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Old 01-25-2024, 11:14 AM   #5 (permalink)
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' flat vs up '

Originally Posted by Phase View Post
So flat horizontal spoiler, low drag. Up spoiler, more downforce
I've never seen a definitive research published, in which a 'flat' rear spoiler was shown to be of superior performance to an 'angled' spoiler, as far as low drag was concerned.
Perhaps someone will do that sometime.
As far as I know, as long as the tearing edge of the spoiler is positioned at the 'reversal point', where the boundary-layer has reattached, and pressure recovery resumed, we're essentially 'done' with the streamlining portion.
If the tearing edge is then pushed further upwards, the streamlines will be over-constricted, more closely-spaced, increasing their velocity, lowering the static pressure, creating a larger wake, of lower base pressure, increasing pressure drag, increasing total drag, exactly the opposite of the kind of 'aerodynamics' Dr. Hucho sought to teach us about.
And a challenge for us is, recognizing 'false attachment' of downwash when we experience it, compared to actual attached flow.
Tuft testing can easily deceive the experimenter, and pressure readings are meaningless without some reference to a 'target' pressure profile known to be associated with the streamline flow of minimum drag.
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