Explained: Video of plane leaving "6 chemtrails, then 2" [Mixed Exhaust and Aerodynamic Contrails]

funghi2

New Member
Im sure this has been debunked here but cant find the thread


been [discussing] "chemtrails" which has now morphed into SRM. somehow this video proves something to them...not the million possibilities but it proves specifically srm.

can you guys help me out here?
 
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Trailblazer

Moderator
Staff member
And the "four engines, two trails" is explainable by the fact that the exhaust contrails are not forming until some distance behind the plane, by which time the exhaust streams from the two engines on each side have presumably mingled?
 

Trailspotter

Senior Member
And the "four engines, two trails" is explainable by the fact that the exhaust contrails are not forming until some distance behind the plane, by which time the exhaust streams from the two engines on each side have presumably mingled?
No, it is not the case here, as the two streams from the same side mingle together at much larger distance. I think that contrails from the outer engines just stopped a bit earlier than from the inner ones. And there was a huge gap between the trails and the engines, indicative of very low humidity in that particular parcel of air, which is the most likely reason of the contrails stopping. In contrast, before the plane had flown in that parcel, it was flying through a parcel of very humid air, probably supersaturated relative ace and nearly saturated relative water. The pressure drop on the wing pushed the air temperature below the dew point, causing the immediate condensation of excess vapour and therefore the formation of aerodynamic contrail, which naturally persisted in the ice-supersaturated parcel.
 

Mick West

Administrator
Staff member
And the "four engines, two trails" is explainable by the fact that the exhaust contrails are not forming until some distance behind the plane, by which time the exhaust streams from the two engines on each side have presumably mingled?
Actually, I think it's just forming exhaust contrails from the inner engines at this point.
20160506-093039-05f39.jpg

If so, then that's very interesting. The conditions are obviously very marginal, as the plane stopped making contrails entirely a few seconds later.

I suspect this is due to interactions with the wake vortices altering the mixing curve.
 

Trailspotter

Senior Member
According to the Planefinder.net playback, it was a level flight at 30,000 ft:
Screen Shot 2016-05-06 at 17.53.17.png

Here is the Terra satellite image taken one hour before QF63 flew over Geelong:

A patchy cirrus cloud southwest of Geelong possibly was the one, into which the plane had flown one hour later.
 
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Mick West

Administrator
Staff member
20160506-094141-98vts.jpg
Models of contrail formation assume that the hot and humid exhaust air (point B) mixes linearly with ambient air (point A) until it reaches the same temperature and humidity.

During the mixing, it passes into the cloud formation stage (combined RHw > 100%), and thus forms a contrail.

So if two engines are producing different contrails in the same air conditions (a common point A) then either:
  1. The engines have a different point B - i.e. the exhaust temp & humidity differ between engines
  2. The mixing curve B-A differs between engines - and for at least one of them is non-linear.
Explanation #1 could happen if different engines have different throttle settings.

Explanation #2a could happen due to the way the wake vortices affect the engines differently - with the outer engines being pulled up and over, this might result in different local pressure changes, and hence (?) a different mixing curve? This seems unlikely to me - can you even get non-linear mixing due to pressure changes?

An alternative explanation #2b is that the formation of the aerodynamic contrail partially desaturates the local air, this essentially creates an intermediate "ambient" air that has lower relative humidity (as the water vapor has partially condensed). So the mixing curve will initially head towards this intermediate point. This air itself is also mixing with the ambient air outside the aerodynamic contrail, and the combined effects of a mixing of three masses of air results in a non-linear mixing curve.

There could also be a combination of factors from #2a and #2b, as the wake vortex motion could affect the mixing speed between the exhaust gases, the aerodynamic contrail air, and the ambient air.
 
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