yodobashi
Posts: 137
Joined: Fri Sep 21, 2007 6:00 pm

Raked Wingtips ....

Sun Jan 03, 2010 1:24 pm

Hi folks,

As far as I understand, winglets and raked wingtips help to reduce drag, stopping the airflow from the top and bottom of the wings colliding at the wingtip and causing drag.

I shot the following picture from a Singapore B777-300ER wing whilst in the climb out of Singapore. The condensation on the upper wing seems to stop short of the wingtip about where the raked wing starts.

Does anyone know is this just coincidence, or does this show how the raked wing stops the airflow on the top of the wing from reaching the wingtip itself?

http://www.pbase.com/image/120774328.jpg

Any info would be greatly appreciated.
"The World is a book, and those who do not travel read only a page"
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Raked Wingtips ....

Sun Jan 03, 2010 5:28 pm



Quoting Yodobashi (Thread starter):
As far as I understand, winglets and raked wingtips help to reduce drag

Yes.

Quoting Yodobashi (Thread starter):
stopping the airflow from the top and bottom of the wings colliding at the wingtip and causing drag.

Not really. The reduce, but do not eliminate, the airflow around the end of the wing. Most of their effect (in terms of drag) actually happens fairly far from the tip itself.

Quoting Yodobashi (Thread starter):
The condensation on the upper wing seems to stop short of the wingtip about where the raked wing starts.

Does anyone know is this just coincidence, or does this show how the raked wing stops the airflow on the top of the wing from reaching the wingtip itself?

It's not a coincidence, but it's not a because the tip is stopping the airflow either. The condensation is caused by the pressure drop over the wing's upper surface...the amount of condensation is, roughly, a measure of the lift being generated at that wing station. The lift on all wings (regardless of winglet/raked tip/normal tip) goes to zero at the tip, so the upper surface condensation will also disappear at the tip. How close it gets to the tip depends, a lot, on how much lift the wing is generating, the atmospheric conditions at the time, and the wing shape.

Tom.
 
vikkyvik
Posts: 11907
Joined: Thu Jul 31, 2003 1:58 pm

RE: Raked Wingtips ....

Mon Jan 04, 2010 12:19 am

Couple photos to illustrate Tom's point:


View Large View Medium
Click here for bigger photo!

Photo © Ronald J Stella



Notice in the next two photos, the condensation basically spans the flap span. The portion of the wing that has flaps is generating far more lift than the tip, when the flaps are extended. You also get a powerful vortex off of the end of the flaps. These effects are generally best noticed on landing, as you're at a high flap setting.


View Large View Medium
Click here for bigger photo!

Photo © Tim De Groot - AirTeamImages
View Large View Medium
Click here for bigger photo!

Photo © Andrew Hunt - AirTeamImages

I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
BMI727
Posts: 11173
Joined: Mon Feb 02, 2009 9:29 pm

RE: Raked Wingtips ....

Mon Jan 04, 2010 1:40 am

I don't have a lot to add here, the other two mostly covered it.

Quoting Tdscanuck (Reply 1):
The condensation is caused by the pressure drop over the wing's upper surface...the amount of condensation is, roughly, a measure of the lift being generated at that wing station.

The condensation forms in lower pressure areas and on a wing, the areas with the lowest pressure (above the wing) create the most lift. This effect also appears as the shock collars in transonic flight and in some engines, if the conditions are right.
Why do Aerospace Engineering students have to turn things in on time?
 
yodobashi
Posts: 137
Joined: Fri Sep 21, 2007 6:00 pm

RE: Raked Wingtips ....

Mon Jan 04, 2010 11:30 am

Gentlemen,

Many thanks for your replies, I think I am now a little wiser as the reasons for the effects pictured.

Thanks again!

 Smile
"The World is a book, and those who do not travel read only a page"

Who is online

Users browsing this forum: B6JFKH81, SAAFNAV, SoJo and 17 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos