Author Topic: How Airplanes Fly: A Physical Description of Lift (Read 14420 times)

W.D. Roland · « **Reply #50 on:** February 26, 2012, 06:25:48 PM »

Have decided to start with the Java Foil as I do have Java up and working in my machine. Will download tonight.
Looks like I may have more questions on set up and use of the program than on airfoils and airflow.

W.D. Roland · « **Reply #51 on:** February 26, 2012, 06:27:16 PM »

Ridiculous file size limit is only going to allow 1 page per post
2nd page

W.D. Roland · « **Reply #52 on:** February 26, 2012, 06:28:18 PM »

Where ever you go there you are!

W.D. Roland · « **Reply #53 on:** February 27, 2012, 06:34:44 AM »

Forgot to mention that the imiges at least on my computer look best by right clivk, open new tab or window,click image again for full enlargement and best clarity.

Has been many years since actualy reading some of this stuff but if my memry is correct there is a way to get the vacume at zero energy cost.

Looks like these flow sims are gona be handy!

Brett Buck · « **Reply #54 on:** February 27, 2012, 04:01:26 PM »

Quote from: W.D. Roland on February 27, 2012, 06:34:44 AM

Forgot to mention that the imiges at least on my computer look best by right clivk, open new tab or window,click image again for full enlargement and best clarity.

Has been many years since actualy reading some of this stuff but if my memry is correct there is a way to get the vacume at zero energy cost.

I looked at running a separate suction/BLC engine for a while. The hardest issue was getting a plenum for the suction around the leadouts and other control hardware in the wing.

At this point, of course, it doesn't make much difference since we had good engines, getting sufficient lift is no longer an issue. I think the big problem *now* is maintaining consistent flow conditions throughout the range of control deflections, and control response linearity. Which this may or may not help.

Brett

Howard Rush · « **Reply #55 on:** February 27, 2012, 04:44:31 PM »

I ran into a former boss at work and asked him what he was working on. "Natural boundary layer control," he said. "Oh," I asked. "You mean blowing and sucking?" "No," he replied. "That's unnatural."

Brett Buck · « **Reply #56 on:** February 27, 2012, 04:58:48 PM »

Quote from: Howard Rush on February 27, 2012, 04:44:31 PM

I ran into a former boss at work and asked him what he was working on. "Natural boundary layer control," he said. "Oh," I asked. "You mean blowing and sucking?" "No," he replied. "That's unnatural."

What consenting adults do in the privacy of their homes is no ones business but theirs.

Brett

Larry Cunningham · « **Reply #57 on:** February 27, 2012, 06:56:36 PM »

Quote from: wwwarbird on February 26, 2012, 12:10:21 AM

Holy crap, we've got a novel upstairs. Like I said earlier, if it's got enough power it will fly. The wing is only a secondary consideration.

You'll notice they've taken all the fins off rockets.. You have to go back to Rocky Jones - Space Ranger or Forbidden Planet to find a decent set of fins. {Oops - latter ship was a saucer}

L.

PS - yep, and there's Howard correcting me, right away!

"Many phenomena of common experience, in themselves trivial - for example, the
cracks in an old wall, the shape of a cloud, the path of a falling leaf, or the froth on a pint
of beer - are very difficult to formalize, but is it not possible that a mathematical theory
launched for such homely phenomena might, in the end, be more profitable for
science?" -Rene Thom

W.D. Roland · « **Reply #58 on:** February 27, 2012, 10:48:52 PM »

Brett
I was thinking that with a sheeted wing ,Millennium type comes to mind, vertical shear webbing in the aft section or behind rear lead out with holes in ribs would leave only the ducting inside fuselage to intake necessary.
Simple holes drilled through the trailing edge......
Our 2 stroke engines should pump plenty enough especially with the waste out of the exhaust during overlap/blow down. Tuned pipes trying to stuff the waste back up the exhaust might kill a large % of the pumping.

Another idea is venture or 2 under each wing tied directly into 'wing' chambers.
Make em look like jet engines?

I once played around with the numbers on a 2liter CanAm type car in a class where wings were not allowed.
Similar to Halls sucker car but with out auxiliary engines. The normal engine figured at 90% VE applied on the large
bottom surface made for some very usable down force. Never did try it as Ground effect was doing the job.
Did consider using it to reattach boundary layer just after beginning of diffuser so that steeper diffuser angle could be used.
Never got around to it.
Large super air filters would be required.

The entire original Buck Rogers (30s?) can be found on Youtube. Was fun to watch.

Ted Fancher · « **Reply #59 on:** February 28, 2012, 03:22:02 PM »

Quote from: Brett Buck on February 27, 2012, 04:58:48 PM

What consenting adults do in the privacy of their homes is no one's business but their's.

Brett

Corrected for punctuation. Consider this my contribution to the discussion.

Ted

W.D. Roland · « **Reply #60 on:** March 01, 2012, 01:10:58 PM »

Spelling police always welcome!

Brett
I agree that the common current look alike stunters have all the lift necessary and the even 60s and 70s vintage non piped engine will do the job for power if airplane is light enough. The ones of this type I have need little to no improvement.

My interest run more to the scalish radial engined WW2 fighters and radial engined Pre War Racers.
Reducing wing area by improved wing design and lighter construction is what my quest is.

The first test subject for checking out Rabes airfoils is ready but looks like a year + before I can do any flying.
By then drawings for 2nd will be ready, based on simpler and lighter subject.
Also the 3rd ones drawings will be close to finished and awaiting finalization after results from 1st 2 are known.
Hope to use scale or nearly so wing areas.

Chuck Feldman · « **Reply #61 on:** March 02, 2012, 09:03:12 AM »

As the wing moves forward the pressure on the bottom surface becomes higher that the pressure on the upper surface. We call this lift.
That makes flight possible. Going beyond that explanation of lift just makes things complicated. If you like complications go beyond that and enjoy yourself.

Mark Scarborough · « **Reply #62 on:** March 02, 2012, 10:29:37 AM »

Chuck, I understand your perspective, but some of us really want to understand this stuff on a real basis, it helps trim and fly our models to a higher level, not to mention, knowledge is a good thing regardless

Brett Buck · « **Reply #63 on:** March 02, 2012, 10:39:22 AM »

Quote from: W.D. Roland on March 01, 2012, 01:10:58 PM

mprovement.

My interest run more to the scalish radial engined WW2 fighters and radial engined Pre War Racers.
Reducing wing area by improved wing design and lighter construction is what my quest is.

The first test subject for checking out Rabes airfoils is ready but looks like a year + before I can do any flying.
By then drawings for 2nd will be ready, based on simpler and lighter subject.
Also the 3rd ones drawings will be close to finished and awaiting finalization after results from 1st 2 are known.
Hope to use scale or nearly so wing areas.

Don't overestimate the advantage of the aft high point airfoils. I don't think there is anything wrong with them and the idea is sound enough, but we have been flying some awfully dense models with excellent results using the exact opposite principle.

Getting the power right is A LOT more important than getting the exact right airfoil.

Brett

Brett Buck · « **Reply #64 on:** March 02, 2012, 12:14:50 PM »

Quote from: Ted Fancher on February 28, 2012, 03:22:02 PM

Corrected for punctuation. Consider this my contribution to the discussion.

Ted

I think that possessive pronouns (ones and theirs, like yours or ours) require no apostrophe, but I could be wrong.

Brett

Jim Thomerson · « **Reply #65 on:** March 02, 2012, 12:26:09 PM »

Brett, I think you are correct about possessive pronouns, with one exception. One's, as a possessive, is properly apostrophized.

Sean McEntee · « **Reply #66 on:** March 02, 2012, 02:17:51 PM »

I just close my eyes and pray that it gets off the ground. And it works for the most part....except for that one takeoff in Farah.....

W.D. Roland · « **Reply #67 on:** March 02, 2012, 05:19:31 PM »

Brett
Spelling, punctuation and language police rarely have real input on subject. Just time wasted. If they don't comprehend the meaning wouldn't it be more productive to ask for clarification?

Although I like the possibility of increase flow over the flaps with the thick aft section airfoils the possibility of
Cp moving rearward at AOA and this pitching added to the flaps pitching requiring larger and or more powerful
elevator with most likely increase drag could lead quickly into a viscous circle.

Anxious to get this year over with so I can get back to flying and testing.

This might be interesting for some.
Example of vicious circle:
This is the sort of problem Ford had in the GT-40MkII 427 program in trying to bring the cars down from over 220mph to 35-40mph for Mulsanne corner.
Around 4.5 Million ftlb of kinetic energy converted to heat in 7seconds every 3.5 minutes with out fail for 24hrs, while also dealing with 9 Million involve in the other 5 apps of the brakes per lap.
Bigger brakes = more rotating mass needed bigger brakes adding more mass.......

Enzo should never have pissed off Henry Jr.

Just something that always blew my mind.

Howard Rush · « **Reply #68 on:** March 02, 2012, 05:38:12 PM »

Quote from: W.D. Roland on March 02, 2012, 05:19:31 PM

Spelling, punctuation and language police rarely have real input on subject. Just time wasted. If they don't comprehend the meaning wouldn't it be more productive to ask for clarification?

If the writer is too lazy to write right, I think it shows disrespect for the reader.

Brett Buck · « **Reply #69 on:** March 02, 2012, 07:32:30 PM »

Quote from: W.D. Roland on March 02, 2012, 05:19:31 PM

Brett
Spelling, punctuation and language police rarely have real input on subject. Just time wasted. If they don't comprehend the meaning wouldn't it be more productive to ask for clarification?

Although I like the possibility of increase flow over the flaps with the thick aft section airfoils the possibility of
CL moving rearward at AOA and this pitching added to the flaps pitching requiring larger and or more powerful
elevator with most likely increase drag could lead quickly into a viscous circle.

Well, I would say both of us grammar police (Ted and I) might have *some* idea how you might want to design relatively heavily loaded airplanes, but I would hate to risk wasting more of your time.

Brett

W.D. Roland · « **Reply #70 on:** March 02, 2012, 08:39:34 PM »

Me
I mostly pay attention to the meaning and ideas.
This coming from a Spelling, Language, and Grammar Teachers worst nightmare!

Thank goodness we got's da Spelled checker thingie.

I'm all ears on ideas from others.

john e. holliday · « **Reply #71 on:** March 03, 2012, 07:45:28 AM »

And spell checker doesn't get it right every so often. Four years of high school english and still barely passed.

Wayne Collier · « **Reply #72 on:** March 03, 2012, 08:13:24 AM »

Quote from: Howard Rush on March 02, 2012, 05:38:12 PM

If the writer is too lazy to write right, I think it shows disrespect for the reader.

Well said. Applauded.

REX1945 · « **Reply #73 on:** March 03, 2012, 09:33:47 AM »

It's amazing that little was said about viscosity, since no net lift is generated without it.

Without any math, I prefer the following explination (look up Kutta-Joukowski) :

   " A body with a sharp trailing edge which is moving through a fluid will create about itself a circulation
   of sufficient strength to hold the rear stagnation point at the trailing edge...."

The 2-dimensional part:

   The amount circulation depends on the speed and viscosity of the fluid, the angle of attack
   and the camber of the airfoil.

The three-dimensional part:

   The circulation (vortex) is progressively shed along the span of the airfoil until it gets to
   the tip, where the circulation is zero.

The physics of flying :

   The resultant airflow is 2 vortex "sheets" at each wing resulting in a net downflow of air.
   This down flow (wake) is a monentum change of the mass of air, and any time rate of
   change of momentum is, by definition, a force. The reaction to this force lifts the plane.

W.D. Roland · « **Reply #74 on:** March 03, 2012, 07:30:19 PM »

Tried that Rex

Seems our Expert brigade would rather peons not discuss or know anything they feel they know.

Now, if you would like to discuss how insulted they are over trivial things this seems to be the right place for that.
My Great Grandmother was like that, she also felt insulted and disrespected by most things in life.

May help hide those individuals lack of knowledge. Who knows?

Rex I do appreciate yours and the few others effort at discussing this

but elsewhere would be better.
Possibly one of the Formula car sites where information flows better and trivial B.S. is rare.
I guess whats at stake being much more than Balsa gives a much more realistic attitude.

W.D. Roland · « **Reply #75 on:** March 03, 2012, 11:09:57 PM »

3rd thread found this handy little micro pressure sensor.....range -1.2 to +2.5 psi
Looks possible 1oz AUW sensor, logging, power.

Howard Rush · « **Reply #76 on:** March 03, 2012, 11:37:11 PM »

Quote from: W.D. Roland on March 03, 2012, 07:30:19 PM

Seems our Expert brigade would rather peons not discuss or know anything they feel they know.

Said brigadiers figured out where you had been misinformed-- including, by the way, the pussyfooting around the Kutta condition-- and led you to the material that would teach you what you said you wanted to learn. This took some effort. Don't expect much more effort to be expended.

Mark Scarborough · « **Reply #77 on:** March 03, 2012, 11:45:44 PM »

Quote from: W.D. Roland on March 03, 2012, 07:30:19 PM

Tried that Rex

Seems our Expert brigade would rather peons not discuss or know anything they feel they know.

Now, if you would like to discuss how insulted they are over trivial things this seems to be the right place for that.
My Great Grandmother was like that, she also felt insulted and disrespected by most things in life.

May help hide those individuals lack of knowledge. Who knows?

Rex I do appreciate yours and the few others effort at discussing this but elsewhere would be better.
Possibly one of the Formula car sites where information flows better and trivial B.S. is rare.
I guess whats at stake being much more than Balsa gives a much more realistic attitude.

I dont get where you are feeling this from, it appears to me that the "experts" went to some lenghts to help you access information to understand. Not sure what it was that you were expecting?

W.D. Roland · « **Reply #78 on:** March 04, 2012, 10:58:28 PM »

Mark
Think I let the main provider of help in my direction know how much it was appreciated, Howard may have missed that.

What was i expecting? Discussion on improving use of our flaps In what I have trouble not calling Coanda.
I did collect a lot of links to stuff that probably will not have much on this but useful to say the least.

So back to old friends in the world of if one of us screws up we all might die, no time for the trivial B.S.

Looks like Javafoil is having problems with sections over 15% and sections at more than 8deg AOA.

Looking at( just found)
http://www.openfoam.com/

May take more memory than I can come up with and the learning curve is apparently long and steep.

Did find an old competitors tunnel for sale. They moved on to Military RPVs
I hear they are almost ready to give it away. Located in San Clemente, CA
http://www.hgpauction.com/?auctionid=157

So anyway...to those who's feeling may have been hurt over being insulted by those who my not meet your standard of written communication SMILE! Surely it will pass much faster than a flying device turned to a pile of
broken pieces.

Serge_Krauss · « **Reply #79 on:** March 05, 2012, 11:35:54 AM »

I've been away from the forums for a few days and missed a good part of this discussion. One thing I suspect has aggravated this thing is not always knowing the difference between items adding up to an effect (lift) and items which are different manifestations of each other. We confuse cause and effect. Some are translatable one into the other. Certainly bernoulli effects are difficult to analyze, since the paths of air do not start where the chord line intersects the leading edge, but rather a lower stagnation point, and the molecules that race across the top and bottom of the airfoil don't meet at the trailing edge.

Regarding XFOIL and Profili: I used Profili's ordinates for my airfoil, changed their percent-chord positions to allow more room aft for placing points for flat stationary flap surfaces to get my comparative results. I could have put in coordinates for a deflected flap that way too, but was analyzing a section with a stationary flap, for which XFOIL predicted maximum lift and stall performance superior to a regular airfoil. That make me think that - as Al and NACA discovered - just bending the aft end of an airfoil is not the best way to make flaps on models.

You guys ought to consider not carping at one another. Sometimes we inadvertantly...ah, I won't go there either. But we really ought to discuss this stuff in the appropriate forum sections.

SK