies are inconsistent.' Hucho, pg 205 ( bodies of revolution )
9) ' A more systematic investigation is needed to generate the basic knowledge on the aerodynamics of bluff bodies close to the ground.' Hucho, pg 206 ( bodies of revolution / template )