1. Trailblazer

    Trailblazer Senior Member

    Hope this is OK to post here - it's quite a new video and one I hadn't seen before - a really good compilation of low-altitude vortices and aerodynamic contrails on take-off and landing.

    Look at 5:12 for a nice propeller contrail from a Flybe Dash 8 :)

     
    • Like Like x 3
  2. cloudspotter

    cloudspotter Senior Member

    Interesting effect here [Optical effect, Starting 4:00]

    vortex.JPG
     
    Last edited by a moderator: Dec 3, 2014
  3. Trailblazer

    Trailblazer Senior Member

    I think that is the vortex being spread outwards as it interacts with the ground?
     
  4. cloudspotter

    cloudspotter Senior Member

    Sorry, I meant the distortion of the lights and lines viewed through the vortex
     
  5. Mick West

    Mick West Administrator Staff Member

    Fascinating. It's the pressure gradients within the vortex bending the light. An extreme and oddly shaped version of the hot air mirage. It's exaggerated by the perspective foreshortening.
    [​IMG]
     
  6. Trailblazer

    Trailblazer Senior Member

    Oh, yeah. That's pretty cool. The refractive index of air varies according to temperature, pressure and water vapour content. I'm not sure which would be the dominant factor here though...

    Edit: Mick beat me to the post. Probably pressure, then?
     
    • Agree Agree x 1
  7. cloudspotter

    cloudspotter Senior Member

    Figured it was along those lines but the foreshortening hadn't occurred to me
     
  8. Mick West

    Mick West Administrator Staff Member

    It's really the density (mass per unit volume), which is kind of the same thing here.

    Similar principle to seeing an explosion shock wave. (see various views from 2:05 here)


     
    • Like Like x 2
  9. MikeC

    MikeC Senior Member

    Plus some wingtip vortices - check out the opening shot - spot the "contrail" inside the intake of the port engine - never seen that before!! :)

     
    • Like Like x 2
  10. Mick West

    Mick West Administrator Staff Member

    It makes sense though, at low speeds the air is being vigorously sucked into the engines, which would create an area of low pressure just in front of the intake blades.

    And I think it's the same on both engines, just one is in shadow.
     
    • Agree Agree x 1
  11. MikeC

    MikeC Senior Member

    Could be - there are flickers on the stbd engine....