Quote:
Originally Posted by AeroMcAeroFace
Surely aerohead, it would be better to argue from the point of drag, downwash induced attached flow will be almost always higher drag than if the flow were "real" attached flow. Or reattached flow is almost always higher drag than if it was attached flow.
Arguing that the flow isn't attached and the tufts are lying and every expert is wrong seems difficult to believe. Saying that you have a different definition of attached flow seems far more reasonable to me.
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* Exactly! Which Hucho succeeds with.
* Vortex-drag is of the highest drag.
* A too-radical profile may produce a small wake due to downwash, however, the wake itself is of very low pressure, creating a low base pressure, high pressure drag, and high overall drag, in addition to the long-lived, drag-producing vortices themselves, which cannot possibly offer any constructive pressure regain.
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If the flow were actually 'attached' the TBL would be intact. The local streamline just outside the TBL would be imparting higher and higher pressure, the further rearwards on the body, all the way to the trailing edges.
If separation occurs, the pressure of that above the separation line, is transmitted throughout the entire region of separated flow. All the way into the wake unless there's a physical boundary to prevent it.
This is part of the reason a Mitsubishi Mirage 'G' model is Cd 0.27, whereas, a Porsche Macan is Cd 0.37. The mutilation of the Porsche roofline is robbing the ability of pressure regain over the segment cut away from the roofline. ( Exactly what Kamm studied at his FKFS).
There's a reason why the professional language differentiates between ' attached' and 'downwash' flow. They are completely different animals.