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Airplane wing ?
5

Airplane wing ?

Airplane wing ?

(OP)
With all the constant talk about lift and airflow over the top of a wing.
I have one simple question, on average what is the percentage of airplane weight supported by the top of the wing?

RE: Airplane wing ?

The change in pressure distribution is about 70% decrease on the top of a conventional airfoil and 30% increase on the bottom (as well as some areas of pressure decrease on the bottom.)

Depending on what one considers, the full weight has to be carried on the bottom as air hasn't got tensile properties, but if one is designing for loads, you need a stronger surface on the top as the differential is higher.

RE: Airplane wing ?

Then strictly speaking the answer is none.

What I think you mean is what percent of the total lift force is generated by the top surface. Answer apparently 70%.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Airplane wing ?

It's not a simple question, it's simplistic.

There can't be a top without a bottom.

Lift is generated by a differential, acting at the mid-surface between top and bottom.

RE: Airplane wing ?

Now if one seals the wing, and installs a single vent, if that vent is pointing forward or aft or vented to the upper or lower surface, where does the lift get transmitted to the wing!

RE: Airplane wing ?

I agree with MJ, that you can't have the upper surface pressure without the lower. I agree that lift is the resultant of differential pressures on the two surfaces. But we can still say that lower surface pressure resultant is about 70% of the total resultant.

If you vent the lower surface to the upper, then you'll lose a lot of the lower surface pressure.

The situation is different for flaps, where the slot reenergizes the flow over the flap.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

(OP)
Similar to airfoil shaped race cars, that are a form of lifting body. The answer is there is very little lifting effect.
The lift that seems to be ignored is all on the bottom of the wing. It is the angle of the air impact cushion or relative wind that the wing skips upon just like a rock skipping on water.
There are symmetrical wings with the same shape above and below, and there are aerobatic planes that fly upside down.
A wing can create lift with zero airflow over the top, in a laboratory.
Flaps? They "CUP" the wing, to hold more air under the wing, it has nothing to do with the top.
Just drive down the road and stick your hand out the window at say 50 mph, you will feel what causes the lift. Yes mimic a wing with it.

RE: Airplane wing ?

So... you started this thread to teach everyone how wings REALLY work? Is that it?

RE: Airplane wing ?

OK, so... enginesrus...

Loads/forces due to lift are generated by + and - pressure distributions over the length of the wing-chord... which is a function of airfoil shape, angle of attack and air-velocity. Of course, this does not account for real-world factors... such as excrescence [friction] drag, laminar/separated flow... and in the case of a real-wing, the wing-tip vortices, torque and pressure distribution changes due to control surface deflections... and loads due to mass/inertia, etc...

Of course the span-wise sum of all loads [in discrete load-case 'sets'] defines the forces over the wing as an entity for various flight conditions.

Google "airfoil pressure distribution images" https://www.google.com/search?q=airfoil+pressure+d...

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Airplane wing ?

so you disagree with the "lift from circulation" theory ? What theory is this you're proposing ?

what is this "the angle of the air impact cushion" ?? never heard of it before ?

"A wing can create lift with zero airflow over the top, in a laboratory." ... okm I'll bite ... 'cause it isn't acting as a wing, but is a deflector ... simple fluid momentum.

"Flaps? They "CUP" the wing, to hold more air under the wing, it has nothing to do with the top." ... seriously WTF ? flaps increase the camber of the airfoil

"Just drive down the road and stick your hand out the window at say 50 mph, you will feel what causes the lift. Yes mimic a wing with it." ... yes, I think we all play with this one ... I know I do (as a passenger, mostly. Your hand could be acting like a wing (with circulation) or like a deflector. We have to be careful with how we interpret experiments (uncontrolled) that we can perform, our 1st hand experience of the world. Careful, that way "flat earth" comes ...

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

Newton vs. Bernoulli cage match!

RE: Airplane wing ?

Airflow over the wing top causes a reduction of pressure. Multiply the average pressure reduction (partial vacuum) by the area and you will get the lift contribution of the top of the wing.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: Airplane wing ?

(OP)
Has anyone seen a flat wing airplane?
Or maybe just a simple paper thin wing, paper airplane.
No airflow over a wing there causing a pressure difference.
And again what about a symmetrical wing with the same curvature on the bottom as the top?

RE: Airplane wing ?

A symmetrical wing at 0 degrees AoA produces no lift. To produce lift it tilts up to increase the amount of curvature above the stagnation point and decrease the amount of curvature below the stagnation point.

RE: Airplane wing ?

Quote (enginesrus)

And again what about a symmetrical wing with the same curvature on the bottom as the top?

Symmetrical wings can fly because they operate at a non-zero angle of attack.

'Regular' non-symmetrical wings sections also operate at some not-zero angle of attack; they don't perform well inverted because the way they are shaped for high efficiency in the mode of operation they are designed for means that if you flip them upside down, you would need huge angles of attack for them to work properly.

Symmetrical wings work on aerobatic planes because they are designed to function at relatively small angles of attack which are still possible to achieve when the fuselage is upside-down, without putting the airframe into some crazy attitude which would cause damage or generate a boatload of drag.

The two surfaces which form the rear section of an airfoil are not parallel, whether the section is symmetrical or not. As a result, for any possible symmetrical airfoil section, there is a range of AoA values from zero up to the divergence angle of the trailing edge where no part of the airfoil is oblique to the flow, BUT the length of the streamline over the top is longer than the streamline over the bottom - meaning there will be a pressure differential generated if the airfoil is moving. Pressure differential means lift.

Next time you watch an aerobatic plane flying, pay attention. You'll notice that the mean camber line - for a symmetrical airfoil, the centerline - of the wing is not parallel to the centerline of the airframe. It's angled down a few degrees in the rear, so that in level forward flight the airframe is parallel to the direction of travel and the wing has a few degrees of positive AoA. In inverted level flight, the airframe will be 'tail low' to the point where the airfoil is moving at roughly the same AoA as it was when not inverted. The airframe is tail low because the mean camber line and airframe centerline are not parallel to each other. In the real world, in inverted level flight, the ailerons will be trimmed slightly nose-down as well, which reduces the necessary AoA to keep the aircraft level. So the amount of 'tail down' attitude you would expect to see in level inverted flight would be slightly less than the angle between the airfoil centerline and the centerline of the airframe.

RE: Airplane wing ?

@enginesrus ... again, what theory do you support (since you deny the commonly held aerodynamic theory we all seem to support) ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

Quote (rb1957)

what theory do you support

The earth is flat
Perpetual motion is possible and being hidden by the oil companies
Alien beings are upon us in large numbers and even run the government
Lizard men rule the world ( and live in Denver international airport)
No one ever landed on the moon
Covid is caused by 5G masts
Birds can't fly ( they are surveillance drones)

Get the picture here?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Airplane wing ?

Quote (enginesrus)


Has anyone seen a flat wing airplane?

Google Sleek Streak.

Bernoulli theory and the air vectoring theory are not mutually exclusive. If an aircraft mysteriously does something to the air that generates lift, air has to be vectored downwards. I have worked out the behaviour of what I call a Bernoulli airfoil, flat on the bottom, with a circle section as the top surface. At zero angle of attack, it generates lift. Round off the leading edge (messing up my angle of attack model) and move the top of the curve forward, you have something that looks like a Clark Y airfoil. Particularly after they brought in cantilever wings in the 1920s, an airfoil section must do three things...

  1. ...generate lots of lift
  2. ...generate minimal drag
  3. ...function as a structural section.
My impression is that most of this stuff was worked out by guys playing with wind tunnels. CFD came along decades later.

--
JHG

RE: Airplane wing ?

Bernoulli airfoil ... sure it'll generate lift (at zero incidence) ... 'cause it has a curved camber-line (along the mid-thickness line). This was figured out in the early 1900s by a bunch of aerodynamicists (like Prandtl) supported by wind tunnels, then much later CFD.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

(OP)

Quote (3DDave (Aerospace))

A symmetrical wing at 0 degrees AoA produces no lift. To produce lift it tilts up to increase the amount of curvature above the stagnation point and decrease the amount of curvature below the stagnation point.

The tilting up in the front of the wing, allows for air pressure under the wing, that causes lift. If said wing had a box where no airflow was allowed over the top but only the bottom, in a wind tunnel, it would produce lift,(as long as turbulence was controlled,) when tilting up as mentioned.
My theory is simply based on logic.
A wing can be likened to a boat on a plane on water, skipping along on a higher pressure surface.

RE: Airplane wing ?

It would produce about 30% of the lift compared to allowing air to flow over the top.

RE: Airplane wing ?

(OP)
Take a flat blade ceiling fan, similar to a propeller, propellers don't suck the plane through the sky, they push it.


It would produce about 30% of the lift compared to allowing air to flow over the top.
Do you have wind tunnel data for that statement?

When a submarine uses its control surfaces it is the water pressure that is acting on them not a vacuum assist. Especially at say 2 mph or less.

When a bird fly's it uses its wings to bite into the air and push down creating a higher pressure.

RE: Airplane wing ?

It's been a while since I plotted the pressure distribution over a pressure-ported airfoil, but somewhere I think that I do, but similar data is widely available.

Back the fan blades with a disk and see what happens to the flow.

RE: Airplane wing ?

"My theory is simply based on logic" ... sorry, you can't say that, well not here you can't.

You've said our theory of lift is Wrong. I've asked you to explain your theory. "logic" is not a theory. Can you calculate the lift of a wing, not a fanciful shape, an actual shape.
Say you had a wing 10' long, 1' chord, say 4deg incidence, 100fps airspeed ... what lift would it generate ? Does anything else need to be defined ?

The motion of a bird's wing, and so how it generates lift, is very different to an airplane's wing. Although you can compare a soaring bird (where the wing isn't flapping) to an airplane. I would expect that in that case the soaring bird's wing has the same pressure distribution as an airplane's wing. Can you demonstrate your proposition ?

For a propeller, the "upper" surface suction and the "lower" surface pressure do generate thrust. "upper" and "lower" are defined by the rotation of the blade.

A submarine's fins are the same as an airplane's wings; they are typically (by observation) symmetric foils, which produce lift by incidence. what's this "vacuum assist" you talk about?

What's your point with "No airflow over a wing there causing a pressure difference." ? Are you saying that an airfoil (however you want it to be) sitting on the ground with no airflow around it, won't produce lift ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

Stop feeding the troll folks.....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Airplane wing ?

I came here for a good argument.

No you didn't, you came here for an argument.

Yes, but that isn't mere contradiction. An argument is a logical set of statements intended to support a proposition. Contradiction is merely the automatic gain-saying of whatever the other person said.

No it isn't.

...

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

My $.02. Newton is wrong... look at a vapor cloud on the top of a wing. Bernoulli is wrong... the air column does not create the opposing nozzle boundary (equal transit time does not exist!).

A wing curves the airflow around it because air is slightly sticky.

The curve acts just like the bend in a sheetmetal part. The wing is the neutral line of the bend. Everything above the neutral line puts tension in the material... or flow field. This has the effect of lowering the static pressure because its stressing the flow field ( or streamline if you need to think of it like that) out. Everything below the neutral line is in compression, thus causing an increase in pressure because the flow streamline is running into something causing it to back up because of the forced inflection. Back to the sticky part... Because it is slightly sticky that forces there to be a gradient between top and bottom... typically at the leading edge and trailing edge when we have decent air flow and its not separated (intentionally or not) Thus a well designed lifting wing puts most of the lower pressure on top, and higher pressure on bottom.

Fun starts when you start to go fast enough... again that little bit of sticky gets more important... you cant think of curvature anymore because you don't have time for that and you have to look at the instantaneous slope of what the airflow is hitting. If it's positive slope, you increase pressure and compress the flow field to the point of forming a shock wave. If it's a negative slope you loose pressure and get expansion.

Even more fun is when the curvature causes tension fast enough suddenly the air starts to care about instantaneous slope of what it's hitting.

How much one side does vs the other... (insert flight variables here). whichever side has the best PSI*SI wins.

RE: Airplane wing ?

ok, i'll bite ... is there a name for this theory or is it your own idea ?

"A wing curves the airflow around it because air is slightly sticky." ... does "sticky" mean the same as "boundary layer" or "viscosity" ? but then that is flow circulation theory.

"look at a vapor cloud on the top of a wing" ... do you mean the condensation that accompanies a shock wave ?

same as I asked the OP ... apply your ideas to a wing, and show how much lift it'll generate.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

Quote:

A wing curves the airflow around it because air is slightly sticky.

That's the description of the Coanda effect, isn't it? https://en.wikipedia.org/wiki/Coand%C4%83_effect That is supposedly the mechanism by which Bernoulli effect is helped out, through the momentum of the topside air flow being directed downward balancing the resultant lift

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: Airplane wing ?

Here is a photograph of a Junkers J2, the second cantilever aircraft ever built, minus its wing.


What we tend to ignore when we discuss early monoplane airfoils, is the requirement that the wing have an efficient structural shape. This aircraft had a 120HP engine, and a gross weight of 2500lb. The contemporary Sopwith Camel with similar power weighed around 1500lb gross.

If an airfoil is grossly asymmetric like this one, you can use Bernoulli's equation to calculate lift, and get a reasonable approximation. By World War II, people had tested airfoils in wind tunnels, and they had worked out shapes that were less asymmetric, that had good lift/drag ratios, and that were not analyzable by Bernoulli's equation.

--
JHG

RE: Airplane wing ?

contrast the thick mainplane, with the very thin (almost planar) tailplane. Of course the tailplane generates it's lift with down incidence and with a large elevator.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

(OP)
How is that over the top airflow at say 5 times the speed of sound?
Again fly your hand out a car window at 50 or so MPH. What is pushing up or down your hand, just feel it.


Why can't some have a discussion without the name calling? I've been here for years.

Quote (LittleInch (Petroleum) 28 Jul 23 06:52 Stop feeding the troll folks.....)



According to a fellow here the pressure reduction over the top of the wing only accounts for 2% of pressure differential lift.
https://www.avsim.com/forums/topic/4217-bernoullis...

Its the force from the forward movement and angle of attack that creates the high pressure under the wing. The main reason for a curve in the wing section is for the spar. So that 30% is wrong.

RE: Airplane wing ?

enginesrus,

You may indeed have been here sometime, but you started this post with "one simple question" which was answered some time ago ( now 31 posts later) and yet you persist in apparently ignoring all the responses and decades of theory established in experiments. Then you take one person on a thread which is equally non conclusive and just random people spouting unsubstantiated "theories" and say it proves whatever point it is you are trying to make - and I've got lost as to what that is.

So sure, your presumably flat hand deflects air down and there is a resultant force up or vice versa. However this creates huge amounts of drag which forces your hand backwards. If indeed you could make your hand the shape of a wing with a curved top surface and less curved bottom surface ( rather difficult) you would get the same effect, but less drag.

I remind you that this forum is a "Professional forum and technical support for engineers for Aircraft engineering."

I would strongly recommend to any other posters that they simply don't reply and let this thread die its natural and overlong death.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Airplane wing ?

(OP)

Quote (I would strongly recommend to any other posters that they simply don't reply)

Funny how some have no interest in learning something new.
Just do the search, the subject has been taught wrong even in college classes, its not just ME saying it.

RE: Airplane wing ?

Quote (enginesrus)

Funny how some have no interest in learning something new.

You never post 'something new'. Your posts are pretty much always either stumping for some random climate engineering conspiracy theory website, or 'asking questions' about very well known engineering or physics processes and then calling everyone idiots when their correct explanations don't make sense to you.

I, for one, and happy to see others besides me grow tired of it.

RE: Airplane wing ?

2
Hi all,

Here is a great video by a Boeing tech fellow on common misconceptions in aerodynamics:

https://www.youtube.com/watch?v=QKCK4lJLQHU

He goes over many fallacies in the conceptions of how lift works.

In actuality both the Newtonian and Bernoulli explanations are incomplete. Generally the Bernoulli "explanation" relies on the fallacy of equal transit times for fluid elements, and the notion of "stream tube pinching" both of which have no physical basis.

This video goes over the mechanics of lift in the most complete way I have seen.

Keep em' Flying
//Fight Corrosion!

RE: Airplane wing ?

Oh, no, not avsim vs actual data I actually saw on actual manometers. If a plank worked nature would have kept planks, like on insects in very low Reynolds number flow, and not gone to all the trouble of smooth airfoil shapes on birds.

The pressure increase under the wing is much smaller than the decrease on top. Mach flow changes that, but not enough below 0.8M to give up the nice curved wings.

Technically it's not possible to work out the performance of an airfoil by Bernoulli's equation because one needs to know the velocity distribution - that distribution is not a constant over the wing. You can look at the pressure distribution from testing and find the local airspeed, but no one cares, because the critical thing is pressure reversals which indicate stall and those are measured directly.

Even then, the majority of wind tunnel work doesn't bother with either one - they just create a lift, drag, and pitch-moment chart with respect to Angle of Attack, and normalize for dynamic pressure to use the coefficients in overall aircraft performance.

If anyone cares more they use smoke-streams added to see if the airfoil has unwanted or unexpected flow detachment; stall.

None of the rest is "new."

There are computational methods, such a panel flow, to get into the ballpark, and they compute airspeed from momentum and use Bernoulli's equation to generate the pressure distribution.

It's taught "wrong" because people continue to repeat bad explanations, often from the same seemingly plausible, but incorrect diagrams drawn by illustrators. Even from 20 year old zombie discussions from non-aerodynamicists. Be glad that "theory of lift" isn't what aircraft design is based on and that Bernoulli's equation, so useful in understanding incompressible flow, is simpler than what is required to deal with flow above about M 0.3 on up.

RE: Airplane wing ?

I have a really neat picture (somewhere !?) of a model of the EAP (what became the Euro-Fighter) in a water tunnel, with different coloured flow streams. very nice !

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

Doug McLean's presentation is very interesting. I will have to check out his book. I am certain much of it I will not fully understand. But his presentation is encouraging that I will be able follow his logic on the explanations of misreprentations, especially the equal transit theory.

RE: Airplane wing ?

Here are the few examples of a flat-wing 'aircraft' I could conceive of... fun toys... otherwise no practical value except for teaching children.

For hundreds of reasons... aerodynamically and structures wise for instance... flat wings and stabilizers surface have ZERO practical value... for starters.





We have all given enginesrus some good insights and comments and solid technical insights on this topic... from mature/practical perspectives as professionals... and all this appears to be swept-aside by the OP looking for 'Q-magic'.

NOW, lets get real... I have to concur with LittleInch... let's stop playing games with this obvious 'non-aero enginesrus' [engines Russia?]... and consider this an interesting discuss among ourselves...

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Airplane wing ?

"the subject has been taught wrong even in college classes"

Gosh oh gee, then why do Boeing and Airbus keep hiring grads from the Guggenheim schools, both of which companies (amongst other Western makers) keep making the highest performing aircraft in the world?

RE: Airplane wing ?

I read the OP as "engines are us".

We should understand that our theory of flight can be fundamentally wrong, and still produce valid results.

Consider gravity. Newton's view of gravity as a force has allowed us to send satellites into space, perform grav assist manoeuvres, and intercept a planet millions of miles away; a voyage taking years. But Einstein's Relativity theorises that this gravitational "force" is a manifestation of curvature of space-time. So Newton whilst being practically correct (correct in our "real" world) is fundamentally flawed. Another view is that Newton is correct, and Einstein is "just" explaining why the gravitational force is there in the first place.

Umm ... things are weightless in orbit, cause of the orbit dynamics, but things in orbit should be experiencing a lower gravitational "force" ('cause they're further from the Earth's surface). Gravity on the moon is 1/6th of Earth's gravity, 'cause the mass of the moon is less ('cause the curvature of space-time is less). I wonder how the curvature of space-time is away from the Earth's surface. At the Lagrange points the gravitational "force" of the Sun is balanced by the Earth ... does this mean that space-time is "flat" ?

It is possible (likely ?) that some new idea will come along that will change the basic theory of aerodynamics, but this should "condense" to our current theory in our real world (so that the difference is philosophical rather than practical) or else show that our real world is just a "lucky" co-incidence (and we have tuning factors that allow us to match the real world).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

At the Lagrange points the gravitational "force" of the Sun is balanced by the Earth ... does this mean that space-time is "flat" ?

Sure, if you can call the top side of a saddle "flat". Or, let's say it's flat for certain limits of flatness.

"It is possible (likely ?) that some new idea will come along that will change the basic theory of aerodynamics, but this should "condense" to our current theory in our real world"

Funnily enough, condensed matter physics at the bleeding edge is studying Bose-Einstein condensates, the most interesting examples of which are superfluids. In "real world aerodynamics" - somebody said lift happens because real world fluids are sticky (have viscosity). Helium below ~2 Kelvin is a "superfluid", i.e. has a vanishingly small viscosity and displays strange behavior (will flow up the wall of a container). Technically, you cannot have fluid dynamic drag or lift in a superfluid. Not sure if that has been experimentally confirmed, but I would love to get funds and build a superfluid helium wind tunnel so we can test it, you with me Rb?
https://en.wikipedia.org/wiki/Superfluidity

Fun stuff.

As far as a "single theory of flight", there really isn't one. There are patched solutions that work in general across the variety of flow regimes from very low Re and Mach no. (bumblebee flying) to the opposite extreme of space shuttle re-entry (very high Re and Mach). Very different maths used. And generally, there are few fully theoretical solutions of fluid flow problems, more usually it's a jumble of partial numerical solutions, a lot of scale model testing, and a fairly large chunk of real world testing.

RE: Airplane wing ?

yes, and that (multiple theories optimised for different regimes) indicates that we don't have a full understanding of the basic processes ... a unified theory of aerodynamics. But we do have a good engineering understanding of "everyday" aerodynamics

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

"we don't have a full understanding of the basic processes ... a unified theory of aerodynamics."

Hmm...not sure I'd go that far? We know (or think we do) the underlying equations (Navier Stokes), but the solution is not tractable (except in a few cases) with our current math capabilities. We have found pretty darn good approximations, and can link them back to the theory, so far at least. It's fun to see the direct NS solutions progressing year over year in the computational aero field.

RE: Airplane wing ?

Popular Mechanics magazine happens to have a story in the July/August 2023 issue that is about paper plane flight. It does not go into great detail but it says the flat surface of a paper plane wing develops lift differently than a standard airfoil; vortex lift is involved for the paper plane. A similar situation applies to flight of many items: Frisbees, birds, bees, tree seeds, etc. I did not see the actual article on the Pop Mech website but I do not have a subscription so it could be behind their paywall. I purchased a hard copy to read the whole story.

RE: Airplane wing ?

Good segue:
I'd like to see the OPs theory on how appropriately placed vortex generators on the upper surface,( or for that matter, divergent trailing edges, blown flaps), lead to real and measurable increases in lift.

Then he or she can present it to AIAA, NASA, Boeing/Airbus flight sciences...

Or maybe TSAGI.

Enjoy.

RE: Airplane wing ?

Ng2020...

"Or maybe TSAGI."?????

OK... I'll bite... what is 'TSAGI'??

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Airplane wing ?

from wiki ...
"The Central Aerohydrodynamic Institute (also (Zhukovsky) Central Institute of Aerodynamics, Russian: Центра́льный аэрогидродинами́ческий институ́т, ЦАГИ, romanized: Tsentral'nyy Aerogidrodinamicheskiy Institut, TsAGI) was founded in Moscow by Russian aviation pioneer Nikolai Yegorovich Zhukovsky on December 1, 1918."

will, you need to figure out this internet thing and goggle ... smile

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

Rb... Dohhhhh...

Ah... I see cried the blind man... Ng's reference to my [prior] 'Russian' reference... 2thumbsup

I was being a bit 'engineerdy' when I Googled TSAGI... and got TsAGI... DANG. I thot Ng was giving us a wink/nod with a contraction like YGBSM...

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Airplane wing ?

I was too late (entered USAF in 1973) to ever work a Wild Weasel aircraft, but once when some other pingers and I got in trouble during basic training for USAF at Lackland AFB, TX, our punishment was to wash and wax the F-105 Thunderchief on display in front of our barracks. At that time of course, I did not know about the Wild Weasels, or that the F-105 had been uses for Wild Weasels. And although I didn't know that YGBSM was their motto, YGBSM was what we all bitched when we saw the size of our punishment...but the YGBSM was voiced VERY quietly so the drill sergeant could not hear us.

RE: Airplane wing ?

GI's default-to-using the BAD/IMPOLITE names/contractions for 'things' and 'situations', etc...

79FS Wild Weasel mission patch...



Alas we are drifting-off-topic...

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Airplane wing ?

Nah, not so much. WW aircraft and pilots are always fun topics.

RE: Airplane wing ?

ah, back in a time when people could be sensible ... SNAFU, FUBAR ...

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

NASA's Glenn Research Center has introductory articles on aeronautics:
https://www1.grc.nasa.gov/beginners-guide-to-aeron...

Lift:
https://www1.grc.nasa.gov/beginners-guide-to-aeron...

Lift using Wright Brothers' airfoil in discussion:
https://www1.grc.nasa.gov/beginners-guide-to-aeron...

The false 'equal transit time' / 'longer flow path' explanation for the increased air velocity and low pressure on the top surface of a wing was very common years ago.

https://www1.grc.nasa.gov/beginners-guide-to-aeron...

I don't know if it is still used in modern texts but some science 'facts' are hard to eliminate being repeated even when there is extensive proof of their fallacy. Cases in point: female praying mantises always eating the male after mating, lemmings suicide, coriolis effect on bath water drains, etc.

Various other incorrect theories for lift are also discussed on the NASA GRC website. 'Skipping stone theory':

https://www1.grc.nasa.gov/beginners-guide-to-aeron...

'Venturi theory':

https://www1.grc.nasa.gov/beginners-guide-to-aeron...

RE: Airplane wing ?

Quote (Brian Malone)

The false 'equal transit time' / 'longer flow path' explanation for the increased air velocity and low pressure on the top surface of a wing was very common years ago.

The Bernoulli approach is still taught - but only (at least in my experience) at the introductory level before students are ready to be exposed to Navier-Stokes and more advanced compressibility solutions.

The uneducated seem to cry foul, but this is how all science is taught. Initially you learn basic concepts which are only true based certain basic assumptions which don't represent the real world. Once you understand those, you learn more complicated models.

RE: Airplane wing ?

enginesrus, OP, you often seem to be hell-bent on trashing degreed individuals and/or accepted and proven knowledge/technology but I am digging the discussion this thread has produced. I was not familiar with the flow turning and fluid compressibility theory of flight - it makes a lot of sense and captures all conditions of flight and not just specific regimes.

RE: Airplane wing ?

Then again - there is the exception condition of vortex lift . . . 😀

RE: Airplane wing ?

we have a perfectly good theory for every day flight conditions. We have special optimised solutions for uncommon regimes. I'm guessing the uninitiated don't appreciate the nuance and conclude if we don't have one theory for all then we have no theory ? But to say "I'm going to replace the entire theory that works well for everyday situations with what I feel on my hand and with logic" ... yeah, that flies in the face of professional engineering.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Airplane wing ?

One of the toughest things to wrap your head around as an engineering student - look at the wing root fillets on modern aircraft. Why are they there? You would expect to see more drag from adding cross section area in the flow direction? It's not really clear until you watch some wind tunnel video to see the flow results with varying amounts of fillet added. Interference flows are not an intuitive result, you really need to spend some time with the NS or Euler equations to see what's going on.

RE: Airplane wing ?

Quote (LiftDivergence (Aerospace)31 Jul 23 20:23
Hi all,

Here is a great video by a Boeing tech fellow on common misconceptions in aerodynamics:

https://www.youtube.com/watch?v=QKCK4lJLQHU)


Doug McLean starting at 7:58 "Same effect as if a continuous material was under internal stresses." That's how our FEA software works... bunch of mass-spring-dampers. To me its the same as bending sheetmetal. That's why I said what I said.

RE: Airplane wing ?

RoarkS, that's a great link. Another great quote in there at about 13:57 is from Spalart:

"It's easy to explain how a rocket works, but explaining how a wing works takes a rocket scientist."

Spalart was an aerodynamicist who (along with a colleague, Allmaras) came up with one of the simpler methods to model fluid viscosity in high speed (turbulent) flows. You don't come across his name unless you have spent some time doing CFD.

https://en.wikipedia.org/wiki/Spalart%E2%80%93Allm...

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