Effect of winglets on ground effect 1

[L10Captain]

My question is what effect do winglets have once the winglet-equipped wing has entered ground effect? Is induced drag reduced even further by the winglet installation or does ground effect minimize any further reduction in induced drag created by the winglet?

I am a professional airline pilot, but do not have an engineering background. Thanks to anyone who can provide me some additional information.

 

[DevelopedBug]

It's an interesting question, I know that the theory behind WIG/Akranoplans<sp?> is sketchy but it comes down to (at least in part) the tip vortex being trapped between the body/wing and ground providing you with a cushion of air which can double the L/D figures. However, I believe that the greater the vortex the more pronounced the effect, therefore if you are taking measures to reduce the vortices through the use of winglets then the effect should be less?

If you look at the various Russian Akranoplans they all have rather un-aerodynamic tips tending to suggest they are trying to generate as great a vortex as possible. there was a programme on TV here a few days ago about the Soviet Akranoplan projects and they showed footage of the &quot;Caspian Sea Monster&quot; as it was flying it looked like it was touching the surface and producing a huge wake with spray, it was in-fact the vortices wipping up the water, most impressive!

I had a friend at uni. who did his entire final year project on modeling WIG craft, I will try to get in touch with him and find out if he did any comparisons between conventional and winglet equipped aircraft.

Regards
-DevelopedBug

 

[235zzzo]

Hello Fellows!

Being a mechanic, however my predilect major was the applied instactionary aerodynamics, and in the mse course, turbulent flows with high gradients velocities fields, quite already many years ago.
If I understood, the question, indeed the winglets have the purpose to reduce the induced drag at the wing extremes, minimizing the vortices scale, wherever the plane is flying out or near the ground, thus the interaction between the vortices generation and the ground effect turns to be always smaller, resulting into a better aerodynamic plane behaviour.

Nevertheless, there are still some dynamic aspects to be referred, when you are reducing the vortices scale, you have higher circulation values, which means higher frequencies to be analysed in terms of the wing aeroelasticity in particular. Sometimes you can feel some odd vibration phenomena asking for some monitoring and expertise attention after the winglets assembly.

Merry Christmas to All!
zzzo

 

[Tord]

As winglets are an alternative to increasing span, but with less wing bending loads, and more strict speed constrictions, I would presume that in ground effect they do no good at all!

Tord

 

[Onemorechance]

I would think that if the winglets point down, the induced drag would be smaller because the vortex leaving the wing at the winglet is closer to and better neutralized by it's image in the ground.
On the other hand, if the winglets point upward, then the opposite is true, the vortex leaving the wing is moved further away from the ground and less neutralized by it's image, therefore results into higher induced drag than without winglet. Thats what I think, but I dont know for sure.

 

[swearingen]

As I understand it, the point of a winglet is to reduce the vortex drag to overcome its own parasitic and pressure drag plus some, for a net savings. It makes sense that they are designed to work at their highest efficiency at cruise (note that they only show up on 737's slated for longer hauls, for instance). When taking off and landing, your speed can be as little as 1/4 of cruise, which I suppose would greatly diminishing their effect. At those velocities, they probably create more drag than they save.