Quote:
Originally Posted by aerohead
* 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.
|
What Aerohead said on 12/5/2020:
Quote:
Originally Posted by aerohead
* I believe that the lift issues that you believe to be the major reason for rear lift would actually be attributed to separated flow over a horizontal portion of the aft-body, ahead of the transom. Squarebacks are incapable of generating rear lift.
*The Cayenne and I-Pace both will create this separation with, zero chance of re-attachment, as they violate the limits of the Mair/Buchheim departure slope angles, necessary to allow for re-attachment.The plan-view section of the roof exposed to the turbulence is at the lowest static pressure, compared to the suction peak at the windshield header,and this low, acting over the 'lever arm 'spanning the distance to the tail creates the 'moment' which lifts the tail. Simply extending the roof to the back of the vehicle cancels the moment, leaving a higher base pressure, and lower pressure drag.
|
You can be confident that there is no separation at all on the roof of the Cayenne - this is just two versions of Aerohead's weird theories of lift on squarebacks. (Or, if you want to overlook the inconsistencies - no lift on squarebacks.)
Or is Aerohead actually trying to say that lift is caused by the wake pressure acting on the angled rear glass? (It's so hard to understand when he writes in such an obscure style - what is a transom? I didn't know the Cayenne was a boat.)
Either way, the theories are wrong, as I explained in detail in the original post.