Does closed oval wing produce two vortex and downwash between them, like normal wing?

Question

Does closed oval wing like this in video produce two vortex and air between them goes in downward direction like on normal wing?

I think yes ,because cause for downwash is wing that push air down, not wingtip vortex. Some members here write that two wingtip vortex is cause for downwash.

Possible duplicate Do box-wings suffer from induced drag the same way as normal wings? See also: How is drag created from wingtip vortices? — , Dec 22 '21 at 13:27
The "as dupe" thread doesn't really address this sort of wing, and the differences between the box-wing and this one seem at least potentially enough to cause different dynamics here. IMHO, this question is sufficiently distinct to warrant its own answer. Voting to leave open. — Ralph J, Dec 22 '21 at 14:41
PS What the other post calls a box wing, covers both (the example there is different, but it's the same question). — , Dec 22 '21 at 17:07

score 5 · Accepted Answer · answered Dec 22 '21 at 19:42

5

A trailing vortex leaves the wing at each point where the wing's circulation (which is proportional to lift coefficient times chord) has a gradient over span. Only an infinite wing has no induced drag because its circulation is constant over span. "Hiding" the wingtips by using an oval wing is similar to closing your eyes so you don't see the approaching train - just as the train comes closer anyway, the wing sheds a vortex sheet. Basically, the oval wing is a biplane, so its two sides interfere just like the two wings of a biplane, reducing its overall efficiency. And not adding bracing means forfeiting the structural benefits of a biplane.

It's sad to see that some people still refuse to learn.

answered Dec 22 '21 at 19:42

Peter Kämpf

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"It's sad to see that some people still refuse to learn." Members are not problem, problem is 90% books describe wrong everything about wingtip vortex topic, I often read how wingtip vortex cause induced drag... – user707264 Dec 22 '21 at 19:52
@JurgenM Its obviously the people who put much work into a dud of a concept. Don't take things personally that are not meaning you. And you are right about 90% of those books out there. – – Peter Kämpf Dec 22 '21 at 21:25

Frog · Answer 2 · 2021-12-22T19:15:21.033

Given that the aircraft supports itself by accelerating air downwards, how could those vortices not exist?

At a large scale, the air movement around a heavier-than-air aircraft takes the form of a torus, with air moving downwards in the middle and upwards at the periphery. In practice this torus is typically highly distorted because the aircraft is moving quickly and the air moves relatively slowly. A conventional wing tends to concentrate the rotation at the wingtips, resulting in a tight vortex with relatively high airspeeds and therefore sapping a significant amount of energy that isn’t directly contributing to generating lift. There are several ways to mitigate this, such as washout, tip plates, and closed oval wings; to differing extents these make the vortices less concentrated and so the air circulates less quickly and saps less energy.

Thanks I shall add some more explanation. – Frog Dec 22 '21 at 19:05 — Frog, Dec 22 '21 at 19:05

Does closed oval wing produce two vortex and downwash between them, like normal wing?

2 Answers2