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I Vortex Lift

  1. Mar 14, 2016 #1
    For an airplane, their are multiple types of lift, camber, angle of attack, pressure difference, and vortex lift.

    I understand that at the end of wings the low pressure at the top, and high pressure on the bottom causes their to be a vortex formed. My question is, how exactly do they use that vortex for lift?

    I believe that they have wings with extremely high aspect ratios, so that the entire wing can be treated as a wing tip (or atleast I think so). so how do they use that vortex for lift?

    Thank You, your help is much appreciated.
     
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  3. Mar 15, 2016 #2

    Nidum

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  4. Mar 15, 2016 #3

    FactChecker

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    It is really better to say that there is only one type of lift, and it is from pressure difference. The causes of pressure difference can include camber and angle of attack. Vortices are an indicator of pressure differences and go hand-in-hand with it. It is true that the speed of air in a vortex makes it less effective in increasing the pressure on top.

    If there is low pressure at the top and high pressure at the bottom, then there is lift. The vortex just goes hand-in-hand with that pressure difference. Air gets drawn in by the pressure difference and forms a vortex, so it is just an indicator of the pressure difference.

    It is really the opposite. A very high aspect ratio means that the wing tips are a small part of the equation. So the higher the aspect ratio, the less the wing can be treated as a wing tip.
     
  5. Mar 15, 2016 #4
    Ok, so how do they get lift from the vortexs that form?
     
  6. Mar 15, 2016 #5

    boneh3ad

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    Wingtip vortices are actually usually harmful to wings, not beneficial. This is why you see winglets and other wingtip devices on most planes these days.

    At any rate, the wing doesn't just "get lift from the vortices." The vortices are one part of a more complex flow field that, as a whole, determines the lift on a wing. Subsonic air flow, in general, is not linear and is not a situation where superposition holds without certain simplifying assumptions. If you simply remove the vortices from the picture, you've fundamentally altered the flow field and it doesn't work.
     
  7. Mar 15, 2016 #6
    Delta wings use the votexs, and direct them over the wing, to create a low pressure system. What I am wondering is how it is directed over the wing?
     
  8. Mar 15, 2016 #7

    boneh3ad

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    You are talking about the leading edge vortex that forms on delta wings? That's a different story. That is unrelated to the wingtip vortices you cited in your original post. The vortices at the leading edge of a delta wing form due to boundary-layer separation at the leading edge and they get "trapped" there by the air flowing over the top of them and reattaching to the wing behind them. They increase lift essentially because they accelerate the air more than the wing otherwise would and therefore lower the pressure in that region. They also increase drag fairly substantially, which is why delta wings are inefficient at low speeds.
     
  9. Mar 15, 2016 #8
    So how is it that the leading edge vortex stocks to the top of the wing?

    Thank you all, you all are super helpful
     
  10. Mar 15, 2016 #9

    boneh3ad

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    Like I said, it originates there as a result of leading edge boundary-layer separation and stays there because the air traveling over the top of it essentially wraps back around and reattached to the wing behind it. It's kind of like it is held there in a little pocket.
     
  11. Mar 15, 2016 #10
    This is a neat website I discovered years ago about vortex lift. It provides a cool introduction into the subject and some nice figures too.

    http://www.acsol.net/~nmasters/vortex-lift/ [Broken]
     
    Last edited by a moderator: May 7, 2017
  12. Mar 15, 2016 #11

    rcgldr

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    If I recall correctly, for a delta wing, the leading edge vortices flow somewhat outwards along the leading edge as well as backwards across the wing. The AOA of attack for stall on a delta wing is around 20º, much greater than a conventional wing.
     
  13. Mar 17, 2016 #12
    Thank you, Thank you all Very much for all of your help
     
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