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If winglets are added to an aircraft, do the vortices still interact with the airflow and create up wash and down wash. If the vortices do interact with the rest of the flow I am wondering how they do it.

So basically I am asking if wingtip vortices can affect airflow when there are winglets on an aircraft.

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Winglets do not change the laws of physics. In particular, they do not change the flow around a wing such that there is no up- or downwash. All they do is to involve a little more air into the creation of lift such that the vortex strength is slightly reduced.

With winglets, wingtip vortices now form at the tip of the winglet instead of at the wingtip. The wake behind the wing still rolls up and creates the usual wake vortices into which the wingtip vortices are absorbed. In order to create the same lift with a slightly less powerful vortex, the distance between both vortices is increased slightly. Actually, in order to support the winglet's weight, the aircraft needs to create slightly more lift with winglets than without, which reduces their benefit.

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  • $\begingroup$ So, the winglet causes vortices to occur further away from the wing which causes more air to be used for lift creation. $\endgroup$
    – Crafterguy
    Jun 23, 2017 at 13:20
  • $\begingroup$ @Crafterguy: Forget the vortices. The winglet allows to involve more air for lift creation. Therefore, more air is accelerated by less. $\endgroup$
    – Peter Kämpf
    Jun 23, 2017 at 14:41
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It depends what you mean by Wingtip Vortices. If you mean the ones from this answer, no amount of winglet will prevent them. These are the consequence of lift creation, and mainly influenced by weight and airspeed.

Strictly speaking, wingtip vortices are only the bit of air that flips around the tip of the wing. A very long winglet would prevent that, but a Cessna would still flop around mightily when it falls into the hole that the A380 wing left behind at approach speed. The wing tip is where lift creation ends, and there is a discontinuity there, winglet or not.

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Without winglets the wingtip vortices (or wake turbulence) stabilize at about two thirds of the wingspan. The closer the wake turbulence is to the planes body the more drag is induced.

Winglets virtually extend the wingspan (by a multiple of their own length) so that the wake turbulence stabilizes more distant from the body and thus the winglets reduce the induced drag.

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  • $\begingroup$ By "stabilize at about two thirds of the wing span", do you mean that the outer third of the wing span does not deflect air downwards? Is the situation you describe in cruise or in approach? $\endgroup$
    – Koyovis
    Jun 20, 2017 at 16:32
  • $\begingroup$ @Koyovis No. The center of the vortex moves from the wing tip towards the planes body aproximatly one third of the wing lenghs while the plane moves away. $\endgroup$
    – Timothy Truckle
    Jun 20, 2017 at 16:51
  • $\begingroup$ You might want to add that the multiple normally starts with 0. As in 0.3. $\endgroup$
    – Peter Kämpf
    Jun 20, 2017 at 16:51
  • $\begingroup$ @PeterKämpf When referencing the winglet length the multiple is bigger than 1, otherwise a longer wing would be more efficient. $\endgroup$
    – Timothy Truckle
    Jun 20, 2017 at 16:54
  • $\begingroup$ Nonono, check your data. A winglet is approximately as good as a span extension of 30% of the winglet span, given that the aircraft flies mostly at optimum L/D. $\endgroup$
    – Peter Kämpf
    Jun 20, 2017 at 17:04

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