[Phase]

Originally Posted by aerohead

Nope!
* From Hucho, Janssen, and Emmelmann, SAE Paper # 760185, Page-15, Figure 27, we're instructed that a 'gap' can only trigger TBL separation, and only on a 'roof.'
* Tripping the flow 'ahead' of an 'adverse-positive-pressure-gradient-inducing roofline, prohibits the flow separation-induced downwash drag and lift which would otherwise develop, had the flow not been intentionally separated.
* With the 1st-gen Golf-Rabbit, simply taping the rear hatch gap on the roof, caused the drag to degrade from Cd 0.42, to Cd 0.48 ( 14% ), along with 28% increased rear lift, due to the counterrotating vortex pair, low pressure downwash vector 'above' the backlight, and small, low-pressure wake.
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* Any form of VG would have to 'protrude' into the TBL, rather than reside within some body recess.

Taping over the gap increase drag? I’m confused