Wings with holes

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  • #1
wolram
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I am sure i read about experiments with wings drilled with many tiny holes, the idea i think was to break up the boundary layer, did any thing come of out of these experiments?
 

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  • #2
Danger
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I suspect that you're thinking of 'laminar-flow skin'. If so, air is pumped out through the holes in order to prevent a boundary layer from forming. That's all that I've got; Fred can probably help you out a lot more.
 
  • #3
turbo
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I don't know about that, Woolie, but I have a friend who has been the National champion in his drag-racing class (he runs a classic 340 Duster) and is always competitive. He claims that if you polish intake manifolds, it supports laminar boundary-flow and that causes drag. He has his intake manifolds roughened to some arcane standards that he and his head-work specialist know, and he claims that the micro-turbulence in the air/manifold boundary acts like "little ball-bearings" as he puts it, to allow the bulk of the intake air to get to the cylinders with as little drag as possible. It makes sense, because if you can get the air rolling in little tiny pockets and the air is rolling to counter to the bulk air flow just at the boundary, and is rolling IN the direction of the bulk air flow just a little bit away from the air-manifold boundary, the bulk of the air would get a little boost from the rotating air cells near the boundary. He races in a class that is very restrictive about the modifications that are allowed to the car, so every little secret helps.
 
  • #4
russ_watters
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It actually goes both ways depending on how you are looking to do it. I have to run, but here's a link to the opposite:
In a conventional blown flap a small amount of the compressed air produced by the jet engine is "bled" off of the compressor stage and piped to channels running along the rear of the wing. There it is forced through slots in the wing flaps of the aircraft when the flaps reach certain angles. This air follows the flap profile, aimed downward to provide more lift. The bleed air prevents the boundary layer (slow-moving air that accumulates on the airframe surface) on the upper surface of the flap from stagnating, further improving lift. At low speeds the amount of air being delivered by this system can be a significant fraction of the overall airflow, generating as much lift as if the plane were travelling at much higher speeds.
http://en.wikipedia.org/wiki/Blown_flap
 
  • #5
wolram
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I don't know about that, Woolie, but I have a friend who has been the National champion in his drag-racing class (he runs a classic 340 Duster) and is always competitive. He claims that if you polish intake manifolds, it supports laminar boundary-flow and that causes drag. He has his intake manifolds roughened to some arcane standards that he and his head-work specialist know, and he claims that the micro-turbulence in the air/manifold boundary acts like "little ball-bearings" as he puts it, to allow the bulk of the intake air to get to the cylinders with as little drag as possible. It makes sense, because if you can get the air rolling in little tiny pockets and the air is rolling to counter to the bulk air flow just at the boundary, and is rolling IN the direction of the bulk air flow just a little bit away from the air-manifold boundary, the bulk of the air would get a little boost from the rotating air cells near the boundary. He races in a class that is very restrictive about the modifications that are allowed to the car, so every little secret helps.
I found at my expense in time that a sand blasted cylinder head gave improved pick up over one i had spent hours polishing, then found out it was shape that really mattered
and the surface is best left (cast).
 
  • #6
wolram
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  • #7
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Is this like a venturi effect?
It's not quite the same thing (but sorta close) and I don't have a source at the moment (I needed to use my neuron today and now it's over at the National Aviary resting), but the US Navy was looking at doing something like this for torpedoes.
 
  • #8
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These methods seem like a lot of work, for breaking up the boundary layer. The use of vortex generators do this with little cost and no mods to the wing exept mounting them.


Wolram,
I found this article maybe you have already seen it.
http://www.hero.ac.uk/uk/business/archives/2002/perforated_wings_take_fli1354.cfm [Broken]
 
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  • #9
All these methods don't really break up the BL but rather energize it so it will stay attached longer. This can be done by using VG's like frogman says but for high curvature area's this may not seem to be enough so holes are common think of the triple slotted flaps on the trailing edge of a 747.
 
  • #10
FredGarvin
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VGs always seem like the first line of defense for separation prevention. However, I believe Wolly is referring to vacuum assisted BL control that NASA was working on. Honestly, I haven't heard anything lately. I'll have to see if I can dig up any results or reports.
 
  • #11
Mech_Engineer
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An aero professor and some grad students at my university were developing a wing that instead of using control surfaces used tons of tiny holes on the top and bottom of the wing of the aircraft. Using an internal pump and ducting to the holes, they directly changed the pressure above/below the wing to control the aircraft's flight, taking over control which would normally be accomplished through control surfaces on the wing.

From what I understand, they were able to create a working testbed out of an R/C airplane. It is a very interesting sounding technology.
 
  • #12
Mech_Engineer
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Here is a link to Powerpoint presentation regarding an experimental application to tilt-rotor aircraft (e.g. Osprey).

http://www.ame.arizona.edu/research/aerolab/media/MAFC_XV-15_Media_and_VIP_Day_Briefing_Final.ppt [Broken]

Other links for similar experimental development:

http://www.ame.arizona.edu/research/aerolab/research/experimental.html [Broken]

http://www.ame.arizona.edu/research/aerolab/research/applications.html [Broken]
 
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  • #13
minger
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An aero professor and some grad students at my university were developing a wing that instead of using control surfaces used tons of tiny holes on the top and bottom of the wing of the aircraft. Using an internal pump and ducting to the holes, they directly changed the pressure above/below the wing to control the aircraft's flight, taking over control which would normally be accomplished through control surfaces on the wing.
We are doing similar things at my university as well. However, our flow control is done on missiles. Aside from holes (I don't believe ours are pumped though), they have a lot of other methods for flow control which are pretty neat.
 
  • #14
Danger
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I'll have to see if I can dig up any results or reports.
Please do! I'm totally unfamiliar with this, and it sounds fascinating.
 
  • #15
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The holes in the wings clogged too easily to make the system worthwhile.
 
  • #16
wolram
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The holes in the wings clogged too easily to make the system worthwhile.

Hi pantaz, did you work with this idea, if so do you have any data.
 
  • #17
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  • #18
wolram
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Thank you pantaz.
 

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