Aerodynamics thread

Discussion in 'Air Force' started by siegecrossbow, Mar 12, 2012.

  1. Tirdent
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    Tirdent Junior Member
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    It may be pertinent to point out at this juncture that the paper talks about max lift coefficient, NOT max L/D (which would indeed be contrary to fluid dynamics). Vortex lift is seriously draggy, but offers the possibility of improving lift at AoA where a conventional wing would already be stalled - the drag is taken care of by high T/W ratio. As the paper mentions, the low aspect ratio is also beneficial to supersonic drag thanks to improved longitudinal distribution of cross sectional area and low t/c ratio.
     
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  2. Tirdent
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    Tirdent Junior Member
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    To change the flight path of the aircraft, you need to generate a force in the desired direction. The bigger this force, the faster the aircraft will change direction. On a typical aircraft configuration, the aerodynamic surfaces capable of generating by far the largest lift force are the wings, so the best approach to a hard turn is to bank and point the wing lift vector where you intend to go. You're never going to fly a 9g turn with the lift created by the fuselage sides in side slip (never mind that you'd probably snap the pilot's neck, if you did!).
     
  3. latenlazy
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    latenlazy Colonel

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    I never chased these figures down before, so doing the lazy thing and asking, but do you know how drag induced from vortices compare to drag from increasing the wing’s aspect ratio?
     
    #1123 latenlazy, Apr 11, 2019
    Last edited: Apr 11, 2019
  4. Tirdent
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    Tirdent Junior Member
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    That's too broad a question because it comes down to design priorities. For the purpose of low speed turning at AoA > 20° you aren't exactly spoilt for choices - it's either vortex lift or none at all (and a high aspect ratio wing able to survive the buffet loads may well be weight prohibitive). For best subsonic loiter or range at 1g, high aspect ratio will decrease drag, hence airliner wings and VG on some fighters which strongly emphasize patrol endurance.
     
  5. latenlazy
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    latenlazy Colonel

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    I was being broad on purpose here. Of course the answer will vary based on flight regime, *but* that’s also why lift and drag curves are often defined as relationships across a range of flight conditions. I was mostly curious about what those relationships looked like, in comparison to each other, across different flight regimes.
     
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