I suppose winglets are really a type of surf board to ride the vortex wave.
Posted on 03/21/2005 11:55:43 PM PST by Paleo Conservative
"I'm not an engineer and I didn't spend a night in a Holiday Inn Express, but I think the winglets are to reduce wingtip vortex drag."
LOL...I think we all can agree on reducing vortex drag.....my question is ... wouldn't extending the wing (horizontally) do the same thing? I worry about these things......
And I could tell you would do anything to denigrate a worthy design that performed beyond design margins when it had to - along with the skill and audacity of some brilliant pilots and crew. The number of pundits of the DC-10 family of aircraft who actually earned their living and staked their lives on that worthy design by operating it under all kinds of conditions speak volumes over your sophmoric rants on a subject you obviously know and care so little about.
No Boeing/MDC/Lockheed et al design is perfect and all machines eventually fail, sometimes at inopportune times and life is lost as a result. Such as the 737 "convertible" accident in Hawaii - you never know when illogical accidents will occur, no matter how hard you design through and/or around them.
If I remember correctly, there were at least two simple reasons wings were not extended as you suggested on past projects I worked on:
1. Lengthening the overall wing likely requires a redesign of the wing root area to strengthen it sufficiently to achieve the same increase in efficiency winglets would achive with no wing root changes.
2. Aircraft are designed to operate within certain "envelopes" that allow for some standardization of airport equipment, safety devices, etc. It would be a trade-off between the increase in efficiency costs versus flying a uniquely sized aircraft into "standardized" airports that would need modifications to handle it.
1. They reduce spanwise flow by damming it at the wing tip. This puts more (and faster) airflow over the upper camber and increases lift, and
Well, kinda. They work by reducing the tip vortex (the cause of the spanwise flow) at certain lift coefficients, thereby reducing the induced drag. Less induced drag = more lift.
2. They act as "tip sails". (At least on lower speed wings) they are canted slightly outward at the aft edge. That same spanwise flow pushes against the winglet, and the angle nudges the wingtip forward.
Right again, there is a forward component of thrust associated with winglets, except that it is only true for certain lift coefficients. That is why you only see them on airplanes that spend the majority of their flight time cruising (as opposed to fighter aircraft). .
Yes, extending the wing span reduces the tip vortex; if you could extend it infinitely it would be zero. Large endplates on the end of a finite wing have the same effect: imagine a wing in a wind-tunnel that spans from one wall to the other. There would essentially be no "tips" for the air to sneak around and cause the vortex.
That is why sail planes have a very large wing span: less tip vortex = less induced drag.
Troll. Flame bait. Hook, Line, Sinker.
Winglets increase an aircraft's operating efficiency by reducing what is called induced drag at the tips of the wings. An aircraft's wing is shaped to generate negative pressure on the upper surface and positive pressure on the lower surface as the aircraft moves forward. This unequal pressure creates lift across the upper surface and the aircraft is able to leave the ground and fly.
Unequal pressure, however, also causes air at each wingtip to flow outward along the lower surface, around the tip, and inboard along the upper surface producing a whirlwind of air called a wingtip vortex. The effect of these vortices is increased drag and reduced lift that results in less flight efficiency and higher fuel costs.
Winglets, which are airfoils operating just like a sailboat tacking upwind, produce a forward thrust inside the circulation field of the vortices and reduce their strength. Weaker vortices mean less drag at the wingtips and lift is restored.
I suppose winglets are really a type of surf board to ride the vortex wave.
My colleague also mentioned that the visit to France by SecState Rice was a "seduction operation" that was totally successful and now anti-Americanism has been throttled back a bit. Seems Chirac and others were smitten with our intelligent, cultured, and frankly hot Condi!
Just what you'd expect from the French! They can't help themselves! Obviously, they do not hate America, they're just jealous of its sexy power.
I suppose what I said is a little misleading, in the sense that more lift is not created by (as in your example) changing the geometry of the wings. In your case of extending the flaps, additional lift is generated by increasing the wing area, lengthing the chord, and putting more camber in the wing section. Of course, as you mentioned, the penalty you pay is an increase in parasitic and induced drag, as well as pitching moment.
Now here is where it gets a little involved without pictures. The tip vortices produce a local upwash in front of the wing and a downwash behind the wing. The practical effect of this is to reduce the "local" angle of attack (near the wing as opposed far away where the upwash has no effect) that the wing sees and thereby reducing the lift.
Here's the tricky part: lift is defined as a force perpendicular to the direction of the airflow and drag as being parallel to it. The difference between the lift defined by the freestream direction and the lift defined by the "local" direction ends up producing a force in the freestream drag direction. Hence the name: induced drag.
The upshot of all this is that if you reduce the induced drag, you recover the lift that was lost, i.e. more lift.
P.S. Just as a side note, none of this impresses the little ladies. I'd stick with the daring exploits and embellished war stories.
LOL - Just read your profile. You probably already knew all that.
LMAO!
That's a cute pig, i've seen winglets at the pet store, they don't look as good after they have fallen off. ;)
Thanks for the info bandit!
Thank you very much for the lesson on winglets!
I have seen them but didn't know the name until this post. :)
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.