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You are currently reading a thread in /sci/ - Science & Math

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I recently got into a debate with an idiot about what makes airplanes fly. He expounded his belief in the correct answer which was completely wrong and despite my constant attempts to disprove his idea and indicate the correct one, he would not believe me. It seems that there is a strongly believed and widespread misconception about what makes airplanes fly. So, without giving away the real answer, I come to /sci/ to ask the general populous here what they think causes airplanes to stay aloft. Who thinks what and why?
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The magenta line in the pic.
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>>7837338
They accelerate fast enough to enter loe orbit
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>>7837340
Close but no cigar.
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>>7837338
Whenever you board a plane there is a pure mathematician also on board, usually acting as just another traveler.

This pure mathematician has an IQ that is over 300 and has a creativity and logic abbility that is unmeasurable so this pure concentrated brilliance makes the plane fly.

Of course, the mathematician is too busy writing his proof as to control the plane, which is why we got pilots which are trained specifically to manipulate the power of the mathematician's mind so that they give the correct direction and speed desired for the flight.

These pure mathematicians that work in planes usually start with a salary of 300k.
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I work as an airframe maintainer and everyone at work thinks it to do with differential pressure but im more convinced it has to do with newtons laws where the plane is oriented such that the angle deflects the fluid causing a net upward force
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Sky magnets pulling the plane up.
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From what I understand, an airplane generates lift from the difference in air pressure between the top and bottom of the wing. The air needs to move faster and farther along the drop than on the bottom, so the wing air pressure above is less than the air pressure below. The result is that the wings effectively "skim" off the lower air while simultaneously being sucked up by the semi-vacuum above
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>>7837344
you're an idiot. its to do with the coriolis force.
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OP Here

>>7837362
This is the correct answer.

>>7837364
This is the commonly believed incorrect answer.
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>>7837369
I think the prevalence of the "incorrect" answer is because both are actually correct, but to different degrees.

The shape of the air foil DOES generate a small amount of lift and make the plane slightly more efficient, but the MAJORITY is from the "angle of attack" letting the plane skim off the air. That's why an airplane can fly upside down for example.

Saying that air pressure differences doesn't exist at all and have an impact is also untrue.
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>>7837368
Then why do cars need spoilers?
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>>7837369

The pressure distribution on an airfoil causes lift. The air's momentum is altered, yes. But the mechanism by which air causes a force on the airfoil is pressure and shear. You can think of it either way.
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>>7837377
The pressure difference is negligible and even debatable if it even exists. The common statement is that the air travels faster over the top than the bottom thus creating lower pressures. But real field testing shows the air under the bottom can actually travel faster.

In either case, the air being directed down probably contributes 99% of the force or more.
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>>7837384
So everyone knows how cool you are.
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>>7837387
Then explain why airfoils are more efficient than perfectly flat wings
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>>7837396
Because airfoils are better shaped to direct air downwards. Flat wings can't direct air downwards unless the plane is tilted up very slightly which isn't generally a stable orientation of the plane.
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Newton's third law. As I've said in previous threads, there's actually an entire Wikipedia article on the subject.

https://en.wikipedia.org/wiki/Lift_(force)
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>>7837364
In what universe does this make sense.....

>>7837369
It fucking is?

Jesus fucking christ, I couldn't tell you the math or physics behind it, but I can grasp the concept without it being introduced to me. Just like people speak their language with great levels of proficiency without knowing what all the cooky names for each 'part of speech' that some nerds in a basement cooked up to try and explain something.

POINT BEING, In what fucking universe do people perceive a sucking motion when the plane flies?
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>>7837362
>I work as an airframe maintainer and everyone at work thinks it to do with differential pressure but im more convinced it has to do with newtons laws where the plane is oriented such that the angle deflects the fluid causing a net upward force
It's both. The shape and angle of the wing with relation to the airflow causes the airflow to redirect, which results in differential pressure on the wing as the equal and opposite reaction to the wing redirecting the airflow. Make sense?
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>>7837364
>The air needs to move faster and farther along the top than on the bottom,
That's the myth (often taught in schools)..
Flying wings like the B2 actually have the curve on the bottom.
The real key is the angle of the wing. As long as the front is a little higher than the back air "piles up" under the wing, creating a high pressure area,
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It's basic physics
you generate lift by displacing air downwards
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I used to think it was because the air was pushing directly onto the bottom of the wing
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>>7837369

I'm a NEET but incredulously I believe that I know more about airfoils than most on this board simply because as part of my interest in RC aircraft I have spent a solid year studying nothing but airfoils and propeller thrust as opposed to say an undergrad who skimmed over it in a few lessons. Anyway lets not argue about that just listen to what I have to say; The short answer is that it's Newton's 2nd Law. I know this because I can calculate lift to over 80% accuracy using purely an application of that law. The long answer is that there is an additional component arising from the curvature of the airfoil cross-section. I know this because a wing will still generate some lift at zero angle of attack. However the Bernoulli explanation is bullshit, there is no maths to back it up, it's just an explanation that seems to make sense when you say it out loud. The additional lift is generated by the streamline curving. If you solve the Euler Equationsand by extension the Navier-Stokes Equations for curved flow you get the result

dP/dr=(rho*v^2)/r

As you can see, increasing the radius of curvature, r increases the pressure differential, dP/dr. This can be seen in hurricanes, the eye is low pressure no? I have studied the Euler Equations it is true.

The final piece of evidence is that ducting a propeller not only increases it's thrust but causes it to be dynamically stable. The thrust increase can be explained away by the prevention of tip vortex losses but the stabilization can only be explained by the creation of low pressure over the lip of the duct which causes the underside to float on a ring of high pressure.

So to summarize, it's mostly just reaction thrust but there is some lift from a pressure differential.
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>>7837362
Yes, that's called angle of attack, but it's certainly not the main cause of lifting force. If it were, then the roofs of houses wouldn't fly up during high winds.
Most houses have angled roofs, and even if the winds are passing perpendicular to the peak of the sloped roof, creating a force downward (as seen in pic related), they still go up.
This is because the pressure pushing up on the roof (~14 psi) from inside the house is far greater than the pressure above the roof, which is being mitigated due to the extreme airflow. The pressure differential creates a net force upward, and if the differential is great enough, the roof flies up.
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>>7837477
This would imply that houses are air tight or wind speeds are changing insanely rapidly.

Name field checks out.
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>>7837479
He is right, if you want a citation see my post above his.
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>>7837477
Yeahh... No
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>>7837479
It's readily available information, I didn't feel like a citation was necessary for something that I'm confident a 2 second google search would yield results for.
As a secondary citation, since you seem to be arguing against the very notion that roofs fly off in heavy windstorms, I urge you to literally just look at the picture of the aftermath of a tornado, or hurricane.
Anyway, even without houses being airtight, the differences in pressure are still enough so that the structural integrity of the roof must be compromised. That much you can't deny. And it doesn't imply anything about the velocity vector of the wind, simply that the velocity is great enough to create a pressure differential.
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>>7837515
None of this indicates why planes fly though. Regardless of pressure differentials on roofs, planes fly because of Newton's laws, not pressure differentials.
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>>7837517
For fucks sake man, do you know how frustrating it is to see a mongoloid arguing with someone who is trying to tell you something that I explained clearly in a post in this thread is? Like I spewed out all that info and nobody read it, they just continued to spout bullshit. Read my fucking post here I'll link it to you >>7837464
there is the fucking equation right there that tells you curving a streamline causes a pressure differential. Seriously fuck this board, full of pseudointellectual dickheads.
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>>7837517
are you fucking retarded? pressure and force are the same thing
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>>7837517
But that's not a complete model for aerodynamics. A plane can maintain a horizontal flight, with a descent far lower than would be expected of something undergoing purely newtonian forces, being gravity and whatever vertical drag is being supplied by the wings.
A plane would have a far faster descent were its wings to be simple slats rather than shaped wings.
The force from a pressure differential is very observable and if it weren't, then generations of aerospace engineers wouldn't agree that shaping wings on efficiently designed aircraft was a priority.

>>7837527
I saw your post after I had already made mine, sorry about that, but I do know that frustration, friend.
You're probably far better qualified to actually be explaining this anyway, I haven't taken any kind of engineering/physics course for 2 years
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>>7837364
>The air needs to move faster and farther along the drop than on the bottom
There's no reason for the air to move over the top in the same time it takes to move under the bottom, and in fact the air usually takes less time to move over the top. There is a speed difference, but it originates via friction with the trailing edge of the wing.
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>>7837537
More details:
https://en.wikipedia.org/wiki/Kutta_condition
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>>7837533
My rant wasn't aimed at you it was aimed at the guy who won't believe your roof analogy but yeah thanks for understanding. I don't know why I browse this board it's so frustrating.
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>>7837544
I used to go to /x/ for scientific discussion before I knew there was a /sci/ board
this place is significantly better, and sometimes I'll find a gem like you hiding in the sands of jargon-spouting gender studies students.
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>>7837544
>I don't know why I browse this board it's so frustrating.
because you are a worm who cannot achieve anything in his life. go in bar, try to be noticed by a girl and eat her pussy. do not try to be something that you are not.
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>>7837387
Pressure *is* force per unit area -- no pressure difference, no lift.
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>>7837362
so you are saying that you cannot explain how a plane flies outside galilean relativity ? do you have an explanation in GR ?
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>>7837547
>/x/ for scientific discussion
Really? The few times I've been there it's been all demons.
>sometimes I'll find a gem like you
Aww thanks, that's the nicest thing anyone has ever said to me on 4chan.
>>7837548
>Going to a bar for sex
That's retarded, go to a brothel, it actually works out cheaper. Let's do the maths:
>Go to bar every night 7 days a week
>£10 entry fee + £10 taxi + £20 drinks
>£40 a day
>Get lucky say twice a week
>(40*7)/2 = £140 cost of sex
>Go to brothel
>£30 cost of sex
£110 cheaper.
>>
u nigs be wrong. kek'd
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>>7837553
"scientific discussion" may be strong wording for what actually happened.
Basically I ended up being the person who would try to explain phenomena scientifically, and ended up being called a government shill 90% of the time.
I swear some of them think that the entire basis of our understanding of mathematics and science is a conspiracy carefully crafted by lizards.
As for being nice, I guess I'm just the only one not in a foul mood.
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>>7837561
That's the problem, everywhere is polarized. /x/ dismisses the scientific method and /sci/ dismisses anything not mainstream
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>>7837362
>I work as an airframe maintainer and everyone at work thinks it to do with differential pressure but im more convinced it has to do with newtons laws where the plane is oriented such that the angle deflects the fluid causing a net upward force

they are both right. lift coefficient scales linearly with angle of attack. but drag coefficient scales exponentially. thats why we do simulations and wind tunnel shit, because where the two meet is when your plane stalls.
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>>7837527
>this fucking thread

/sci/ is apparently full of retards man, don't let it get you down.
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>>7837583
not retards. just sophomores and freshmen. most people take fluid mechanics in junior year.
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>>7837582
this
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its a combination of bernoulli principle and what op thinks (newton drag?)... depending on the plane design preferences and what the pilot is doing (i.e. landing, takeoff, maneuvering, etc.)

but the lowest drag/most efficient setup (i.e. cruising) would try and balance only the bernoulli force with gravity with minimal cross sectional area perpendicular to the direction of travel (drag).

in other words, op troll fail, or is a dumbass.

a simple google image search of wing design gives the correct answer.
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>>7837605
It's nothing to do with the bernoulli principle
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>>7837642
welp, better call up every engineering firm that does CFD and tell them they are doing it wrong.
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For my part, when young, I thought it was angle of attack. In a later mechanics class I was told it was higher speed over the wing creating vacuum. Believed that for 20 years. Want to shoot that engineering lecturer now. A pox on them all.
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>>7837642
engineers: theyre into engineering. they design engines.

why arent people who design rockets called rocketeers instead of rocket scientists?
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Everywhere are thousands of little Master Yodas thinking theyre lifting the X-Wing but its actually just a plane

Over the years we have managed to train these Yodas into the flight paths we know and love today. Some Yodas have been specialised for military purposes and are a required fitting on modern jets.
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>>7837377
>>7837369
A passenger airbus won't fly upside down. Stunt planes and such are lightweight and go very fast which is why they can support themselves with just the angle of attack
A 747 needs flaps at low speeds.
You
Fucking
Self-righteous
Twat
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>>7837736
its not the bernoulli force

its just the force

use the force
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>All these people claiming pressure differential is somehow an invalid explanation or is outright false
Just stop. Both are entirely true (with the exceptions of the equal times fallacy and that surface curvature is necessary for lift). A wing DOES produce lift by deflecting airflow in accordance with Newton's laws (see circulation theory/Prandtl lifting line theory), AAAAAAAAAND there exists a pressure differential between the top and bottom of the wing (see thin airfoil theory). Not only are both contributing to the phenomenon of lift, but in fact both are FUNDAMENTALLY RELATED, as the airflow cannot be redirected without some variation of pressure; nor can a difference of pressure exist in an open system without flow being accelerated/redirected.

BOTH EXPLANATIONS ARE VALID.

>>7837443
It's not a myth, per se, but it's incorrect to attribute lift directly TO the difference in air speed between the top and bottom. It's more accurate to say the difference in speed is a BYPRODUCT of lift. If you're producing lift by deflecting air, the top surface of the wing WILL have lower pressure than the bottom surface, and by Bernoulli's principle, the air on top will be traveling faster than the air on the bottom as a result.

>>7837461
It's not entirely wrong to think that. Air "pushes" on all surfaces of the wing, but since the wing is angled and/or cambered causing air to be deflected, the pressure on the bottom surface is greater than the pressure on the top surface.
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>>7837775
ya whatever man,

your just a god damn know nothing engine scientist arent you.
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>>7837731
they're called aerospace engineers
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>>7837338
thanks dude, i've read this and fixed my mind
http://www.allstar.fiu.edu/aero/airflylvl3.htm
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>>7837338
bernouli's principle
because of the geometry of the wing while the craft is in flight air above the wing takes a longer path than air below.
this causes an increase in velocity, which constitutes a decrease in preassure.
the result is a preassure differential between the region below and above the wing.
this differential means the air on the bottom tends to expand upward catching the wing along with it, not unlike how a sail catches wind
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>>7837780
imo, really the only people worthy of being called engineers are mechanical engineers.

none of the other types of engineers work on actual engines. its all shinaningans, see.
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>>7837338
God loves us so much he lifts airplanes into the air and carries them to their destinations, except when there are naughty people on board (he drops it then).
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>>7837801
because electrical engines don't exist.

you're also clearly not an engineer yourself otherwise you'd realise that modern combustion engines have a fuck tonne of electrical features that MEs would be completely unable to design.
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>>7837775
>the air on top will be traveling faster than the air on the bottom as a result.
this alone does not explain the contribution to the lift though. how do you turn a different velocity into a force ?
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>>7837841
>this alone does not explain the contribution to the lift though.
Well, not very explicitly, no. That's why I said it's more of a byproduct than anything else (though, through the principles of fluid mechanics, if you have the velocity flowfield you absolutely CAN still derive the pressure field and aerodynamic force from it).
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Is it just me or is this copypasta?
>>
Bernoulli's venturi effect combined with Newton's 3rd law. There's a reactive force combined with a generated low pressure environment on top of the foil. There's a trade off in lift per speed, in the sense that the tensile modulus of the wing surface can not handle the drag coefficient of high-lift/high-speed. Impellers and turbines work on the same principles.

Also turbulence in aircraft is usually due to atmosphere barometric change in air pressure around various lifting surfaces of the vehicle, combines with the change of relative speed in head-wind.

https://www.youtube.com/watch?v=bAfqqC1AFCU
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>>7837338
>a debate with an idiot
"Never argue with an idiot. They drag you
down to their level, then they'll beat you
with experience."
– Jack Coleman-Levy, UIC
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>>7837939
>the tensile modulus of the wing surface can not handle the drag coefficient

Materials fag here, can you explain more? It sounds like you are suggesting the mechanical properties of the composites used for wings are the limiting factor in aeroplane speed?
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>>7837348

..don't forget the passenger belief factor. The very belief that the plane can and will fly causes the quantum waveform to collapse in a favourable way for the plane to stay in air.
>>
Shall we now proceed to argue why a bicycle stays upright ?
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>>7837990
It's because of the rotational inertia of the wheels, right?
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>>7837369
>airfoils do not generate lift at 0° angle of attack :^)
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>>7838153
Airfoils push air downwards at 0 angle of attack.
>>
This thread perfectly highlights the fact that most people post in threads without reading the previous replies.
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>>7837369
https://www.youtube.com/watch?v=0ul_5DtMLhc
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>>7837369
Both are same.
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>>7837384
to let people know that you vape
>>
It just works
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>>7837338
Angle of attack mainly, not Bernoulli principle as many assume.
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>>7837829
no, im not an engineer.

but i bet you are!

lol
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>>7838173
only some do. go look through the NACA database and you will find plenty of flat bottomed airfoils that generate lift.
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>>7837338
the bernoulli vs defelection debate... lol

they are both correct, both will help you fly.
the airfoil is more efficient by far however.

for those who deny bernoulli please explain the Magnus effect
https://www.youtube.com/watch?v=QtP_bh2lMXc
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>>7839068
The Magnus effect has nothing to do with Bernoulli, it's caused by the redirection of the air not by a pressure differential.
>>
https://youtu.be/XWdNEGr53Gw?t=14m22s

Bernoulli's venturi principle, and newton's second and third law.

In relative head wind, propagated by the thrust of the propulsion system, a faster flow is diverged over the wing. This creates lift, proportional to the pressure differential of the upper and lower wing surfaces.

The reason a plane is able to take off a treadmill is that the tires act like sleeveless bearing, and the prop engine is pulling the plane forward, generating that needed relative head wind.

If you had zero friction, you could bolt a house fan on a 1 ton block of granite and have it incrementally move forward. Than again, there's no such thing as zero friction, even in the vacuum of space, where it really is negligible.

The reason it isn't solely the angle of attack is that the wing is not designed to resist the forward thrust of propulsion. The propulsion system is there to lurch the aircraft forward with enough speed to create a pressure difference to create enough upward force to defeat the downward force of gravity.
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if you retards would just learn how to do airfoil velocity triangles you'd understand the difference between reaction and impulse.
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>>7837775
>it's incorrect to attribute lift directly TO the difference in air speed between the top and bottom. It's more accurate to say the difference in speed is a BYPRODUCT of lift
Change the velocity of a fluid and the pressure will change (pic related). On the other hand, a pressure that differs from what you'd predict from the velocity field is carried away rapidly as sound waves.
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>>7837338
Aerospace engineer here

Lift is the name given to all forces which push a body "up". Usually, in mechanics of flight, a body fixed coordinate system is used to enforce this condition. The geometry of aerofoils is designed to maximize this effect. You can easily derive the relevant results at a very preliminary and rough level yourself by learning complex potentials and the Joukowski transform coupled with control volume analysis. The pressure coefficient distribution across the surface of an aerofoil dictstes its life characteristics and the bottom line is that pressure below>pressure above which means net force upwards is produced.

However, other parts of a conventional aeroplane generate these forces as well and it typically takes CFD simulations to find the exact magnitude of these effects due to our inability to solve the Navier Stokes equations analytically.

Your friend is a crackpot.
>>
>>7838153
>>7838173
Cambered aerofoils generate lift at 0 degrees AoA
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>>7837338
Airfoils generate lift because they divert air downwards at an angle of about 10*. They change the direction of the air because of the angle of attack. If the air hits the airfoil at an angle then the airfoil will scoop through the air and because vacuums are impossible air has to fill the space behind the wing. The air tries to follow its surface and it does, although the pressure will be much lower on the top. If the angle is too great the air will not be able to follow the surface and will begin to tumble and spin which removes lift. We call that "stall".

TL;DR air moves down after the wing and that's what makes the wing go up. Newton's third law + Coanda effect + no vacuums are allowed
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>>7837362
None of them specifically , as you couldn't lift 30 kilo plane with it. But I heard something about some kind of spins that happen on the upper side of the wing, which contribute to total lift. Also, aerodynamics is a bitch.
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>>7837338
>>7837362
>>7837364

if that is true explain this
https://www.youtube.com/watch?v=kNWfqVWC2KI
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>>7839263
if one side was actually a higher pressure in this diagram, it would push whatever is in the bottom out.

This lower pressure shit is just an old meme, lift is generated by pushing air downwards
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>>7837841
Bernoullis principle
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>>7838153
The datum used for an airfoil is kind of arbitrary (the chord line is usually used, but not always), and therefore "zero AoA" is equally arbitrary. Every airfoil DOES, however, have a zero-lift axis, which - if used as the datum - does obviously make that statement true.
>>7839149
Redirection of air can only occur if there's a pressure differential. You're wrong to assume they're mutually-exclusive.
>>7839264
Technically lift is the net component of aerodynamic force that is perpendicular to the (far-field) air velocity vector. It needn't be necessarily "up," it can also be centripetal or potentially in any direction perpendicular to the object's motion. Even drag can be "up" if the object is descending vertically, as with a parachute.
>>7839541
>if one side was actually a higher pressure in this diagram, it would push whatever is in the bottom out.
Except no, because gravity.
>>
Does the layman really not understand how significant the angle of attack of a wing is? How would they explain how a propeller works? Or a helicopter. Shit I had this figured out at 13 making airplanes and helicopters with functioning swash plates in fucking gmod
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>>7839612
>How would they explain how a propeller works? Or a helicopter.
The old equal-transit fallacy could still "explain" for those, since both still have airfoiled blades (and the layman wouldn't know that a helicopter rotor uses symmetrical profiles). The better question is, how do these people think paper airplanes work?
>>
>>7837605
>>7837939
>>7839068
It's not a combination. Both the lift calculated from Bernoulli's principle and the lift you'd calculate by seeing how much air is deflected downward individually equal the entire lift on the plane. Angle of attack is not a separate thing from Bernoulli's principle, it is included. Changing the angle of attack changes the speed difference between above and below the wing.
>>
>>7839631
>Angle of attack is not a separate thing from Bernoulli's principle

yes it is. bernoulli's is a oversimplified conservation of energy balance. angle of attack deals with conservation of momentum and impulse.

look up what a half reaction turbine is.
>>
>>7839655
>bernoulli's is a oversimplified conservation of energy balance.
It neglects viscosity but is a good approximation in this case.

>angle of attack deals with conservation of momentum and impulse.
If you think a wing at zero angle of attack can generate lift without deflecting air downward, you're just fucking wrong, mate.
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>>7839631
>It's not a combination. Both the lift calculated from Bernoulli's principle and the lift you'd calculate by seeing how much air is deflected downward individually equal the entire lift on the plane.

>It's not a combination.
>combination

>Both the lift calculated from Bernoulli's principle and the lift you'd calculate by seeing how much air is deflected downward individually equal the entire lift on the plane.
>Both... equal the entire lift
>Both

failing to comprehend the definition of combination...
== priceless ==

here's a goodie for you
https://www.youtube.com/watch?v=POHre1P_E1k
>>
>>7839686
Both individually. You don't fucking add them together.
>>
>>7837338
add enough thrust and anything can fly, add the right aerofoil shape and it just werkz, duh. 100000 hours in ksp
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>>7839676
>If you think a wing at zero angle of attack can generate lift without deflecting air downward, you're just fucking wrong, mate.

did you not read what i just said? i never claimed anything of the sort. the ratio of impulsive/reactive forces is a real thing in fluid mechanics. a good example of a device with an R of ~1 is a pelton wheel. the R value of airplane wings is dependant on the angle of attack, and while it can never be zero, it can be pretty close.
>>
>>7837348
Dude... can I get the number of your dealer? Holy fuck.
>>
>>7839705
Let me clarify: If you think a wing at zero angle of attack can generate lift without imparting downward momentum to the air precisely equal to the lift on the plane, you are fucking wrong.

You are also wrong if you believe that the lift calculated from Bernoulli's principle does not depend on the angle of attack.

If you claim there is some important lift-generating mechanism in airplanes due to effects neglected in Bernoulli's principle, feel free to explain it, but "reaction forces" / "conservation of momentum" is not such a mechanism. Bernoulli neglects compression and viscosity, not the third law.
>>
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>>7837434
I agree with this f-a-m. This is my type of f-a-m.

He understand that one doesn't even need to know physics/chemistry to understand why stuff is the way it is and how it interacts. It's innate to us humans.

As an example, you don't need to know that matter is negatively charged because of the excessive amount of electrons, it's just purely logical to us that there has to be something that causes matter to be positively or negatively charged, an existing imbalance of matter, particles, electrons call it whatever... and the function of science is to unlock that innate understanding we all possess.
>>
L = (1/2) d v2 s CL

/thread
>>
>>7839776
>conservation of energy = conservation of momentum.

okay buddy.
>>
>>7839802
Conservation of energy and conservation of momentum both apply simultaneously. They're not separate effects that you have to add together.
>>
>>7839784
>threading his own post
>>
its because the speed of the plane is greater than the rate at which is falls back to the earth. imagine this - throwing a baseball really far and eventually its going to fall? but what if you throw it so hard that it never has to reach earth, based on the gradient of the ground. eventually, the curve of the earth and diagonal fall of the baseball will become parallel, keeping it in the air. it all has to do with a galileo and huygens discovery in the 18th century by the way.
>>
>>7839806
yeah they are. static pressure and dynamic pressure are governed by different parameters. the shape of an air foil changes the static pressure of the fluid while its camber angle and angle of attack change the momentum.
>>
>>7839824
They are not. If you think the downward deflection of air equals only part of the lift on the plane, then I look forward to seeing your memedrive.
>>
>>7839808
I answered the OPs question thus /thread.
>>
>>7839836
>Who cares how lift works? Let's just take it as a first principle.
>>
>>7839834
then how does a pressurized fluid at zero velocity impart a force?
>>
>>7839840
If the fluid stays at zero velocity, there is another force keeping it from moving.
>>
>>7839847
that didn't answer my question.
>>
>>7839855
It is the generally true answer to that question. If you want to be more specific, get more specific.
>>
>>7839861
fluids can be not moving and have a pressure differential. this pressure differential can push on the bottom of a wing and is completely independent of whether the air is deflected downards. its a change in the energy of the fluid, not a change in its momentum.
>>
>>7839880
Well, that's wrong. An airplane always has downwash equal to its lift.
>>
>>7839885
and lift has two components.
>>
>>7839895
I'm sure you can break lift up into components somehow, but "lift predicted by Bernoulli" and "lift predicted by downwash" are not components; they are each the whole thing.
>>
>>7839900
downwash is 3 dimensional, and has a component caused by that static pressure differential. the high pressure air is on the bottom and is trying to flow to the top, and because of vorticity is directed downwards. downwash is the sum of that plus the air that is directed downward off the trailing edge of the wing.
>>
>>7837338
Bernoulli's principle
>>
100% guarantee its magic. Prove me wrong
>>
why is this thread still alive
>>
>>7839948
You're the one suggesting, prove yourself right.
>>
>>7837405
Bernoullis law
>>
By displacing air downwards you also create differential pressure, right?
It's one of newtons laws/ pressure or both of them
>>
>>7837464
damn, should have stopped reading here
>>
>>7838437
what a good show
>>
>>7840196
FYI that's a crackpot post; it is most certainly possible to do the Bernoulli calculation.
You can do the "rough version" suggested in >>7839264 yourself.
>>
>>7837338
Not an aero dude, but I've heard that the Bernoulli explanation isn't accurate. Moreso it's just the angle of the wing causing downward deflection of air -> conservation of momentum keeps the plane up. This would explain why planes can fly upside down, since they can move the ailerons to redirect flow.

Aero is dope and I wish I knew more. I'm a MechE though
>>
>>7838223
You're describing perfectly the principle of content vacuum pressure troll thread lift. Bullshit is lighter than meat. This difference drives lighter copypasta and troll threads up the board, while driving denser discussion threads down to page 10.
>>
>>7840206
ok... probably jumped the gun on that shit. Do aerospace engineers use Bermouli? That would solve a lot here
>>
>>7839311
>Coanda effect
>>
>>7837338
*assuming incompressible flow
air does indeed end up traveling faster under the wing than above it, resulting in a decrease in dynamic pressure and an increase in static pressure, providing lift, according to bernouilles equation or however you spell that.

Angle of attack plays a major role, which is why symmetric airfoils are possible, but even then it's mainly pressure differentials caused by a changing camber line. I don't know who put the idea in your head that pressure is not part of flight, but they were wrong.

Of course, in incompressible flow all bets are off, I think lift at that point is mainly generated by shockwaves.
>>
>>7840236
No, we don't. At distances away from an aerofoil, we use isentropic flow equations. Near an aerofoil, you have to go balls deep and use Navier Stokes to find the flow field, but if you just want to calculate, say, lift, you can calculte it to a very high degree of accuracy using Prandtl-Meyer shock expansion theory.
>>
>>7841337
How much of the lift on a typical passenger jet comes from effects that are thrown out by v << [math]c_{sound}[/math] approximations?
>>
>>7841371
v<<c assumption is usually made to assume incompressible flows. This will be extremely off, considering the effects of compressibility usually start being considered in aerodynamics at around 0.3 Mach number. A typical passenger jet cruises at M=0.85.

Typically, at these mach numbers, shockwaves can form on aerofoils which makes even Bernoulli and all the related isentropic equations etc derived from it useless due to the existence of non isentropic nature of shockwaves. These flows basically necessitate CFD or Prandtl-Meyer Shock Expansion theory
>>
>>7837368
>>7837344
This is actually the same thing you guys are talking about
Thread replies: 144
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