No One Can Explain Why Planes Stay in the Air

Dont the both theories contribute to the generated lift? I guess one could argue about the ratio, which principle generates more lift, and how much more.
 
If nobody knows why planes stay in the air how is it that they can design aircraft to do so? (And seriously? Aircraft stay up because they force air down.)
 
This is like saying we don't understand why billiard balls behave as they do. Of course we do, to a point, but what we don't yet understand is where the masses of the particles originates from that form atoms and molecules. The Standard Model still requires physicists to manually plug into the equations the masses that are found to exist via experiments. No proven theory yet explains mass. Higgs is a good attempt.The same forces that explain billiard balls explains air molecules on the bottom of a lifting surface pushing it upwards. Newton, Lagrange, and Hamilton rule classical mechanics. If you want to get philiosphical about mass and momentum and acceleration then start reading Mach. Fluid mechanics is why airplanes fly... Little tiny microscopic billiard balls on the bottom of wings push the wing up. L=T-V. Derivable from simple calculus and using Newtons f = ma.
 
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As an aeronautical engineer, we do know why airplanes fly. There are multiple ways of analyzing them, but it isn't F***ing magic. I really hate stupid articles like the one referenced. Apparently the people who wrote the article don't know a damned thing about circulation, or the Kutta-Jukowski theorem. Different "approaches" offer different data based on what is being sought; as they noted, Bernoulli and Newtonian Mechanics. They're both valid. They could also perform a Trefftz plane analysis,etc.

BTW, for simplicity, think of it like this. F=MA. The airplane stays up by throwing air down. Equal and opposite reactions. The different mathematics/physical approaches are just to reveal different data sets based on what we're seeking to understand about the vehicle's performance.
 
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My intermediate fluid mechanics TA said that if someone asks for a simple one word answer to describe, it's "circulation". I guess in the context of Kutta-Joukowski he's not wrong...

Still remember having to do those lifting line theory derivations. Good times.
 
Sundog said:
As an aeronautical engineer, we do know why airplanes fly. There are multiple ways of analyzing them, but it isn't F***ing magic. I really hate stupid articles like the one referenced. Apparently the people who wrote the article don't know a damned thing about circulation, or the Kutta-Jukowski theorem. Different "approaches" offer different data based on what is being sought; as they noted, Bernoulli and Newtonian Mechanics. They're both valid. They could also perform a Trefftz plane analysis,etc.

BTW, for simplicity, think of it like this. F=MA. The airplane stays up by throwing air down. Equal and opposite reactions. The different mathematics/physical approaches are just to reveal different data sets based on what we're seeking to understand about the vehicle's performance.
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I remember reading the way a plane fly is more by being "sucked" up by the depression created above the wing by the forward motion than by the pressure under it (pushing air down). Did I understood correctly what I was reading :) ?
 
galgot said:
Sundog said:
As an aeronautical engineer, we do know why airplanes fly. There are multiple ways of analyzing them, but it isn't F***ing magic. I really hate stupid articles like the one referenced. Apparently the people who wrote the article don't know a damned thing about circulation, or the Kutta-Jukowski theorem. Different "approaches" offer different data based on what is being sought; as they noted, Bernoulli and Newtonian Mechanics. They're both valid. They could also perform a Trefftz plane analysis,etc.

BTW, for simplicity, think of it like this. F=MA. The airplane stays up by throwing air down. Equal and opposite reactions. The different mathematics/physical approaches are just to reveal different data sets based on what we're seeking to understand about the vehicle's performance.
Click to expand...

I remember reading the way a plane fly is more by being "sucked" up by the depression created above the wing by the forward motion than by the pressure under it (pushing air down). Did I understood correctly what I was reading :) ?
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So you're saying that vacuum can do work. No, vacuum by definition cannot do work. "Nothing" is not capable of work. There are quantum properties of vacuum in the microscopic realm that do not apply to macroscopic objects. In the world of every day objects it takes "something" to perform work.
 
Like @Sundog wrote above, lift is also a funcion of Newtonian physics, it's just a little bite harder to calculate the lift of a wing than calculating the lift of a rocket. By determin the circulation, a way was found to calculate the lift out of a wing profile (2d) or wing geometry (3d), but that doesn't deny, that air is beeing pressed down and creates lift. This method was uses allready many decades ago with analog computers and maybe even hand manual calculations.

You can calculate the pressure distribution on the walls of a rocket nozzle (Laval) and add the force chamber pressure in the entry area to determin the lift of a rocket. If you do it right, it gives the same result as F=m*v (m for massflow, the should be a dot on it....). So there is no contradiction if two ways give the same result.
 
The bumblebee can't fly but he doesn't know it.

It's not possible to build a bomber faster than fighters, but a guy who didn't know it built the D.H. Mosquito
 

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I do have one question which I never got answered.
So, the wing redirects the air around it and throws it at an angle, somewhat downwards, which means there's a certain vector of force in the opposite direction, creating lift.
What I don't understand is this: how does the wing throw the air? I don't mean the redirection of the air to go downwards, that part I get. I What I don't get is how does the wing "hold" the air and how does it throw it? To my logic, the air happens to be around the wing.
Like... I get the situation where a spaceman in outer space throws a rock and that results in his movement in opposite direction.
I get the situation where an engine spews out mass and that moves the engine in opposite direction.
But both of those examples have the propellant mass held by the subject.
In the example of the wing, I don't see how the wing actually acts on the air around it to such a degree that it holds it and throws it.
If the air was going through the wing somehow, instead of around it, then i guess it'd make more sense to me. But with the air going all around it, my brain can't fathom the forces and connections between objects and molecules. For me, the air is like a board on the sea. When the sea moves, the board moves with it. Not in the opposite direction of it. Now if there was someone on the board paddling, actively moving sea mass behind, then I get it. But the wing is passive. Like the board. It doesn't do anything. Can someone help explain that?
 
MihoshiK said:
Everybody knows that in the case of the A-10, it's because the plane is so badassed that the air moves out of the way.
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Eureka ! The A-10 is Chuck Norris turned airplane (Chuck Norris can morphe into any object he want, because he is polymorph Chuck Norris: beating matter into submission with just a raised eyebrow, menacing stare).
And this solves the mystery of lift: its just Chuck Norris having fun with Newton and Bernoulli ghosts.
 
More seriously: most interesting part is that

This means that there are four necessary components in McLean’s explanation of lift: a downward turning of the airflow, an increase in the airflow’s speed, an area of low pressure and an area of high pressure.

But it is the interrelation among these four elements that is the most novel and distinctive aspect of McLean’s account. “They support each other in a reciprocal cause-and-effect relationship, and none would exist without the others,” he writes. “The pressure differences exert the lift force on the airfoil, while the downward turning of the flow and the changes in flow speed sustain the pressure differences.” It is this interrelation that constitutes a fifth element of McLean’s explanation: the reciprocity among the other four. It is as if those four components collectively bring themselves into existence, and sustain themselves, by simultaneous acts of mutual creation and causation.

There seems to be a hint of magic in this synergy. The process that McLean describes seems akin to four active agents pulling up on one another’s bootstraps to keep themselves in the air collectively. Or, as he acknowledges, it is a case of “circular cause-and-effect.” How is it possible for each element of the interaction to sustain and reinforce all of the others? And what causes this mutual, reciprocal, dynamic interaction? McLean’s answer: Newton’s second law of motion.
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So the recipe might be - one drop of Bernoulli, plus Newton second and third laws ?
 

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