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In general is a slat better than a vortex generator to delay flow separation, for high AoA or extremely curvature wing/objects?

Does this "roof vane spoiler" works same as slat at wing, because the position of vane is so far back compared to the slat and where it gets "new fresh air" like a real slat on a wing?

Can we use this vane so much back at some extremely high curve wing to delay stall?

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I doubt this vane can help to stay flow attached.

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    $\begingroup$ In what case? Are you asking about a car or a wing? How are the pictures you show applicable to your question? $\endgroup$
    – GdD
    Mar 23 at 9:57
  • $\begingroup$ He wants to know if VGs on the roof of the car ahead of the window would do the same job as those appendages. $\endgroup$
    – John K
    Mar 23 at 12:36
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    $\begingroup$ Of course they wouldn't. Vortex Generators don't look nearly as cool as a spoiler, so they wouldn't meet the requirement that the spoiler is fulfilling - looking impressive. $\endgroup$
    – Ralph J
    Mar 23 at 16:02
  • $\begingroup$ @RalphJ have you ever seen the row of VGs on the Mitsubishi Evo 7? They looked pretty dog-gone cool in a day when everyone else had "just" that little vane at the top of the rear window! $\endgroup$
    – FreeMan
    Mar 24 at 13:26

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On airplanes, slats are definitely more effective. A slatted wing's stalling AOA will go from 15-16 degrees to mid 20s.

VGs on the leading edge, if placed at the right spot (just forward of the laminar separation point at high AOA), will increase the stall AOA about half that, to somewhere around 20 degrees.

Problem is, those things on the cars aren't really slats, which have to go at the leading edge. Those are more properly called guide vanes, which are not quite the same thing, aerodynamically.

You'd want to see a wind tunnel smoke test to demonstrate that something is happening, and they are not just sitting in the already turbulent air doing nothing. Or you could stick some tufts to the back window and observe them as you drive with and without the vanes.

You would never put guide vanes like that on a wing though, as the drag they produce would far outweigh any benefit, and they may produce nasty stall characteristics.

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  • $\begingroup$ You think that vane dont work,just stlying? $\endgroup$
    – Jurgen M
    Mar 23 at 18:39
  • $\begingroup$ My hunch is it's mostly styling, or someone thinks it works but if you tested it maybe not so much, and for it to actually work it would need to be much larger. Tufts taped to the back window would show a pretty noticeable difference, so easy to test it out. $\endgroup$
    – John K
    Mar 23 at 18:45

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