OT: Plane fuel

[Mike Tomlinson]

En el artículo , Blano escribió:

Another Woddles morph for the bit-bucket.

[news]

James Engineering Turbines modified a Lucas apu to run on sawdust and we ran it on gasified vegetable oil and pyrolysis offgas from a pressurised retort/kiln at 40psi.

AJH

[The Natural Philosopher]

I don't understand how you infer from their symmetry that they are doing nothing.

Inboard wing needs to be deep for structural reasons.

No designer is going to carry wing he doesn't need at cruise, at cruise!

Thats why all the flappy shit gets retracted.

[Vir Campestris]

Tip fences and winglets seem to have gone out of fashion.

Andy

[Vir Campestris]

Those sections are about the best you could have for getting them through the air with no drag. They may be generating some lift - but it won't be much. The inboard sections are deep for structural reasons, true, but that doesn't explain the asymmetry.

My guess - and I'm not an aerodynamicist, so it isn't much more than a guess - is that the inboard part is doing the bulk of the lifting at cruise, and that the outboard parts aren't doing much beyond acting as the fence that Blano mentioned. Feel free to point me at a proper reference - I'd be interested.

At landing speed the inboard bits sprout flaps, slots appear all along the leading edge, and I expect then the outboard parts earn their pay.

Andy

[Blano]

Hard to claim that given the A380.

[The Natural Philosopher]

Yeah. the dream-liner is SO yesterday isn't it?

[The Natural Philosopher]

It is considerable given the surface area,

The inboard sections are deep for structural reasons,

Oh dear. Asymmetry is how you make a deep section efficient to fly one way up. It doesn't help flying upside down tho. The section needs to be deep for fuel, spars and landing gear. The best section for that depth is selected. Outboard there is little need for strength, and so a thin section cam be used, and that is optimised for low drag and high lift are the cruising speed.

My guess - and I have studied aerodynamics extensively - is that you are about as wrong as it is possible to get.

On actual fact the way the design goes is this.

A high aspect ratio (long and thin) wing is best for efficiency as long thin wings have low tip vortex generation and therefore low drag.

Winglets or wing fences are all about controlling lateral airflow to reduce tip vortices.

Ideally a thin wing would be used across the whole span, as that is most efficient up near mach 1, but because the wing is long and thin and the outboard sections contribute quite a lot of lift, the bending moment at the wing root is very high: that requires a deep spar to provide stiffness and strength, hence the deep section inboard.

Tip and root sections are both asymmetrical, but its less obvious at the tip due to the thinner section.

Since the wing depth is there, inboard, its filled with fuel tanks. In fact the whole wing apart from the extreme tips is full of fuel.

[Vir Campestris]

Starting with your other post - Dreamliners seem to have very little in the way of winglets, fences or any of that stuff. What they _do_ have is a strong sweep near the tip combined with a slight upturn - not more than 15 degrees.

And Blano's comment - I'd missed them on the A380. They're not exactly enormous against that wing - certainly not compared with those on a 757. Which is why I suggested they may have gone out of fashion.

Most of your post I agree with completely. As I say, I'm an amateur at this. Especially when we start dealing with compressibility drag! But the section? Are you _sure_ it's asymmetric outboard? because it darn well doesn't look like it. I'll try to remember next time I'm near a modern jet.

I'd still like a reference. Flight Without Formulae isn't going to help here!

Andy

[Johnny B Good]

Actually, in the case of the SuperJumbo, those winglets were a vital part of the design to keep the wingspan within airport handling limits (a sort of "PanaMax" standard for civil aircraft).