I have a question on aeroalia's answer on this post (Why does the vortex created by wing affects its own angle of attack?).

If I'm not mistaken, wingtip vortices are generated behind the trailing edges of the wings and, even if we assume wingtip vortices somehow can reach the front area of the wings, it would only be able to affect the relative wind in front of the leading edge on the far outboard of the wings close to the wingtips, because after all it's wingtip vortices. Then, how could it be said that the upwash from the wingtip vortices changes the direction of the entire relative wind?


1 Answer 1


Please don't believe everything you read. You healthy scepticism is your best defense against the nonsense you might read about wingtip vortices.

What causes the flow to increase its angle when approaching the leading edge is the low pressure region above the wing. This is not only the main contributor to the wing's lift, but also the reason for the flow pattern ahead of the wing, in combination with the overpressure region around the stagnation point.

Please read this answer and let me know if something is left unclear.

  • $\begingroup$ Kampf So from the first link, I understand that wingtip vortices are actually the product from the entire trailing edge of the wing, not just from the wingtip. But I still don't get that how the low pressure above the wings works to push up the angle of the relative wind ahead of the leading edge. Even in an image given in your second link, the inflowing impulse stays horizontal while the outflowing impulse bends downward. $\endgroup$ Mar 5, 2017 at 23:25
  • $\begingroup$ @lemonincider: The suction above the wing works like the nozzle of a giant vacuum cleaner - why should it not suck in air from ahead and below? $\endgroup$ Mar 6, 2017 at 9:00
  • $\begingroup$ If that's the case, I mean, if the air ahead of the leading edge is sucked by vaccuum on the upper surface of the airfoil, shouldn't the relative wind ahead of the leading edge curve upward into and along the leading edge, not downward as described in this picture of the effective relative wind (en.wikipedia.org/wiki/Lift-induced_drag#/media/…)? $\endgroup$ Mar 6, 2017 at 9:54
  • $\begingroup$ @lemonincider Yes, it does. Don't look at silly graphics, better use real flow visualisation, like that classic here. There are even websites which explain things correctly. $\endgroup$ Mar 6, 2017 at 12:14
  • $\begingroup$ After reading the website you suggested, I studied the graphic harder and realized it's not really the depiction of the effective airflow ahead of the leading edge; it's just an extension of the effective relative wind behind the trailing edge. Thank you. $\endgroup$ Mar 6, 2017 at 19:13

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