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Kasper wing and trapped vortices

AeroFranz

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I came across a high lift concept called "Kasper wing" or "trapped vortex". It seems like an elegant way of achieving high lift coefficients, but I find limited information. Does anybody know more about this? i would be interested in knowing if the windtunnel tests achieved good performance, and if a flight vehicle was built.

the picture comes from patent "AIRCRAFT WING WITH VORTEX GENERATION" by Witold Kasper, filed in the seventies
 

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sferrin

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Towards the back of the British Secret Projects: Hypersonics there is a concept that uses a wing like this.
 

KJ_Lesnick

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AeroFranz,

Honestly I would have never thought such a design would have produced that kind of airflow pattern... or at least produced an airflow pattern that would be beneficial to increasing lift.

I guess you learn something new every day...


Sferrin,

There's a hypersonic design that uses a wing set-up like this?

KJ
 

Simon666

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AeroFranz said:
i would be interested in knowing if the windtunnel tests achieved good performance, and if a flight vehicle was built.
From what I remember, NASA tested it and found nowhere near the by Kasper claimed lift coefficient and sink rate. Though there are some papers around on trapped vortices that show theoretically high lift coefficients can be obtained.
 

AeroFranz

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KJ_Lesnick said:
Honestly I would have never thought such a design would have produced that kind of airflow pattern... or at least produced an airflow pattern that would be beneficial to increasing lift.

Yeah, I guess that trapped vortices aerodynamics is not the most intuitive of things...I do know that wind tunnel tests proved that pick-up trucks get lower drag with the tailgate UP, as opposed to down, which is counter-intuitive.
Normally, the empty volume behind the cab gets filled with turbulent air and eddies.
But apparently, with the gate up, the space behind the cab gets filled with a trapped vortex, and the rest of the air flows over the trapped vortex as if that same space was faired over.
I guess that the whole point of te Kasper airfoil is to use trapped vortices to make oncoming air "think" that it's meeting a smooth, thick airfoil.
Question is, does this really work? i did read the abstract of a paper that tried to reproduce the experiments Kasper made, and that came somewhat short. But one paper is not enough evidence, especially since it was a grad student who performed it. I'd like to find out more before dismissing the idea as ineffective.
 

sferrin

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KJ_Lesnick said:
Sferrin,

There's a hypersonic design that uses a wing set-up like this?

KJ

No. It's a subsonic design. The hypersonics book has much (probably more than half) that isn't strictly "hypersonic" projects. Not that that's a bad thing as the book covers a lot of stuff that doesn't really fit in the other releases.
 

Trident

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I vaguely remember being shown something similar that was researched in windtunnel tests at the University of Stuttgart. It looked a bit different, in that it was essentially a zig-zag corrugated sheet but the principle was the same IIRC. Apparently, the project drew inspiration from insect wings, in particular dragon flies.
 

AeroFranz

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Trident said:
I vaguely remember being shown something similar that was researched in windtunnel tests at the University of Stuttgart. It looked a bit different, in that it was essentially a zig-zag corrugated sheet but the principle was the same IIRC. Apparently, the project drew inspiration from insect wings, in particular dragon flies.

Interesting. Do you remember if meant to work at low Reynolds numbers only (just like a dragonfly) or at full scale?
 

Trident

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I should perhaps mention that I saw it at an open day more than 10 years ago which means I was something like 12 years old. Being an aircraft nut I was intrigued enough that it stuck in my mind, but the finer points of its engineering context like Reynolds numbers were way above my head at the time, sorry ;) As far as I can remember research was very basic, just testing the properties of that airfoil without an eye on any concrete application.

If you're REALLY interested I could ask some questions, since I'm a student there nowadays. It could take a while though.
 

KJ_Lesnick

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AeroFranz,
Interesting. Do you remember if meant to work at low Reynolds numbers only (just like a dragonfly) or at full scale?

I actually was going to post something to that effect. Scale poses a huge issue on such things.


KJ Lesnick
 

AeroFranz

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Trident said:
If you're REALLY interested I could ask some questions, since I'm a student there nowadays. It could take a while though.

No pressure :). Low Re aerodynamics are still somewhat over my head, and I don't do anything at work on that scale anyway.
 

Simon666

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If you want an interesting paper:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940029018_1994029018.pdf

and link:

http://www.twitt.org/KASPBIBLIO.html
 

AeroFranz

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Good finds. Thanks Simon.
I think I will order that package of info from TWITT.
 

Mike Pryce

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The Boeing X-32 CV version used vortex flaps on the upper wing:

www.youtube.com/watch?v=yuP7Qm1OmIg

shows them in use. Remove brackets to use link (non flash users can't see link).
 

AeroFranz

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Thanks for the link. I think Boeing called that an "Apex" flap. It probably traps a vortex on the leading edge and mimicks a rounder, thicker leading edge. I don't know if another vortex forms behind that leading edge fence, though. Maybe they don't need it and can get by with the improvement in lift coefficient achieved on the leading edge.
 

Mike Pryce

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IIRC it was intended to create a 'thicker' leading edge, as you say, by trapping a vortex in front of it. This moved the cp forward, giving a nose up moment without needing elevon 'up' deflections, which reduce lift and require high AoA on approach (getting round the weakness of deltas on carriers). Seems to have worked - note the elevons are used mainly as flaps on the approach (plus roll commands).

The name Apex flap may have been due to copyright/patents.
 

KJ_Lesnick

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I didn't know that's what a vortex flap looks like! I thought it was a flap with vortex-generators on it...

Just to be certain here, the apex flap also produces, in addition to the "thicker-wing" effect the characteristics common with vortex lift (ultra high AoA's without stalling and such)?


BTW: I take it such a flap must be really precisely designed using CFD to make it work right (I'm amazed such a flap could work at a reasonable scale/reynolds-number without producing a horrifying amount of drag and turbulence)
 

AeroFranz

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KJ_Lesnick said:
Just to be certain here, the apex flap also produces, in addition to the "thicker-wing" effect the characteristics common with vortex lift (ultra high AoA's without stalling and such)?

BTW: I take it such a flap must be really precisely designed using CFD to make it work right (I'm amazed such a flap could work at a reasonable scale/reynolds-number without producing a horrifying amount of drag and turbulence)

I haven't bought any of the relevant papers yet, but it seems like Kasper Witold claimed gliding his tailless light airplane at 35 degree angle of attack with full controllability and low sinkspeeds in the order of 100 fpm. All the while getting an L/D of around 17, so if this were true (and I don't know that yet), the system should be very well behaved without much turbulence.
And yes, i suspect that trapping the vortex requires getting everything just right, like matching Reynolds number to appropriate location of the fences, and three-dimensional parameters such as sweep on the wing.
 

henryk

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Simon666 said:
If you want an interesting paper:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940029018_1994029018.pdf

and link:

http://www.twitt.org/KASPBIBLIO.html
[/quote/)



-for moore see poz.4; "The Kasperwing" book.

(Cl max=16-25!!!).

PS. Witold Kasper(Kasprzyk) was working in Seattle Boeing.
 

henryk

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henryk said:
Simon666 said:
If you want an interesting paper:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940029018_1994029018.pdf

and link:

http://www.twitt.org/KASPBIBLIO.html
[/quote/)


http://www.youtube.com/watch?v=VwbtaX8k8CE&feature=related

-short video with taxiing Kasper KC200(wooden 70-s construction with vortex generating flaps=red/black).

X-32CV have identical LE devices(APEX flaps).

-for moore see poz.4; "The Kasperwing" book.

(Cl max=16-25!!!).

PS. Witold Kasper(Kasprzyk) was working in Seattle Boeing.
 

henryk

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AeroFranz said:
I came across a high lift concept called "Kasper wing" or "trapped vortex". It seems like an elegant way of achieving high lift coefficients, but I find limited information. Does anybody know more about this? i would be interested in knowing if the windtunnel tests achieved good performance, and if a flight vehicle was built.

the picture comes from patent "AIRCRAFT WING WITH VORTEX GENERATION" by Witold Kasper, filed in the seventies

-that wing airfoil was realised in Kaspers KC200 2-place aircraft(70-es).
 

henryk

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henryk said:
henryk said:
Simon666 said:
If you want an interesting paper:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940029018_1994029018.pdf

and link:

http://www.twitt.org/KASPBIBLIO.html
[/quote/)


http://www.youtube.com/watch?v=VwbtaX8k8CE&feature=related

-short video with taxiing Kasper KC200(wooden 70-s construction with vortex generating flaps=red/black).

X-32CV have identical LE devices(APEX flaps).


-the only difference; hinge line is moore aft from leading age.
 

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