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Picture: Vortices

Pro Member Captain
Sean (SeanGa) Captain

http://www.airliners.net/photo/907531/

Check out the fascinating picture!

OK. In return of showing you this magnificent picture, you will unfortunately have to answer some of my questions below:

As far as I understand, the vortices coming from the winglets produce extra thrust, and the vortices from between the flaps increase drag. Is this correct? If this is correct, what makes the vortices from the winglets have a positive effect, while the other vortices don't? That's what I don't understand... I tried to get an answer from wikipedia, but I didn't really understand what was said there.

Are the vortice-like thingies coming from the tail wings (or whatever they're called) also vortices? - if not, what are they?

And what is that fog-like thing coming from the top of the wings?

Thanks in advance :p

Pro Member Chief Captain
CRJCapt Chief Captain

The Vortices's from the winglets minutely adds thrust because of the angle of the winglet redirects some of the vortices's in a positive direction. The true purpose in to reduce drag. Winglets reduce drag caused by the high pressure air below the wing curling up to meet the lower pressure air above the wing. All vortices's cause drag. The vortices's from the flaps and horizontal stabilizer are just drag.

The contrails or condensation trails (fog streaks) are caused by the aircraft flying through moist air normally in the morning when the temperature and dew point are close or the same. The air at the edge of the flaps is accelerated and caused to reach it's dew point. The fog above the wing is caused by the same conditions. As the plane flares or rounds out to land, the wing produces more lift. The air above the wing is traveling faster than the surrounding air and at a lower pressure. This causes the air to also be lower in temperature. If the air is moist and the dew point is close to the ambient temperature, this temperature drop reduces the air to it's dew point and you get fog. Smile

Pro Member First Officer
kianok First Officer

Gees..... i'm impressed Bow Down

Pro Member Captain
Sean (SeanGa) Captain

ah ok.. so the vortices which come from thew winglets don't provide additional thrust; they just reduce the drag caused by the vortices in the first place?

thanks for a great reply

Pro Member Chief Captain
CRJCapt Chief Captain

By redirecting some of the vortices's energy, They do provide a little thrust. Noticed only on long flights as increased range. The primary function is to reduce induced drag. The small amount of thrust is a bonus.Smile



Last edited by CRJCapt on Thu Jan 26, 2006 4:08 pm, edited 1 time in total
Pro Member Captain
Sean (SeanGa) Captain

alright!

hey, since I already made this topic...

you can't always see a vortice coming from the wingtip or winglet; does this mean that there is no vortice? or can vortices be invisible?

Pro Member Chief Captain
CRJCapt Chief Captain

They are always there. Almost all of the time they are invisible. That's what's makes them dangerous for following aircraft. It' called wake turbulence. It can roll the aircraft close behind inverted at low altitude, especially a smaller aircraft following a heavy aircraft. They are a threat during takeoff and landings. ATC uses separation distance/time to avoid this. Smile

Pro Member Captain
Sean (SeanGa) Captain

hm.. so what makes them visible then? the same that makes that fog thingie visible?

hope I'm not being to complicated now :p

Pro Member Chief Captain
CRJCapt Chief Captain

Yes. And then you are not seeing all of it, just where it leaves the tip. Wake turbulence can extend far behind an aircraft. Often hundreds of feet. Smile

Pro Member Chief Captain
Jonathan (99jolegg) Chief Captain

CRJCapt wrote:

Yes. And then you are not seeing all of it, just where it leaves the tip. Wake turbulence can extend far behind an aircraft. Often hundreds of feet. Smile

In the case of heavy aircraft such as the 747 at slow speeds with full flaps, they normally stretch back to between 2500 - 3000 feet Shocked Which is why, as CRJCapt has said, ATC impose strict separation rules

Wink

Pro Member Captain
Sean (SeanGa) Captain

2500-3000 feet... wow. that's nasty! Very Happy

Ok, I don't think I have further questions regarding this.. job well done guys Razz but if you are unlucky, I will post another. So beware Twisted Evil

oh... and btw, I think that 747 in your signature should back off before the cessna's vortices flip it over. lol

Pro Member Chief Captain
CRJCapt Chief Captain

Laughing In closing, 99 jolegg in correct. I should have said thousands instead of hundreds of feet. Here is a link for more information.

Pro Member Captain
Sean (SeanGa) Captain

QUESTION!!!!!!!!!!!!!!!!!!!!!

Most often (or always ???) when I see an aircraft cruising in the sky white stripes can be seen behind it. these aren't vortices right? probably just hot air which comes from the engines that mixes with the cold air and forms a cloud or something?

Pro Member Chief Captain
CRJCapt Chief Captain

No, they are condensation trails(contrails).
Smile
http://en.wikipedia.org/wiki/Contrails

Pro Member Captain
ARD-DC Captain

Since we're asking questions now anyway, hope you don't mind me throwing in one of my own, SeanGa...

CRJCapt wrote:

They do provide a little thrust.

they provide thrust? Shocked
Would producing thrust not require something to move; in order to actively force air into a specific direction? Doh!

There must be another meaning to 'thrust' that I am not aware of. Read

Pro Member Chief Captain
CRJCapt Chief Captain

The vortex which rotates around from below the wing strikes the angled surface of the winglet, generating a small lift force that angles forwards relative to the direction of flight - thus the energy in the vortex contributes to thrust rather than drag as it normally would. Smile

Pro Member First Officer
PH First Officer

Vortices = drag. There is no way to eliminate this drag it is the price paid for the generation of lift. It can be reduced by utilising wiglets.

Pro Member Chief Captain
CRJCapt Chief Captain

This is a long list of posts that maybe you did not see the first page of. We are talking about winglets. Yes the Vortices's are drag. The design of the winglet creates a small amount of lift that acts in a positive or forward direction. This is where the additional thrust is from.

http://en.wikipedia.org/wiki/Winglet

Pro Member Captain
Sean (SeanGa) Captain

this sentence basically says it all..

The vortex which rotates around from below the wing strikes the angled surface of the winglet, generating a small lift force that angles forwards relative to the direction of flight - thus the energy in the vortex contributes to thrust rather than drag as it normally would.

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