1. Mick West

    Mick West Administrator Staff Member


    Source: https://www.youtube.com/watch?v=x1Fbyxlfxk4


    This thread is for posting close-up videos of contrails forming and evolving. It's just a general collection to help people who are interested look at exactly what is going on. It's also useful to have some high definition close-ups of phenomena that have described as "spraying" in the past - particularly full-wing aerodynamic contrails.

    The above video I took today around 7:40AM PST (15:40 UTC), it shows a plane leaving both aerodynamic and exhaust contrails. The interesting bit is in the first two seconds, where you see the aerodynamic contrail swirl around the exhaust contrail.

    Ideally add the info about the plane, but it's not required. This is Alaska 412, N546AS, a 737-890 at 35,000 feet.
    20161110-110901-kstq1.
     
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  2. Mick West

    Mick West Administrator Staff Member

  3. Trailspotter

    Trailspotter Senior Member

    Here is a video of hybrid contrails behind a B747 that I made a few weeks ago, but posted only today. In the beginning, I run the camera along the contrail from the plane to the end. When the aircraft was at the closest point, I kept camera at the same patch of the sky to record the contrail evolution from the moment of its formation until its decay by the Crow instability.

    Source: https://youtu.be/W-gAWkANqUg?t=30s
     
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  4. Trailspotter

    Trailspotter Senior Member

    Here is a repost of my post of July 19, 2016 from a different thread that contains a relevant close-up video.

    Source: https://www.youtube.com/watch?v=P3-IWfgsEeM

     
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  5. Dan Page

    Dan Page Active Member

    Fascinating, I never realized how much rotation there was with a contrail, you can definitely see it in your video, well done.
     
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  6. Trailspotter

    Trailspotter Senior Member

    A couple of contrail close-ups from today. Here it was a day of long contrails, which, however did not persist for long, except for a few local patches. The two following videos were taken five minutes apart.
    The first video pictures evolution of contrail left by an Embraer 170. Smaller than A320 or B737, this plane nevertheless create vortices capable of entraining a large fraction of the engine exhaust contrails. However, the resulting hybrid contrails seem to last shorter than those of heavy aircraft:

    Source: https://youtu.be/cqd6sJnQWN4


    The second one shows contrails of a rare aircraft, Boeing Dreamlifter, an extensively modified Boeing 747-400 for outsize cargo freight. The hybrid contrails of this aircraft were similar to B747 contrails in a previous post and lasted nearly twice as long as the Embraer 170 contrails, with their lifetime being limited by the Crow instability:

    Source: https://youtu.be/6zsEsYpZFUc
     
    Last edited: Nov 11, 2016
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  7. Trailspotter

    Trailspotter Senior Member

    Here is a close-up video of a short dissipating contrail that I took today:

    Source: https://www.youtube.com/watch?v=jMLv602-2JQ

    In the beginning, I was following the plane (Ryanair B737, flight FR1453 at 38,000 ft) for a while, then I hold the camera focussed on the same spot to record the contrail evolution. At this moment, another B737, G-JMCL, approaching our local airport at 4000 ft, entered the frame, making its engine exhaust visible on the background of the dissipating contrail:
    Screen Shot 2016-11-16 at 21.20.38.

    At the end I repeated the footage of the exhaust sliding along the contrail, having slowed it down ten times.
     
    Last edited: Nov 16, 2016
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  8. Trailspotter

    Trailspotter Senior Member

    Here is a video that I took in Lake District, England on August 10, 2016 at around 06:50 UTC. The Flybe Bombardier Dash 8 Q400, flight BE551, at 23,000 ft left a long persistent contrail "from the horizon to the horizon". A close up of the plane shows that the contrail was an aerodynamic one and had been triggered by the pressure drop at the propeller tips:

    Source: https://youtu.be/JaKBZLEBgK4

    I have slowed down the footage of the contrail formation behind the plane and its initial evolution.
    (With the hindsight, I should have kept the camera on the very same spot for longer instead of sliding it along the trail and loosing focus in places :oops:)

    PS See my post in another thread for more description.
     
    Last edited by a moderator: Nov 21, 2016
  9. Trailspotter

    Trailspotter Senior Member

    Here is a series of close-ups of the contrails from the same flight, UAE17 to Manchester.
    Screen Shot 2016-12-10 at 16.59.30.
    Emirates Airbus A380-861 A6-EEI, initially left a long hybrid contrail at 40,000 ft, with its two strands having different thickness. As the aircraft descended, the contrail get shorter and shorter and eventually stopped. The most persistent segment of the initial trail lasted about 5 minutes and looked from the distance like a solitary thin trail.

    Source: https://www.youtube.com/watch?v=-J6Qempn_7I


    Apart of the descent, the aircraft was banking toward my location, displaying its special "united for wildlife" livery. One or both these factors probably contributed to the asymmetric contrail evolution, as seen in the close-ups of different contrail segments. Despite having been entrained in the wake vortices, longer contrails had uneven density and dissipated quicker in weaker parts. This is, presumably, because in the weaker parts, the mixing of exhaust with ambient air has already passed through the condensation stage back to non-saturated conditions, where contrail dissipates, entrained or not.
    Screen Shot 2016-12-10 at 16.45.25.
    Before the exhaust contrails got entrained into the wake vortices, parts of them were already entrained in minor vortices closer to the airframe. Such a vortex (from a wing flap?) is more apparent in the close-up of a shorter contrail:
    Screen Shot 2016-12-10 at 16.47.56.
     
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  10. Trailspotter

    Trailspotter Senior Member

    Found on youtube a two year old video showing a close-up of the evolution of an aerodynamic contrail (for about ten seconds from its formation; 1:00 - 1:14):

    Source: https://youtu.be/RGK5wTJJV-A?t=55s

    Despite the different airframes, there are clear similarities to my recent video in #4.
     
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  11. Trailspotter

    Trailspotter Senior Member

    Yesterday, December 22, 2016, I filmed a few planes that fly from the British Midlands to Europe and pass by my location still climbing up to the cruising altitude. Usually, they are contrail-less, but in a winter morning yesterday they started forming contrails at about 27,000 ft or less. I twice caught the moment when contrails came into existence behind ascending planes with being initially very faint and a couple of the plane lengths behind the engines:

    Source: https://youtu.be/pTyJ9bo9Rb8
     
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  12. Mick West

    Mick West Administrator Staff Member


    Source: https://www.youtube.com/watch?v=NHyhi9Mi1Ng


    Dec 19th 2016 at 7:50AM PST, Shingle Springs, 4x speed, zoomed and tracked, contrast enhanced.

    Interesting in that it seemingly shows the contribution of the crow instability decomposition of wake vortices to the formation of pendules in a persistent contrail.
     
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  13. Trailspotter

    Trailspotter Senior Member

    It does. I have taken quite a few videos myself showing the same effect. I have not put them on youtube yet, however, as I still hope to take one of a better quality that would not require a lot of post-prosessing.
     
  14. Mick West

    Mick West Administrator Staff Member

    I think you are going to always be looking at a trade-off between the visibility of the vortices and the solidity of the larger contrail. A lot of the time the vortices are not visible at all. Being backlit by the sun and in barely-persistent conditions seem to help.

    It's interesting to compare what we see here with the desciption by David Schultz
    http://onlinelibrary.wiley.com/doi/10.1002/wea.2765/full


    Because I don't really see (in my above video) the formation of ring vortices being a key part. It seems more like the vortex pair is continually descending, and stops descending when one of both vortices collapse. Remaining paired segments continue to descend. While they might well form rings, visually here it seems like they do not, and instead are simply decomposing along their length while they descend.

    However it might simply be that the "join" at either end is not visible due to lower rotation speed. If you look at images of just the vortices alone in a hybrid contrail we see the sections do all seem to form "rings".
    [​IMG]

    Still, I don't think it's specifically the vorticity of the rings advecting the pendules, it's essentially the continued advection of the vortex pair
     
  15. Trailspotter

    Trailspotter Senior Member

    Precisely. In the contrail that passes closer to the Sun the denser vortices tend to shine through:
    Screen Shot 2016-12-29 at 19.24.56. Screen Shot 2016-12-29 at 19.21.13.
    Also, in the contrails of certain types of aircraft the vortices appear to be more visible, as the airframe probably determines the proportion of the exhaust contrails being entrained in them.
     
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  16. Trailspotter

    Trailspotter Senior Member

    A close-up of the contrails stopping on descent:

    Source: https://www.youtube.com/watch?v=YvbTcd3lAbA

    Interestingly, the Boeing 787 short contrail has three strands that distinguishes it from the contrails of other heavy two-engine planes:
    IMG_9313.JPG
    Both engine contrails appear "bifurcating" with inner strands merging together. The same effect can be seen in a longer and denser contrail:
    [​IMG]Dreamliner Overhead by Matthew Gjedde, on Flickr
     
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  17. Trailspotter

    Trailspotter Senior Member

    Pakistan International Airlines Boeing 777-2Q8(ER) AP-BMH, ascending from the Birmingham Airport, leaves a faint aerodynamic contrail between 25,000 and 28,000 ft that gets thicker with time:

    Source: https://youtu.be/4h-IE1OZPZo

    Screen Shot 2017-03-28 at 12.51.24.
     
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  18. Trailspotter

    Trailspotter Senior Member

    Last edited: May 18, 2017
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