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Old 07-07-2022, 03:37 PM   #6 (permalink)
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roof attachment

Originally Posted by kach22i View Post
I wonder if a roof form was just shy of having air attachment if raising the rear or lowering the front would cause improved attachment and lower the Cd.

Rake angle affects the top surface as well as the undercarriage plane is all I'm saying.

If the Audi A2 has complete roof attachment then its results may be for that car only?

Complete roof attachment is sadly rare, just say'n.

It's hard to tell. The camera vantage point is 'low' and 'forwards' alongside the body. One can't actually observe the lowest streamline smoke filament in relation to the spoiler.
I have a blueprint, and the roofline IS a bit aggressive in its contour.
The Euro-spec A2 was Cd 0.25 according to Robert Cumberford, designer, and contributor to AUTOMOBILE Magazine.
Smoke on BIONIC Boxfish looks like it's trying to take the paint off the car. It happens to fit the AST, so that would not be surprising.
If A2 was a bit too steep, a weak counter-rotating vortex pair could be inducing a touch of downwash which would otherwise appear like 'attached' flow.
The EPA says ' Local declination should be within 3-5 degrees of streamline locally... no slant perturbation beyond 4-degrees ... smooth, continuous.'
A2 probably satisfies that.
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