What causes the condensation trails behind airplanes?

[Clausius2]

Everybody has seen the weak of condensed water which is left behind an aircraft when it flies in air.

To say the truth I am not an specialist in Aeronautical stuff, so I am searching a brave who tells me from where this weak comes from:

-does it come from the products of combustion (H2O released in combustion reaction)?

-does it come from the condensed water vapor present in surrounding air, due to the pressure exerted by aircraft structure on flight in the air flow?

Thanks in advance.

This ignorance is killing me...

 

[brewnog]

Ahoy there Clausius,

Do you mean vapour trails?

If so, it's just hot water vapour being emitted in the exhaust gases, and cooling. As you can see from the picture, they only emerge from the engines. You only get them at high altitude (troposphere, I think), so they're going to be either condensed, or actually frozen (which explains why they're visible). I suppose the actual source of the water is partly a combustion product, and partly water vapour held within the air just being heated up. You know more than me about gas turbines, but I suspect that in a typical commercial turbofan, the amount of water vapour being emitted due to combustion is much less than that which was in the air anyway, and has just been heated up.

The only other thing I can think you might mean is a sonic boom, like this: http://www.pinetreeline.org/misc/other/misc6f1.jpg

If so, you know much, much more about that than me, but I don't think that's what you meant anyway. The reason you might have had trouble Googling your question is because you meant to type "wake" not "weak".

Take care.

 

[Huckleberry]

They are also called contrails.
http://cimss.ssec.wisc.edu/wxwise/class/contrail.html

 

[brewnog]

They are also called contrails.

I'll remember that Huck, thanks!

We have a game going on at the moment whenever we're sitting outside our house. We lie on our backs, and watch, urm, contrails forming, and make bets on where they're going from and to.

"Ooohh, I reckon that one's Oslo to New York"
"Nahh, more like Copenhagen to Boston..."

Hours of fun!

 

[Clausius2]

The reason you might have had trouble Googling your question is because you meant to type "wake" not "weak".

Take care.

Ufff... Sorry, you're right. I was confused about that word, I recall it begun by letter W, but I was not sure.

Now I am going to teach you some of spanish. In this kind of situations one usually says:

Vaya metedura de pata!

BTW: thanks for your explanation.

 

[brewnog]

Didn't mean to embarrass you, but if I wasn't speaking my own tongue I'd pretty much expect people to point out my mistakes. Also I thought it might help with your search.


Ok, I'll give it a go...!

Vaya metedura de pata!

De nada!

 

[GENIERE]

… The only other thing I can think you might mean is a sonic boom, like this:http://www.pinetreeline.org/misc/other/misc6f1.jpg …[/URL]
Take care.

Not that I understand it, but I believe the photo is demonstrating THE PRANDTL-GLAUERT SINGULARITY and need not be due to supersonic airflow.

http://www.galleryoffluidmechanics.com/conden/pg_sing.htm


...

 

[Clausius2]

Not that I understand it, but I believe the photo is demonstrating THE PRANDTL-GLAUERT SINGULARITY and need not be due to supersonic airflow.

http://www.galleryoffluidmechanics.com/conden/pg_sing.htm


...

Yes, you're right. Anyway the purpose of this thread was not any sonic boom. Brewnog tried to expose it thinking I was referring to that. I am happy with his first explanation.