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.
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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 :) ?
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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 ?
 
A simple way to feel lift is to stick your hand out the window of a car with your hand palm down and twist your hand from parallel to the road to positive angle of attack and you will feel the increase in lift or pressure as you increase the positive angle of your hand. Tilt your hand to negative and you will feel it pushed down.

You can do the same with a rectangular cross section strip of wood, which shows that an airfoil is not absolutely necessary for positive angle of attack to generate lift. The airfoil generates lift more efficiently because it smoothly deflects the air around it.

Anything can fly with enough airflow and positive angle of attack.
 
Concerning the De Havilland TK.5 canard that couldn't fly: I think they didn't try enough experimentation to get it off the ground. Just having the landing gear in the wrong place or at the right heights is enough to make a tricycle gear airplane impossible to take off. The other issue that might have made them risk adverse was that the test pilot could be hurt if something went wrong.

Unconventional aircraft configurations are not inherently dangerous or guaranteed to fail. The problems encountered with unconventional configurations is that the solutions to their issues may also be unconventional and require learning new ways to tame them. To reduce the consequences of unconventional aircraft handling, take the pilot out of the airplane and test and refine with models.

It's possible to get almost anything to fly as a model. If the model crashes, no one dies, and you fix the model or build a new one and keep testing. Once the bugs are worked out through getting the model to fly reliably and as much risk as is feasible has been refined out of the configuration, then put the test pilot back in the airplane.
 
Er, planes fly because they have engines. Gliders have beautiful wings, but gliders don't fly, in still air they head in only one direction, down. They can generate lift from residual force of their forward motion generated by a dive but once that is gone, no more flying. For another example, consider a kite. As long as you hold the string you're using the force of the wind to generate lift. As soon as you let go of the string, the kite plunges straight down.
 
Richard N said:
Anything can fly with enough airflow and positive angle of attack.
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I love telling this to people who have minor knowledge in aerodynamics. I’ve always felt that wings really are just a combination of Bernoulli and Newton principles that like what was stated earlier, work in a cooperative fashion. I’d be more interested in the why does the upper airflow go faster, and if it’s a half Venturi/nozzle compression effect…..
 
NUSNA_Moebius said:
I love telling this to people who have minor knowledge in aerodynamics. I’ve always felt that wings really are just a combination of Bernoulli and Newton principles that like what was stated earlier, work in a cooperative fashion. I’d be more interested in the why does the upper airflow go faster, and if it’s a half Venturi/nozzle compression effect…..
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Coanda
View: https://www.youtube.com/watch?v=lYlZ0W3auhQ


View: https://www.youtube.com/watch?v=6Q8HssqWDDE


View: https://www.youtube.com/watch?v=ZmvgMbxmizY


https://www.jafmonline.net/article_2175_d313d41a97d43e7dd1cc201a23cf2a11.pdf

https://www.thermofluids.co.uk/effect.php

View: https://www.youtube.com/watch?v=OCh4svEfDmE


https://mentourpilot.com/what-is-the-coanda-effect-and-why-does-it-matter/

https://en.wikipedia.org/wiki/Coandă_effect

https://www.researchgate.net/figure...ke-conventional-airfoils-the-CC_fig5_27523230

https://www.researchgate.net/figure...tent-for-a-propelling-device-7_fig2_296443394

https://www.researchgate.net/figure...ent-aux-propulseurs-Coanda-1-2_fig3_344321124
 
NUSNA_Moebius said:
I love telling this to people who have minor knowledge in aerodynamics. I’ve always felt that wings really are just a combination of Bernoulli and Newton principles that like what was stated earlier, work in a cooperative fashion. I’d be more interested in the why does the upper airflow go faster, and if it’s a half Venturi/nozzle compression effect…..
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Yes.
A flat plate (see paper airplane) can fly quite nicely at shallow angles of attack. All the fancy curves are just to make it thick enough for structure and to delay stall. The structure is merely a teardrop.
Flat plates tend to stall abruptly.
OTOH Plates with large nose radii stall in a docile manner.
Try to think of the cures on the top of a wing as logarithmic curves intended to match the rate at which it can change the airflow. An airfoil can force a sharp change in airflow near the front, but that ability rapidly diminishes as it flows farther aft and the boundary layer gets thicker.
 
Someday physics will catch up to the fact that helicopters shouldn't be able to fly and any airborne at that moment will immediately fall to the ground.
 
Kanga said:
Er, planes fly because they have engines. Gliders have beautiful wings, but gliders don't fly, in still air they head in only one direction, down. They can generate lift from residual force of their forward motion generated by a dive but once that is gone, no more flying. For another example, consider a kite. As long as you hold the string you're using the force of the wind to generate lift. As soon as you let go of the string, the kite plunges straight down.
Click to expand...
 

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