Wing vapour

[Liam]

Hi guys, I wondered if there is any implementation of wing vapour on any aircraft in flightgear, or if it is even possible with the current system. It certainly is a cool effect to be seen.

I wondered if anyone has tried it before. I know that the F14 has the vapour cone for when it reaches a certain speed.

This is what I mean by wing vapour:

[wookierabbit]

[Liam]

Very helpful thanks

[asdfasdf]

We can take one of the particle files and modify it so that the wing vapour only appears after a certain g-force. I'll do some experimenting.

[someguy]

Most of Dave Culp's planes generate simple wingtip vortices a bit short of stall.

[MAKG]

We can take one of the particle files and modify it so that the wing vapour only appears after a certain g-force. I'll do some experimenting.

Not being too familiar with the effect here, it doesn't look like a G-force thing at all to me.

As a speculation, what's happening is that the aircraft is flying in extremely high relative humidity (perhaps fog), and the lower pressure on top of the wings is causing the temperature to go down and the vapor to condense.

If this is anywhere near correct, what should trip it is high water vapor, high static pressure (so, low altitudes would be favored) and slow airspeeds. It will never happen above 36000 feet (the stratosphere is VERY dry, generally far below 1% RH) and is most likely by far on final approach.

[F22-killed-you]

It would definately be awesome, in particular for fighters!


Swindel

[erik]

Not being too familiar with the effect here, it doesn't look like a G-force thing at all to me.

As a speculation, what's happening is that the aircraft is flying in extremely high relative humidity (perhaps fog), and the lower pressure on top of the wings is causing the temperature to go down and the vapor to condense.

While high humidity would probably trigger the effect a little earlier than normal this effect is soleley due to lower pressure at the top side of the wing. This lower pressure is only caused by a high angle of attack; the aircraft nose points high above the velocity vector, which is quite common in landing configuration and at high g-forces.

Erik

[Liam]

It is triggured by multiple events, depending on the nature of the aircraft. Fighters in particular do it at a certain speed.


The long persisting contrails (which won’t persist very long) are from the outer end of the lowered flaps – where air is compressed and then expanded very rapidly, causing a lot of moisture to condense and spread outwards. You can also see there’s a lot of moisture in the air, it’s quite misty looking. certainly a temperature element is involved, in damp dawn/dusk conditions especially, on takeoff and landing on larger airliners, this effect occurs at a high enough speed. It is mainly frictional disturbance with moisture in the air if the moisture is high enough for it to rapidly expand and condense.




this is a nice little resource:
http://contrailscience.com/aerodynamic- ... contrails/

[Zan]

I took this up on irc some time ago, dunno if this derives from that conversation or just great minds thinking alike

Anyways, long time ago I tried to model the contrails physically, taking temperature and humidity etc into account. I have the nasal and xml files here: http://users.tkk.fi/~lapelto2/fgfs/contrail/ .

If someone is willing to make better textures and/or modify the nasal, feel free to do it. It shouldn't be too hard to figure out the air pressure over the wing (from jsb/yasim properties?) and launch the contrail if that is in certain range.

[asdfasdf]

I took Zan's engine contrails applied new textures and added them to the 777. Looks really cool, screenshots here: http://picasaweb.google.com/ahmed.allib ... reenshots#

[Zan]

That looks very promising! You can play with the variables at the top of contrail.nas to make the clouds bigger or change particles per second etc.

I wanted to add those contrails to AI models, so we could see contrails from high altitude AI or MP aircrafts, but there is no way to query the atmosphere at the other model's location. So while sitting on a runway, it is not possible to know if the AI aircraft is flying in low enough temperature to cause contrails... I guess the code needs a bit hacking to make that possible!

[Liam]

Also, I find the contrails on every plane currently in Flightgear (which has them implemented) to be extremely small.

If you look in the sky, the trails following are generally much bigger than the aircraft itself, Growing within meters of the plane.







(In FSX)

I remember when we had very nice heat turbulance coming out of the 777 and 787 models, Is this no longer able to be implemented? Or were they removed because of incapacity with the v1.9.1?

[someguy]

[quote="Liam"]Also, I find the contrails on every plane currently in Flightgear (which has them implemented) to be extremely small.
You might want to look at Dave Culp's jets, which leave healthy contrails above (IIRC) 30k feet. If your computer can afford the frame rate hit, you can edit the xml parameters in the DavePack folder to increase the particle life and crisscross the sky with ice crystals. Anyone with DavePack will see them according to their own settings.

The smoke on Dave's Bicentennial F-4 is robust, too.