ferpe
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Boeing Testing Laminar Flow On 787

Fri Jun 17, 2011 10:01 am

Boeing have now started the tests with laminar flow improvement technology on the 787 tail:

http://www.flightglobal.com/articles...aminar-flow-control-for-787-9.html

There is reasons to believe this article is essentially correct, if so this is exciting stuff    . Increasing the laminar flow partion on the wings have been the desire since the P58 Mustang laminar flow profiled wing, yet it has not been introduced into mainline airliners to date IIRC.

The elegance of the B system is that the suction comes from parts of the wing which has low static pressure, ie no active parts    .

I know there are test with increasing laminar flow on test wings for A in the 2015 time frame, is this similar technology? (It can only be similar as B have patented their implementation).
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 17, 2011 12:08 pm

The hybrid laminar flow control (HLFC) modification is installed on test aircraft ZA003 in a limited area on the leading edge of the Boeing-built vertical stabiliser, one-quarter to one-half of the way up the fin, estimated to be positioned on the adjacent forward panels between ribs 3 and 7, and below the HF antenna.

ZA003, KSBD, June 8.

Original uploaded by KSBD Photo, see for other sizes : http://www.flickr.com/photos/ksbdphotos/5813364256/in/photostream
For more photos of ZA003 see : http://www.flickr.com/photos/ksbdphotos/page6/
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travelavnut
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 17, 2011 12:56 pm

Could somebody explain laminar flow, and its advantages, in laymens terms? I get the concept, I think, from Wikipedia;

http://en.wikipedia.org/wiki/Laminar_flow

But from the Wiki article I actually get the impression that all wings have laminar flow, or am I wrong on this? Also; what's so special about the implementation on the 787 that it couldn't be done on previous airliners? And why the apparant gap between the P-51 and the 787?

Thanks!
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autothrust
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 17, 2011 1:04 pm

Quoting ferpe (Thread starter):
Boeing have now started the tests with laminar flow improvement technology on the 787 tail:

What the news, that Boeing is second as always? Airbus has tested laminar flow on the A320 already in the year 1998!!

Quote:
Airbus Industrie has begun flight testing its A320 development aircraft, equipped with a newly developed vertical tailfin, which incorporates laminar flow technology to reduce air friction and significantly reduce fuel consumption.
http://www.flightglobal.com/articles...airbus-flies-laminar-flow-fin.html
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ferpe
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 17, 2011 1:26 pm

Quoting Autothrust (Reply 3):
What the news


Beacuse they do not have any air pump, that is!
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474218
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 17, 2011 1:35 pm

Quoting ferpe (Thread starter):
the 787 tail
Quoting Autothrust (Reply 3):
vertical tailfin

I wish people would use the proper terminology! It is the "VERTICAL STABILIZER".

Quoting Autothrust (Reply 3):
What the news, that Boeing is second as always? Airbus has tested laminar flow on the A320 already in the year 1998!!

Suggest reading the following, which provides the history of Laminar Flow testing, from the 1930's.

http://www.nasa.gov/centers/dryden/pdf/88792main_Laminar.pdf
 
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 17, 2011 2:08 pm

Quoting 474218 (Reply 5):
It is the "VERTICAL STABILIZER".

Tell that to Flightglobal i just pasted the text.   

The Laminar Flow testing of Airbus was a European program, called HYLTEC (HYBRID LAMINAR FLOW TECHNOLOGY)

http://ec.europa.eu/research/growth/...autics-days/pdf/posters/hyltec.pdf

[Edited 2011-06-17 07:11:26]
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ferpe
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 17, 2011 3:09 pm

What you boast above is what has been acheived today, experiments.

The new thing is that a large serious player is now saying it is going to be used on my very important civil airliner.
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BMI727
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 17, 2011 7:40 pm

Quoting ferpe (Thread starter):
yet it has not been introduced into mainline airliners to date IIRC.

The Honda Jet is set to use a natural laminar flow wing.

Quoting travelavnut (Reply 2):
Could somebody explain laminar flow, and its advantages, in laymens terms? I get the concept, I think, from Wikipedia;

Having laminar flow reduces the skin friction from the air flow. Of course, the mixing of a turbulent boundary layer introduces more energy to delay flow separation so while airliner engineers are seeking to retain more laminar flow, engineers designing smaller aircraft often seek to make the flow turbulent. Airliners sometimes utilize vortex generators to get a similar effect.

Quoting travelavnut (Reply 2):
But from the Wiki article I actually get the impression that all wings have laminar flow, or am I wrong on this?

They do, for a little while. Just using rough calculations, the flow over an airliner moving at 500 mph is laminar for about 3 cm.

Quoting travelavnut (Reply 2):
And why the apparant gap between the P-51 and the 787?

Reynolds number. Airliners will work at a higher Reynolds number range than a P-51, mostly because they are bigger but are also a bit faster as well.
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David L
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RE: Boeing Testing Laminar Flow On 787

Sat Jun 18, 2011 9:51 am

Quoting 474218 (Reply 5):
I wish people would use the proper terminology! It is the "VERTICAL STABILIZER".

I suspect the "proper terminology" can vary from place to place. I've seen "tailfin" and "tailplane" (horizontal stabiliser) used in technical articles in the UK over the years. There are similar differences in car terminology, e.g. trunk/boot, hood/bonnet, turn-signals/indicators.
 
ferpe
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RE: Boeing Testing Laminar Flow On 787

Wed Jun 22, 2011 4:40 am

As written in the Civil Avition forum I expect B to apply this technology in full on the 797 NSA project, this will be the technology that gives B a distinct advantage over the A320NEO. One can only speculate on how much drag reduction one can achieve when applied on wings and tail but 5% should be achievable IMHO, which is quite a feat.
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RE: Boeing Testing Laminar Flow On 787

Thu Jun 23, 2011 4:39 am

Quoting travelavnut (Reply 2):
Could somebody explain laminar flow, and its advantages, in laymens terms?

Smooth, rather than erratic flow. Turn your water faucet on low...you'll get a nice smooth "glassy" stream for some distance (laminar) that will be come all wiggly and jagged (turbulent). Laminar flow has lower skin friction, hence lower drag.

Quoting travelavnut (Reply 2):
But from the Wiki article I actually get the impression that all wings have laminar flow, or am I wrong on this?

All airliner wings are turbulent (right now). They're too large and fast to be laminar over more than a small fraction of the wing. People often confuse turbulent with separated...they're very different.

Quoting Autothrust (Reply 3):
What the news, that Boeing is second as always? Airbus has tested laminar flow on the A320 already in the year 1998!!

Nice try...Boeing did it on a 757 in 1985 (http://www.nasa.gov/centers/dryden/pdf/88792main_Laminar.pdf). Not to say that Boeing did it *first*...it's a far older idea than that, but let's keep the revisionist history to a minimum.

Tom.
 
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 24, 2011 5:38 am

From an intervju wiht J Leahy at Paris Airshow:

"If they (B) built an all-new airframe, it would be about up to 3% better on the airframe side. We did the studies before we did the NEO that an all-new, clean-sheet airplane aerodynamically could save us about 3% in fuel burn. Everything has to come from the engines."

http://leehamnews.wordpress.com/2011...ling-past-the-graveyard/#more-4722

He is clearly not counting on the application of laminar flow technology, once again I think this is what B has up the sleeve for the 797 and is the real reason why they want to go clean sheet. B want to exploit the technology now before the competition works out their own good and tested solutions to the problem and the advantage would be void.

[Edited 2011-06-23 22:39:22]
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 24, 2011 1:49 pm

Quoting ferpe (Reply 10):
5% should be achievable IMHO, which is quite a feat

Are you shocked at your own guess?   


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travelavnut
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 24, 2011 1:58 pm

Quoting tdscanuck (Reply 11):
Smooth, rather than erratic flow. Turn your water faucet on low...you'll get a nice smooth "glassy" stream for some distance (laminar) that will be come all wiggly and jagged (turbulent). Laminar flow has lower skin friction, hence lower drag.

Thanks a lot Tds!

Quoting tdscanuck (Reply 11):
All airliner wings are turbulent (right now). They're too large and fast to be laminar over more than a small fraction of the wing. People often confuse turbulent with separated...they're very different.

So what kind of changes are made to the 787 vertical stabilizer to generate this flow?

Also from your explanation I gather laminar flow over the entire wing of an airliner is impossible to achieve due to the size of the wing?
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tdscanuck
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 24, 2011 2:48 pm

Quoting travelavnut (Reply 14):
Quoting tdscanuck (Reply 11):
All airliner wings are turbulent (right now). They're too large and fast to be laminar over more than a small fraction of the wing. People often confuse turbulent with separated...they're very different.

So what kind of changes are made to the 787 vertical stabilizer to generate this flow?

Unfortunately, I can't talk about that. NASA has a good paper on the history of laminar flow control that's a good read to give you some ideas of the techniques: www.nasa.gov/centers/dryden/pdf/88792main_Laminar.pdf

Quoting travelavnut (Reply 14):
Also from your explanation I gather laminar flow over the entire wing of an airliner is impossible to achieve due to the size of the wing?

It's impossible if you don't do anything to control the boundary layer. The boundary layer is the slow moving layer of air right next to a surface. The longer the air stays there (the bigger the surface) or the faster the surface is going, the more energy the boundary layer picks up and, eventually, it goes turbulent. To prevent turbulent flow you either need to prevent energy from going into the boundary layer in the first place (natural laminar flow airfoils) or actively remove energy as you go. The latter is where most of the suction-based laminar flow control ideas come from...they use some kind of system to remove energy from the boundary layer. With active boundary layer control, you can keep the flow laminar over arbitrarily large surfaces at arbitrarily large speeds.

Tom.
 
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 24, 2011 2:53 pm

Quoting tdscanuck (Reply 15):
Unfortunately, I can't talk about that. NASA has a good paper on the history of laminar flow control that's a good read to give you some ideas of the techniques: www.nasa.gov/centers/dryden/pdf/88792main_Laminar.pdf

Thanks again Tds, got something to read this weekend 
Quoting tdscanuck (Reply 15):
The latter is where most of the suction-based laminar flow control ideas come from...they use some kind of system to remove energy from the boundary layer. With active boundary layer control, you can keep the flow laminar over arbitrarily large surfaces at arbitrarily large speeds

Ok, I think I'm starting to get this, complicated stuf though.
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 24, 2011 4:24 pm

Quoting travelavnut (Reply 16):
Thanks again Tds, got something to read this weekend


If you would have read Reply 5 you could have read the NASA report last week?
 
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RE: Boeing Testing Laminar Flow On 787

Fri Jun 24, 2011 6:54 pm

Quoting 474218 (Reply 17):

Completely missed that reply (and BMI's as well!), sorry!
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RE: Boeing Testing Laminar Flow On 787

Sat Jun 25, 2011 3:41 am

@Tom

I guess one could also allply this technology to the body surfaces and they should be quite effective there as well, why does one focus on a wings low pressure side? Because the air travels faster there or that boundry layer slows down because of the pressure gradient?
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RE: Boeing Testing Laminar Flow On 787

Sat Jun 25, 2011 3:55 am

Quoting ferpe (Reply 19):
I guess one could also allply this technology to the body surfaces and they should be quite effective there as well,

In principle, yes. However, given that the body surfaces are (usually) also the pressure vessel, the logistics of putting a bazillion little holes or vents or scoops or what-have-you in the body surfaces are more complicated.

Quoting ferpe (Reply 19):
why does one focus on a wings low pressure side? Because the air travels faster there or that boundry layer slows down because of the pressure gradient?

I'm not sure on the history on that one...in principle, it would work on either side. There may be stall benefits (delayed separation) to doing in on the upper surface though.

Tom.
 
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RE: Boeing Testing Laminar Flow On 787

Sat Jun 25, 2011 4:24 am

Quoting ferpe (Reply 19):
Because the air travels faster there or that boundry layer slows down because of the pressure gradient?

My guess would be that active boundary layer control might be able to reduce the adverse pressure gradient on the rear portion of the wing, which would delay separation.

Theoretically, I would think that if one could utilize the system on both sides of the wing, it could be linked and controlled in such a way to route air from the bottom to the top in certain (likely high alpha) situations almost like having a slotted flap.
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ferpe
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RE: Boeing Testing Laminar Flow On 787

Sat Jun 25, 2011 5:33 am

Quoting tdscanuck (Reply 20):
In principle, yes. However, given that the body surfaces are (usually) also the pressure vessel, the logistics of putting a bazillion little holes or vents or scoops or what-have-you in the body surfaces are more complicated.

Thanks Tom, actually this was my conclusion as well. Re practical implementation, I would assume laminar flow goes well with electrical de-ice as you need the slats natural plenum for your suction (instead of for bleed-air deice).

Quoting BMI727 (Reply 21):
Theoretically, I would think that if one could utilize the system on both sides of the wing, it could be linked and controlled in such a way to route air from the bottom to the top in certain (likely high alpha) situations almost like having a slotted flap.

I think you need air with much higher pressure differential then you get from those many small holes, any blown flaps or sorts need pretty high energy air. I would assume the air is not that high energy that you get in those laminar flow plenums.
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RE: Boeing Testing Laminar Flow On 787

Sat Jun 25, 2011 1:48 pm

Is such a system prone to icing? If a lot of water gets into the "holes" before departure and while climbing, couldn't this water freeze inside the system? Not only making it loose its advantage, but damaging the (passive) system, too and adding some pounds of weight? Or is the system heated?
 
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RE: Boeing Testing Laminar Flow On 787

Tue Jul 26, 2011 4:07 pm

Just to add to what B is working on, here is the A program, also aiming for the next generation SA:

http://www.flightglobal.com/articles...or-next-generation-narrowbody.html

Quite an informative article, my assumption on a drag gain of about 5% seems to not be that far of  
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RE: Boeing Testing Laminar Flow On 787

Tue Jul 26, 2011 5:52 pm

Quoting tdscanuck (Reply 15):
Quoting travelavnut (Reply 14):Quoting tdscanuck (Reply 11):
All airliner wings are turbulent (right now). They're too large and fast to be laminar over more than a small fraction of the wing. People often confuse turbulent with separated...they're very different.

So what kind of changes are made to the 787 vertical stabilizer to generate this flow?

Unfortunately, I can't talk about that.

My money is on super-smooth airframe coatings for the hardened wing/tailplane leading edges. May have something to do with the 787 nacelle leading edge which enables laminar flow on approx one sixth of the 787 nacelle length. See the last couple of posts in here:
787 Laminar Flow Nacelles (by Faro Dec 11 2009 in Tech Ops)

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RE: Boeing Testing Laminar Flow On 787

Fri Jul 29, 2011 4:49 pm



Quoting BMI727 (Reply 21):
My guess would be that active boundary layer control might be able to reduce the adverse pressure gradient on the rear portion of the wing, which would delay separation.

Perhaps. Boundary layer suction schemes generally aim to endow the boundary layer with additional momentum to penetrate further against a given adverse pressure gradient. I don't think such systems would have too much effect on the pressure gradient itself. Reducing the magnitude of adverse pressure gradients may require more drastic measures such as modifying the profile of the airfoil.
Quoting tdscanuck (Reply 11):
Not to say that Boeing did it *first*...it's a far older idea than that, but let's keep the revisionist history to a minimum.

Apparently, the British (Avro-Napier) were having a go at it sometime after the second world war.

http://www.flightglobal.com/airspace/media/aeroenginesjetcutaways/images/5583/avro-napier-flow-test-cutaway.jpg

http://www.flightglobal.com/airspace.../avro-napier-flow-test-cutaway.jpg

Regards, JetMech

[Edited 2011-07-29 09:56:22]
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tommytoyz
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RE: Boeing Testing Laminar Flow On 787

Fri Jul 29, 2011 11:09 pm

Another issue with laminar flow is that you need clean surfaces. If an airline doesn't keep their places clean enough, it might significantly interfere with any boundary layer control.

Another is stability and control of the aircraft. Let's say for instance, one boundary layer control malfunctions, let's say on one wing, but not the other. What happens is that one wing is producing far more drag and the wing far more lift. Unless this is compensated for, the aircraft will corkscrew out of control.

Another factor is that if the surfaces are dirty, damaged or wet, some laminar flow may be impaired, thus significantly reducing performance. But that is almost incalculable in advance, it would just happen in flight, so this would have to be managed and handled somehow.

All of these require changes to the designs and operation of aircraft, but why not? Putting all of the challenges aside, the difference in performance between an aircraft with a lot of laminar flow and one with almost no laminar flow, is like night and day. And it's not just the wing. The same laminar flow advantages apply to all surfaces, fuselage, stablizers, etc...
 
tdscanuck
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RE: Boeing Testing Laminar Flow On 787

Mon Aug 01, 2011 5:50 am

Quoting tommytoyz (Reply 27):
Another is stability and control of the aircraft. Let's say for instance, one boundary layer control malfunctions, let's say on one wing, but not the other. What happens is that one wing is producing far more drag and the wing far more lift. Unless this is compensated for, the aircraft will corkscrew out of control.

It depends if you're doing it for drag reduction or lift performance.

The former is more popular and less dangerous. The change between laminar and turbulent drag is meaningful (on the order of some %) but nowhere near as large as, for example, an engine-out situation on a twin. As a result, the adverse yaw of a failed boundary layer system on one wing should be well within the capability of the existing yaw control system.

Now, if you're using it for lift control you are, indeed, potentially in a lot of trouble. This was always a thorny issue with engine failure on aircraft with blown flaps for the same reasons.

Tom.

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