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How wings generate lift?

  1. Sep 25, 2015 #1
    Wings generate lift because of the curved shape of the top wing air flow faster over the top and sucked up the plane. This would be bad for a fighter jet flying upside down. Wright brothers plane wings are flat so the wing must be deflected down. So curved wings are just aerodynamic. Soo which is correct?
     
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  3. Sep 25, 2015 #2

    jbriggs444

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    Which of what is correct? What two contradictory statements do you see?
     
  4. Sep 25, 2015 #3
    Curved wings produce lift or air deflection do everything as flaps the deflection of air.
     
  5. Sep 25, 2015 #4

    jbriggs444

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    How are those statements contradictory?
     
  6. Sep 25, 2015 #5
    If curved wings produce lift, you cant fly upside down. If flat wings are better why so many curved wings?
     
  7. Sep 25, 2015 #6

    jbriggs444

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    Curved wings do produce lift and you can fly upside down. What leads you to think differently?
    Because "better" depends on your requirements. What is better for fighter jets may not be better for commercial airliners or for paper planes.
     
  8. Sep 25, 2015 #7

    russ_watters

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    The airfoil of the Wright Flyers was most certainly not flat. Identifying the optimum curvature was one of their major innovations.

    As others said, what is optimum depends on the requirements. But it is noteworthy that by increasing the angle of attack you can make a surface that curves up (the underside of a wing) direct air down.
     
  9. Sep 25, 2015 #8

    Nidum

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    Some aircraft designed specifically for aerobatics have symmetrical wing profiles .
     
  10. Sep 25, 2015 #9

    CWatters

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    That's not correct. The angle of attract and the shape of the wing both contribute to the production of lift. A flat plate can generate lift if given an angle of attack. Some curved wing sections can generate lift with zero angle of attack or even a negative angle of attack.
     
  11. Sep 25, 2015 #10

    cjl

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    Yes, and even aircraft with asymmetrical airfoils can fly upside down - they just need to use a much larger angle of attack to do so than they need when flying normally.
     
  12. Sep 25, 2015 #11
    Ok after some research, I got it. Thanks everyone
     
  13. Sep 26, 2015 #12
    Good job Neon. It is relaxing to hear just that. I have witnesses some horrific aftermath from aircraft crashes and they are almost always pilot error. Like John Kennedy and hundreds more. They were up and did not fully understand what can happen and how to get out of a lethal situation.
    Again great job NEON. If you become an aviator, know every aspect of the aerodynamics and the physics behind it and you will have a great and wonderful and long life enjoying the freedom of the skies.
     
  14. Sep 26, 2015 #13
    The phenomenon of lift can be explained in its entirety using Isaac Newton's 2nd and 3rd law. The blades/wings have a huge forward momentum and exact force on the air. As a result, the air is deflected in a slightly downward direction. Bringing in the Newton's 3rd law, this deflection 'air stream' caused by the wing will provide a net upward force on the wing, which is termed as lift.
    No matter what, the air stream HAS to be deflected downwards. You can induce this deflection through a non-symmetric airfoil with or without an angle of attack, or a symmetric one with an angle of attack.
    There are other subsidiary effects which make the airflow to 'stick' to the profile of the wing. One should look up Coanda effect. It explains why a person standing next to a charging train is pushed into the train.
    For a particular velocity, a higher angle of attack means higher lift only until a certain angle. After that, the effects like flow separation and turbulence come into picture.
     
  15. Sep 26, 2015 #14

    boneh3ad

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    The Coanda effect pertains most correctly to a fluid jet adhering to a surface, not the flow over an object such as a wing like you cite. The air "sticks" to a wing due to viscosity and the simpl fact that if it didn't stay near the surface, there would be a vacuum, which obviously can't happen.

    This is also not why a person would tend to get drawn toward a passing train. In fact, in general that doesn't happen near the sides anyway. The real danger of that is right after the train passes and air tends to rush into the low-pressure wake.

    Flow separation and therefore stall causes the effect you cite. Turbulence can occur at any angle of attack, however. In fact, in most situations, the majority of the flow over a wing is turbulent.
     
  16. Sep 26, 2015 #15

    sophiecentaur

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    Yes, this is something that some Bernouli enthusiasts will argue against, vehemently, on the grounds that Bernouli is 'enough' of an explanation. But there absolutely has to be a vertical force and that can only be caused by a continuous process of changing momentum of some air, possibly quite distant from the wing. To see this downward flow of air, it's no good going into a wind tunnel (the argument commonly used) because a wind tunnel has that vertical force directed at its bottom half and such an experiment only shows the amount of lift force but does not 'explain' it. The wing will effect the region of air in the immediate vicinity and Bernouli works in the near region but you need to look outside this region to get the downdraft effect. I make that statement on the grounds of faith in Newton's laws and not as result of any fluid dynamics argument. But Newton is ultimately in charge of all these situations The downwards force reveals itself impressively in the wake of a large jet aircraft which is a region of lethal downdrafts. .
     
  17. Sep 26, 2015 #16

    DaveC426913

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    By this logic then, as long as you provide an angle of attack, a flat slab of a wing with no curve and no asymmetry would get jut as much lift as a modern cambered wing.
    Yet such is not the case.
     
  18. Sep 26, 2015 #17

    boneh3ad

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    The logic you cite makes no such claims. It only claims that a flat slab will generate lift provided it has nonzero angle of attack. It makes no claims about the amount of lift relative to an actual airfoil. In fact, this is why we have airfoils, as they operate much more efficiently at subsonic speeds.
     
  19. Sep 26, 2015 #18

    DaveC426913

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    i.e., he is claiming there is no other component.
     
  20. Sep 26, 2015 #19

    sophiecentaur

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    Is this not ultimately affected by Drag? If you pull a flat plate through the air on a bar, you can get deflection force at all angles. It would just be a lunatic design for a wing to have such a steep attack angle.
     
  21. Sep 26, 2015 #20
    I think BreakingBaDude meant that you could have a working wing without the necessity of the aerofoil profile.
    A completely flat winged plane COULD fly as long as the wing has an angle of attack.
    It would be very inefficient and would waste a lot of energy as unnecessary drag, but it could actually fly.
    In fact I know it can, A Iong time ago I made catapult launched balsawood models with flat wings (delta wings too!), and yes they worked.
    They just didn't stay airborne very long, but they flew alright .. and they looked cool too:cool:.
     
    Last edited: Sep 26, 2015
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