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Old 05-27-2020, 11:38 AM   #10 (permalink)
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tuft images

Originally Posted by JulianEdgar View Post
Well, you could write lots of stuff that justifies your position on a purely theoretical basis - or you could just look at:
  • the tuft images from Porsche
  • the actual on-road measurements I have made.

Statements like "Which results in counterflow on the roof,moving forwards towards the windshield,rolling up into eddies,then turbulence,lifting off the roof as separation" are simply rubbish. No tuft testing shows flow separation on the roof on any modern car. None.

(But then a moment ago you explained away the Porsche tuft testing because it didn't match your theory. Those tufts were just an "illusion of 'attached flow'". Talk about mental gymnastics!)

Honestly, why don't you get away from the keyboard and measure some pressures and flows on real cars on real roads? You will very quickly find those measurements don't support your theory.

(You say you have my book. Look on page 80. More measured pressures that don't match your theory!)
*The tuft flow images cannot be trusted with respect to attached flow. Hucho explains why.
* If you'll ever investigate streamline bodies, you'll finally understand the conditionality of your argument.
*I don't have your book with me,but we could discuss your Jaguar XE:
- the roof-line is a little too fast for its relative length,with respect to the overall body length.
-the TBL is compromised because of this.
-Jaguar reflexed the camber,attempting to lengthen and raise the rear trailing edge of the car, and get it closer to inviscid flow to guarantee re-attachment,and stability.
- they could have just lofted the whole rear of the body, but the stylist might have slammed on the brakes,as Hucho has discussed (see spoiler development of the VW Scirocco).
* If you'll take a look at the Tata,Jaguar C-X75 of 2011, you'll notice that the designers chose the 'template' to end the body, guaranteeing flow attachment off the boot,and no need of a rear spoiler,just like ALPINE does. It's 'draggy' diffuser area will provide enough high-speed downforce.
* The 911 does not have attached flow beyond the cooling air intake. It has enormous,drag-inducing longitudinal vortices.
* If they'd simply lofted the rear contour out to the tip of the whale-tail they'd have had lower lift and drag (but it would have had violated the 911 'silhouette' expectations of the customer).
*Contemporary Porches have abandoned the early 911 contour altogether and are running closer to the 'template,' reserving the actual 'template' contour for Le Mans and such, when aerodynamics really makes a difference.
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