10 ms·

For anyone interested, there are several great youtube videos[1-4] that show the wakes (the wingtip vortices in particular) created by various aircraft. This i

• csours 10y ago
  Those wingtip and flap effects on 2 are gnarly! I assume that those occur near dewpoint? or some other atmospheric conditions?
  • jacquesm 10y ago
    They always occur. It's just that around the dewpoint you can visualize them. But they're all the more deadly for normally being invisible.
  • phumbe 10y ago
    To add to jacquesm's response, the footage in [2] is definitely from a humid day. That makes condensation happen very readily. If I remember correctly, the trails from the outboard edges of the flaps are just like wingtip vortices. The airfoil's geometry suddenly changes, acting like a wingtip and creating a vortex.
  • cyberferret 10y ago
    If you recall Boyle's Law from high school physics - Temperature is proportional to pressure. Aircraft wings generate an intense area of low pressure over the top of the wing (which is what essentially generates the lift). This low pressure area is magnified when flaps and slats are deployed. On a humid day, the lowering of the pressure over the wings can basically force the air temperature at that point to lower and reach dew point temperature, essentially forming temporary clouds that are whipped around by the moving air vortices. Once the aircraft has passed that point, the temperature generally stabilises and conforms to surrounding air temperature, which usually dissipates the temporary condensation. The 'twirly' bits on the wingtips is basically spillover from the high pressure under the wings to the low pressure above the wings, creating that mini tornado vortex. This is also the reason that many modern aircraft have those 'winglets' on the wingtips, to try and minimise these spillover vortices which can cause problems for trailing aircraft, as well as induce extra drag on the source aircraft.
    • Zak 10y ago
      Wings generate lift primarily by deflecting air downward. There is an area of low pressure over the wing where air is taking a longer path than under the wing, but that is only responsible for a small fraction of the lift.
      • nether 10y ago
        "Longer path" has no bearing on reality. A flat plate can generate plenty of lift even with both sides the same. It's also hard to define "path," as the air starts convecting well ahead of the wing in subsonic flow.
        • hexane360 10y ago
          Additionally, the paths don't meet up/join at the trailing edge of the wing. There's no reason air above and below needs to separate and meet up into the same flow.
        • xelxebar 10y ago
          While you're on point about flat wings, in wind tunnel tests on profiled wings, you do in fact see a velocity difference between top flowing and bottom flowing streams. It's not enough of a difference, however, to cause coincident streams on the leading edge to line back up at the trailing edge.
        • teapot01 10y ago
          NASA has even published on this issue https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html
        • ajross 10y ago
          Flat plates generate lift even in near vacuum conditions where the whole idea of Bernoulli flow is inapplicable, even.
        • simion314 10y ago
          If I remember right the "longer path" thing was in Encarta, there was a guy that used Encarta to prove to me that the theory is right and I believed it m it made sense I am wrong and not the encyclopedia.
• bbcbasic 10y ago
  [7] https://youtu.be/ZJ9uWsvR1l0?t=145 https://youtu.be/ZJ9uWsvR1l0?t=145
• ryguytilidie 10y ago
  Cool example of vortices on an F1 car as well: https://www.youtube.com/watch?v=ZlDnd3B1rhs https://www.youtube.com/watch?v=ZlDnd3B1rhs
  • knodi123 10y ago
    That looks like lens flare to my untrained eye. I would never have thought that was smoke in a vortex.
    • lisper 10y ago
      Nope, definitely a vortex. Lens flares don't curl like that. But it's not smoke, it's condensation caused by the reduced air pressure in the vortex. You can see similar condensation happening for the same reason (but without a vortex) behind the tire.
• mirimir 10y ago
  From #6: > In addition to mitigating en route midair collision hazard, SLOP is used to reduce the probability of high-altitude wake turbulence encounters. During periods of low wind velocity aloft, aircraft which are spaced 1000 feet vertically but pass directly overhead in opposite directions can generate wake turbulence which may cause either injury to passengers/crew or undue structural airframe stress. This hazard is an unintended consequence of RVSM vertical spacing reductions which are designed to increase allowable air traffic density. Rates of closure for typical jet aircraft at cruise speed routinely exceed 900 knots. Seriously, "unintended consequence"? It seems quite obvious in retrospect.
  • knodi123 10y ago
    unintended? of course! that's not the same as unexpected :-)
    • mirimir 10y ago
      Well, I can't imagine that it was unexpected. So perhaps it was an unavoidable trade-off. But to say "unintended" is extremely disingenuous.
• bglazer 10y ago
  Perhaps you should warn people that video number 4 is an aircraft accident that possibly shows people dying.
• smarx007 10y ago
  Reproduced on smaller planes: https://www.youtube.com/watch?v=KXlv16ETueU https://www.youtube.com/watch?v=KXlv16ETueU (from 0:46)
• mcguire 10y ago
  The last video, the DR400 vs the Antonov, is an excellent demonstration.