A New Theory of Lift
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- Опубліковано 6 вер 2024
- In this paper we revive a special, less-common, variational principle in analytical mechanics (Hertz’ principle of least curvature) to develop a novel variational analogue of Euler's equations for the dynamics of an ideal fluid. The new variational formulation is fundamentally different from those formulations based on Hamilton's principle of least action. Using this new variational formulation, we generalize the century-old problem of the flow over a two-dimensional body; we developed a variational closure condition that is, unlike the Kutta condition, derived from first principles. The developed variational principle reduces to the classical Kutta-Zhukovsky condition in the special case of a sharp-edged airfoil, which challenges the accepted wisdom about the Kutta condition being a manifestation of viscous effects. Rather, we found that it represents conservation of momentum. Moreover, the developed variational principle provides, for the first time, a theoretical model for lift over smooth shapes without sharp edges where the Kutta condition is not applicable. We discuss how this fundamental divergence from current theory can explain discrepancies in computational studies and experiments with superfluids.
I'm very pleased that the curvature argument is coming to the fore. I investigated this years ago when I did aerodynamics, but I couldn't quite get beyond replacing the Bernoulli equations with curved flow to calculate lift. Very impressive, Prof. Taha and Mr. Gonzalez
My first experience with "The Unexplainable" was the Flit Gun! I could see it worked, but wasn't content until I understood what forces pulled the DDT up the tube into the air flow! Least Curvature is what birds use for economy of flight. Least effort saves fuel! Proud of your curiosity!!! Be excellent my new friend!
It's obvious that forcing an airmass to follow a curve in one direction (down) will produce an equal and opposite reactive force in the other direction (up). The question is how is the deflection obtained. There are two things at play here. One is a pressure imbalance and the other is the behavior of the airflow. Traditionally people have attributed the pressure imbalance to the acceleration of the airflow over the top of the wing. This is backwards. In nature you need potential energy first before you get kinetic energy. I like to describe an airplane wing as a "wing piston". As the wing piston moves through the air the air is compressed at the front leading edge and rarified from the topmost point on the wing to the trailing edge. As such the wing has a front part and a rear part divided by the topmost point on the wing. As such an initial pressure differential is created between the front and rear potions of the wing, similar to how moving a piston in a cylinder produces a pressure differential between the front and rear of the piston. It is this initial pressure differential that pumps the air over the top of the wing causing the air to be accelerated. When this happens Bernoulli's principal takes over. The acceleration of the air lowers the pressure on the top rear portion of the wing even further. Once this region of low pressure is established on the top rear part of the wing any air molecule that encounters it will be deflected downward along the curvature of the wing. Then the action/reaction principle takes over and the force created by the downward deflection of the air molecule is vacuum coupled to the top surface of the wing, which produces the upward lift. If you think of it this way its not as confusing and it is not that difficult to understand.
WoW, I love that final quote, "The treasures of the world of fluids will not disappoint the persistent explorer". Methinks that this is true of many fields.
Neh! Whisky, man. Whysky. Answeres all! 😁🤪🤪
"So, his work is constantly evolving?"
"Yeah. You could say his solutions are... fluid."
oof
Lift is provided by adding pointless music to everything.
Quite agree this is obviously one of those pseudoscientific videos with outdated information, and lacking any value whatsoever. Mind you they do get a few clicks and make some money hooray for them. What a load of crap.
This needs to be said. Underscore abuse is the hallmark of amateurism. Why do people fail to understand this? Dialogue OR music, never both.
To be fair most people simply don’t have an attention span :/
@@ilricettario hold up, what do you mean by this?
Intuitively this makes sense to me, because a non-Kutta flow would have a region of infinite curvature, and it would be very hard to obtain a minimum under those circumstances
Bravo! Congrats for the breakthrough. A very secondary note for correctness, the principle of least action should rather be called the principle of stationary action as it only requires the first variation to vanish, but not necessarily higher order variations of the action. So nature is not necessarily minimizing the action, it just finds the trajectory that renders the action stationary.
That's an excellent evaluation.
Interestingly, unlike the principle of "least action" where the action is only stationary, Gauss' principle of least constraint asserts that the constraint (or curvature in our case) is really a minimum, not only stationary.
who calls Lagrangian Mechanics Variational mechanics
@@haithemetaha9194 Thank you. I am just a little surprised that reaching your results was possible only using Gauss' principle but not other equivalent formulations of classical mechanics like d'Alembert principle or the principle of stationary action. Shouldn't your result be equally derivable from all other equivalent formulations of classical mechanics?
@@gytoser801 Many classical textbooks of analytical mechanics do :D.
In my opinion, variational mechanics is more general than Lagrangian. However, perhaps the association comes form the fact that variational principles need calculus of variations where Euler and Lagrange played an essential role and the integrand of the cost functional is typically called "Lagrangian".
Doing Aero for over a decade, this is something that never made sense to me. We do so much work without knowing the fundamental principles.
that's actually the reason why I left the aero field for the thermodynamics field during my study career.
There is something here that is deeply reminiscent of the way the principle of least (stationary) action connects to Feynman's path integral!
Birds everywhere can finally stop being so afraid to fly, knowing that we figured out that it really does work.
Airplane wings produce lift using the same action/reaction principal that a rocket engine uses to lift a rocket off the launch pad. The pressure created inside the rocket engine's thrust chamber accelerates the combustion gas downward through the nozzle, which produces the upward lifting force. Similarly airplane wings accelerate air downward to produce an upward lifting force. But how does the wing accelerate the air downward? Basically, the forward motion of the airplane compresses the air at the leading edge causing the air to be accelerated up and over the top of the wing. This creates a region of low pressure over the upper curved portion of the wing. When an air molecule traveling in a straight line encounters the region of low pressure it gets deflected downward as it follows the curved surface of the wing. It's this downward deflection of the air that produces the lift.
How comforting! Now I can go back to Cats that look like Hitler videos!!!
@@patrickjamesdavidarmstrong7271 I love cats videos. Also the Hitler parodies.
Plus the downward deflection caused by the underside of the wing.
@@DavidOfWhitehills That's correct sometimes. With positive AOA the air flowing under the wing will be compressed and deflected downward, which produces increased upward lift. But at zero AOA the air flowing under an asymmetrical wing (with a flat bottom) remains unobstructed so it stays at static pressure, which is the local ambient pressure. So at zero AOA all of the lift is produced on the top side of the wing.
@@joevignolor4u949 Don't think planes fly with zero AOA.
Now compare this to luggage mechanics where a bag will take the longest route to get from LA to Chicago
This is a worthy PhD result. Curvature which lurks everywhere in functional analysis, GR etc etc now gets a seat in business class! I'll look into the relevant paper as this is an important perspective.
This is a great advance, that will hopefully have important consequences in the physics of fluids in general and physics at large. I look forward to more discoveries.
I wish the video creator would LISTEN to their video before posting it
FYI - I couldn't understand MOST of the voices due to the volume of the music AND the type (the chimes kept me from trying to mentally fill in the gaps in the words.
So I'm downchecking this video.
These are engineering-minded individuals grappling, intelligently, with the limitations of the Navier-Stokes equation (or with the simpler Euler version of them which forgets about viscosity). That's fine, but the truth is that the Navier-Stokes equation is an approximation that works when the length scales (e.g. the width of the wing would establish a length scale) are much larger than the average distance between molecules of air. No paradoxes would arise if the problem were to be formulated at the molecular level. It's just that approximations are needed to estimate the lift.
So this would cover being able to explain and calculate the lift from a rotating cylinder or sphere?
The music is tooooo loud !
I really wanted to concentrate on what these researchers were saying but was constantly distracted by the background music. I don't understand why UA-cam creators seem compelled to add music to everything.
As is often the case I cannot hear what the man is saying because the music is too loud why do people do this
There is a Big Difference between the Wing Lift of a slow flying Bird and fast flying Jet ... So what these people are saying , is so well explained ... I don't have a Clue what they are Talking about ? ... D-
It's as simple as F=mA. The entire aircraft is a 'black box', with airflow coming in (reference frame=aircraft) the front. Some of that mass (m) of moving air is accelerated (A) downward, generating an equal and opposite reaction force (F) called "Lift".
Too many theories failing to explain aircraft that choose to fly upside-down, or flat or random objects being blown up into the sky by strong winds. But F=mA works universally.
You'll ask, "But what about what's inside your black box? We're very interested in the wing itself."
Well, there are presently some optimized wing shapes (many, choose your options) to maximize Lift and minimize Drag under some selected conditions, but I don't believe that there's any theorem to prove that there's not another even better design yet to be discovered. So it's all merely 'stamp collecting', but admittedly, very important stamp collecting. If a complete theory was at hand, then the entire topic would be marked as 'complete'. It's not, and isn't. So carry on.
"failing to explain aircraft that choose to fly upside-down" ... please, not that old chestnut ! inverted airfoils use a higher angle of attack.
I remember calculating fluid rotation around an airfoil back in university, a lifetime ago.
The poor audio combined with the several accents overwhelmed by the background ( or is it foreground?) music makes this video very difficult to follow.
So put this in language that a student pilot that may have had some math anxiety in high school, will understand please.
But doesn't this only refine the concept of fluid dynamics related to an airfoil design calculating a difference between the flow above and under the airfoil?
Does this not still not account for any possible Newtonian physics related to actual upward pressure on the underside of the airfoil?
I'm still waiting for a unified theory, unless it's just too simple to manually combine both theories.
Thinking about this refinement introducing the concept of least curvature, I'm thinking that it would probably assume ideal boundary layer flow and no disruptions/vortices/separation.
I would submit that the least curvature is surrogate for least drag. The shape of the wing is all about minimizing drag. You might get some lift from the curvature, but lift derives mostly from the angle of attack.
And I don’t get how this insight explains why thicker shaped airfoils are needed at slow speed, whereas minimizing drag does.
Here is the (corrected!) citation for the paper: Gonzalez, C., & Taha, H. (2022). A variational theory of lift. Journal of Fluid Mechanics, 941, A58. doi:10.1017/jfm.2022.348
This seems to imply that superfluids CAN generate lift . However , just because they pose no friction or viscosity , doesn't mean they just magically move out of your way when you push through them . Especially at an angle .
Yeah, because superfluids have mass, therefore momentum and inertia.
It seems obvious that air molecules search for a steady state of least energy levels. So, molecules might try to have the largest distance between them to minimize the repulsion forces.
Now we come to a point which often puzzles me while listening to aerodynamics: they often talk about the "flow" of air over the wing, meanwhile they seem to forget that the only moving object is in fact the wing, NOT THE AIR. As such, air does not "flow" over the wing, but simply tries to avoid it. And it will just avoid it as much as needed, before regaining the initial steady state.
We can consider the wing as our frame of reference and as such it's static while air moves. Which is why we can have static wings in wind tunnels to study them. In the real world, we have both the air and the wing moving. Which is why you can take off with less runway when you have headwind.
Not sure how the air "avoiding" the wing would create lift. I see it as quite the opposite. The air molecules displaced by the wing pile up and naturally exert a pressure on the wing surface. The unbalanced pressure above/below the airfoil generate a net lift due to the assymetrical surface areas.. So, the air isn't avoiding the wing, it's pushing back. The flow dynamics are a different story generated by both the pressure gradients and drag forces. But, I'm no FD scientist!
Why drown out people speaking with loud music?
Extremely interesting but, SO hard to watch. Between the bad recordings of the speakers (too much room ambience and very bad EQ) and the music (loud, soft, loud, soft).....geesh! Exhausting. For starters, you might get rid of the music.
I watched/listened on my back porch. While watching, a nearby car alarm went off _and improved the experience_! (True story; no kidding.)
@@utoddl lol
Because it's done by amateurs. But the content is very interesting
I've wondered about boats floating in water and their displacement of water and how a flying plane compares to that. It (the plane) must also displace something. Of course it must be the atmosphere that "floats" the plane, but what is the distribution? A massive plane can fly low and directly over you, but you don't feel crushed. No matter where you or a million other people under the plane stand, nobody feels the weight of the plane pressing down on them. So how large of an area of the atmosphere does bear the weight of the plane? What is the distribution?
Imagine if you were in the water, would you feel the weight of a boat above you? In the boat analogy it becomes more clear if you think about being in a pool. If I put a boat in a pool the water is lifted slightly and offsets the weight of the boat. Its like the surface of the water is some crazy 3d fulcrum. As soon as enough water is displaced to equal the weight of the boat it stops sinking. If you expand the pool outward to a bigger and bigger body of water the amount of water displaced remains the same but the change in height approaches zero. A plane works differently, its not floating due to displacement. It floats due to lesser understood fluid dynamics. To me the plane flies because the vortex created above the wing and the vortex's being shed down the side of the fuselage are lifting the plane into that low pressure zone. If you even seen like a Styrofoam cup or piece of paper float in the air behind a moving truck, that's what I'm imagining. It does make for an interesting idea though, even if the plane is being pulled upward into a low pressure zone, what's holding it up? You should check out the episode of the mythbusters where the weigh a box truck with pigeons flying inside of it lol
أنا فخور بك جدا
it's starting..this is the beginning of making aircraft like the tic tac ufo now we need someone to figure out how to move OUTSIDE of space-time
Love it. Science at its best. Good job!
Without the clickbait title, and regarding to fear of flying, also without (2:37) saying that some quantity ia magic, it would be grate, informative science video on the level of graduate student of physics. But now it's this wierd mix of true information and emotional manipulation - i think I like it ;D
The emotional manipulation is necessary because the viewers are humans. Not physicists.
Hi. I feel the same way. is there access to the paper?
but it is not just one force or act. There is already pressure dirrerence and there is air resistance. There may also be electrostatic and other factors. Wind speed, direction of travel around the globe?
Instead of the Kutta-Joukowski condition we could impose a condition of zero total vorticity in the flow, which will then give us a realistic unique solution if an aerofoil is started from rest. All the vorticity in the flow in concentrated on the surface of the aerofoil, and viscosity means that it will diffuse outwards. Initially the flow around the trailing edge needs to double back around it, and this fails to happen for a boundary layer containing vorticity. Net vorticity is left behind the aerofoil, and by the topological principle of the conservation of vorticity, there is then bound vorticity associated with the aerofoil, which generates lift.
If the aerofoil has a less than perfect trailing edge, this process can still happen, but flow separations from both the top and bottom of the aerofoil interact to produce a little Von Karman vortex street, which is now an unsteady flow. If the aerofoil mutates into a circular cylinder, then it is pure vortex street and no lift if the cylinder is not rotating.
As one other commentator suggests, let's try dragging a hydrofoil through liquid helium to see what happens.
Kelvin's conservation of circulation cannot be sufficient to determine lift. It simply says that the sum of vorticity in the wake is equal to the circulation over the airfoil. But how much is that? It does not tell. And the entire Euler's PDE cannot tell because it is non-unique. There is a real need for a closure condition (Kutta-like condition), which is provided here by a minimum-curvature argument.
@@haithemetaha9194 Maybe a minimum curvature argument has some validity since a boundary layer can have issues with going round a corner. The video implies that Kutta plucked his condition out of thin air when in fact it could have been deduced from wind tunnel studies and streamline tracing, which is something I have actually done myself, and in addition I have compared experimental results with streamline tracing obtained from the use of the Martensen Method on a computer. It could also be guessed from observations of the starting vortex left behind by an inclined hydrofoil in a fluid covered with iron filings. In three dimensions, the bound vorticity associated with the aerofoil is continued as trailing vorticity from the wingtips which are visible centres of condensation at high altitude.
The video implies that in a superfluid a transverse force can be generated just the same. Is there an experimental prediction being made here?
One alternative to a Kutta condition is full scale computer simulation starting with an initial condition of zero total circulation. I have done that using Alexandre Chorin's method combined with the Martensen Method when I did a PhD. My supervisor was Professor Lewis at Newcastle University. Surely both Chorin and Lewis turned up in the literature search done by the authors of this video.
@@david_porthouse Hi David. First, as you yourself said the Kutta condition could be "guessed". Yes, indeed, this is what the video implied too: the Kutta condition is not derived from first principles, but guessed. And of course it was a correct guess that enabled aviation. The new theory does not contradict Kutta but generalizes it; the video says: "The new theory is more complete than the Kutta condition".
As for the lift on superfluid, the video said that this question is "reopened", so it needs investigation after "physicists thought to have settled". In addition, there is a recent (2019) PRL paper where the authors performed quantum simulations for the flow of a superfluid over a Zhukovsky airfoil and found a quantized version of Kutta's lift.
journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.154502
As for the full computer simulation by the great Chorin and Lewis, it is not very relevant to the story in the video, which is concerned with theoretical developments, not simulations. The video is for a broad audience, and a comprehensive literature survey for a 100-years old field in a 6-mins video is far from being the goal.
Thanks for your comments and interactions.
The video is lacking in the finer details of the theory and there are no links to the aforementioned paper(s)...
The Space Shuttle was considered a Lifting Body... majority of lift not done by small outboard 'wings' but air molecules striking bottom of craft. It was for all intents and purposes a flying brick that barely came home at end of every mission. Totally unpowered flight on excessive glide slope, 1 chance to get it right. No parking Shuttle if it came up short, or went long.
Heard pigs can fly too if given enough thrust.
So you are saying if you run an airfoil through superfluid helium is WILL generate lift?
You've beaten me to it with that question! Yes, let's do the experiments and see what happens.
Congratulations guys, very interesting finding!
In theoretical equations we are assuming that the wing has a perfectly smooth surface, which in reality it doesn't. For a molecule it is a mountainous region, causing micro-vibrations/energy frequencies in all directions. Hasn't it been experimentally established that sound/vibration can also cause levitation (Hutchinson's research) as a form of anti-gravity lift? Has this been taken into account in conventional aerodynamics?
If true, the effect would be equal above and below the wing, thus cancelling out.
Years ago I had a roommate that worked on wind turbines. He said air just doesn't want to play nice with the blades - something to the effect that it does everything possible to not try to push the blades (I might be really munching up his words / ideas here because he told me this in the late 90s). I wonder if this new understanding can help with wind turbine tech as well?
Beautiful result.
Excellent but where is it published?
I wonder if you can also use a Feynman path integral solution logic, but then with all the Euler solutions and whether it gets the same result as the least curvature solution. Just out of curiosity
If I understand correctly, Feynman's path integral relies on the principle of least action. Interestingly, when we minimize the action (kinetic energy), we get ZERO lift. Very interesting!
@@haithemetaha9194 I think the result of the path integral is least action, but it actually consists of the integral of all possible paths to explain that least action. Correct me if I'm wrong
I wonder what the result would be if you made an integral of all the Euler solutions for lift, what would it look like and would it also produce lift?
@@Robinson8491
I think this sum (integral) of all the possible solutions in Feynman's formulation is because of the stochastic nature in quantum mechanics, not sure though. The problem here is deterministic. So, the classical action principle (without Feynman's extension) should directly apply, but it, interestingly, yields a zero lift force as I mentioned.
@@haithemetaha9194 okay, then I'd like to formulate it differently: could you use a Feynman diagram kind of logic, as in sum every allowed solution to find the actual solution? Considering there is a limited amount of solutions, and it is probably asymmetrical, this is likely not identical to the least action
Just being very speculative here, thinking out loud out of curiosity
Something in quantum mechanics is random, which we can represent in fluid mechanics by the Brownian motion of vorticity, the latter idea being due to Alexandre Chorin. Any path integral formulation would integrate the randomness out of existence. The aeroplane would then be attempting to fly through a superfluid, which is not possible.
Aerodynamics is always discussed in terms of air flow, but it bears considering that air is basically not moving until an airfoil comes along, moving through it at high speed. Whatever the mechanisms involved, the net result is that air gets pushed downward. Air molecules have inertia, so pushing them down results in an upward reaction force. This is obvious in the case of a helicopter, which creates a strong downwash of air.
air is absolutely CONSTANTLY in motion.
that is what temperature is, after all. the average kinetic energy of all particles in a medium
Great. I was beginning to think that I was the only person in this entire discussion thread who understands all this. Its good to know that I'm not alone. Thanks.
I always thought planes flew by magic...
Do you have a very dumbed down version of this video for pilots?
My model aero plain I built as a boy in the 1960's with a main wing consisting of a symmetrical sheet of thin Balsa wood flew perfectly well and that without control of it's motional pitch against wing air flow since I had no radio remote control.
Later, explanations of lift produced by upper wing curvature never made much sense to me.
Such curvature may well assist lift but it seems not essential for flight, provided the motional pitch against airflow can be adjusted.
Can someone please explain why symmetrical wings fly at all and bring me up to a more scientific state of knowlege?
@Grim FPV Explained well in simple terms and what I thought all along. Why else would an air craft need to rotate at a certain speed to take off. Thanks and cheers!
@grimfpv292 I think the thickness of the wing is not only about packing in enough structure. It’s also about drag. For a slow aircraft to need a larger wing to deflect the air. However, with a thin wings, very small increases in angle of attack cause a disproportionately greater increases in drag. The laminar flow over the wing is quickly disrupted causing a vacuum/void/low pressure zone above/behind the wing. If you have a thicker front of the wing, you can manage high angles of attack (and hence higher lift) before drag over takes available thrust.
Music waa VERY distracting.
Roughly speaking as a science interested sub-engineer, also speaking because lots of people discuss in this topic.. i think a lot of power that keeps plane on air is due to the momentum it has. Remaining comparitively small portion of force supporting lift and motion is only provided by engine and aerodynamics
Where Eagles Dare. A new theory, but an old wing.
Nice, but why add music to this?
What keeps planes in the air? One word: MONEY. ;)
I'd love to know more about this.
Here is a good place to start: www3.eng.cam.ac.uk/outreach/Project-resources/Wind-turbine/howwingswork.pdf
Think watching slow motion videos of a bullet going through gel can help explain what I think is going on.
As the bullet travels through the gel it gives the gel inertia as it pushes it out of it's way. As the bullet travels past, the inertia in the gel continues to carry it away and creates a vacuum behind it.
A wing is doing the same thing, the gel is air and it tries to favor one side.
It isn't hard.
The pressure on the top of the wing is lower than the pressure on the bottom of the wing.
QED.
So, can we now expect new foil shapes in the wings of planes?
No that won't be happening anytime soon. We have near exhausted the effects of aero foil shapes and their efficiency or lack of. since none of this video is actually disproving lift or aero shape.
@@kiwidiesel I was hoping for new shapes with new aerodynamic properties. It is known the the foils of mono-wings must be somewhat different from the foils of ordinary planes. Can we expect foils in the future with some unique properties?
So...what happens if you reverse the airfoil shape and put the bigger bump on the bottom rather than on the top of the wing? What is the result, and why?
Keep in mind that airplanes can fly inverted.
Then it becomes an F1 car.
Are you saying that you derive an equation for the radius of curvature and find the minimum of that distance? I think that's right. Thank you.
Power= Speed and Aerodynamics= airfoil = lift all are required to keep an Aircraft flying!
Could the principle of least curvature have some relationship to a liquid taking on the shape of the container that contains it?
I think in that situation it's easier to think about potential energy: the liquid takes the shape that minimizes its total potential energy, constrained by the container.
Planes are actually kept aloft by thousands of bumble bees hidden in the wings.
The acoustics and sound on this video are terrible. I had to rerun multiple times with text to understand what was being said.
I can't tell what you are talking about. Must you play that darned music?
Go Cody!!!
That music is annoying and sooo distracting. Much better video without it. However, thank you for sharing these revelations on lift.
Is this another application of δS=0 ?
Thank God I hardly understand it glad I'm not the only one.
So, could this theory be used to design better, more efficient, wings?
Quicker designs I'd imagine.
What generates lift? It's simple. Santa takes things up in the air.
Perhaps someone more knowledgable can answer this question: isn't lift essentially creating a slight vacuum above the wing, perhaps at least in comparison with the pressure underneath it?
Let’s say Yes for the sake of argument. Now do the math to calculate exactly how much lift a given wing shape will generate at a certain wind speed and you may begin to see the point of this video.
@@anatomicallymodernhuman5175 Wouldn't the answer be either "yes" or "no?" If yes, then the vacuum can be calculated and consequently the amount of lift determined as the vacuum is applied to the upper wing surface and the host of other factors that go into that. I have no doubt the formulas are not explained as a vacuum because "lift" is the calculation combining that variety of factors, but the actual force involved is vacuum, as it seems to me.
@@grandrapids57, Work it out mathematically from first principles. It seems that a lot of commenters here are missing the point of the video. It's not about the practical aspects. It's about fully understanding the fundamental physical forces involved.
that's what i thought. but, i have realized that the pressure zones above and below a wing are a result of a wing that has positive aoa, moving through air. there, thus, is a simple newtonian explanation of lift from positive aoa.
as it moves through the air, a wing that has some positive aoa pushes down on the air, and the air pushes back. voila, LIFT.
(it can be seen that bernoulli-based calcs and/or simulations that simulate Moving AIR are less-than ideal.)
it is informative to consider what happens when a flat plate profile/airfoil that has some positive aoa moves through air. there will be huge amounts for turbulence/reduced pressure/DRAG at the upper surface of the wing; over its entire chord/area.
this is why the upper surface of a modern, efficient profile is shaped the way it is. so that, the profile/airfoil occupies the space that would otherwise be full of Turbulence/drag.
because the 'moving air' model is flawed, it can be seen that a typical streamline illustration is more confusing than informative. cheers
This sounds like the Principle of Least Action.
Venturi effect ?
It would be a great first step if people would stop repeating the nonsense theory about faster airflow over the top creating low pressure. Wings create lift by deflecting the airflow downwards thus creating a reaction that pushes them up.
why is this so hard for people?
@@brettharman8921 because its not correct, lift isnt ONLY generated by reaction force. In fact, more lift is generated by air over the top of the wing than the bottom. An airfoil is more efficient than just a flat plate at an angle because reaction force isnt the only thing at play
@@nade5557 i agree that lift is also generated thru negative forces over the wing. i do not agree that the negative forces are greater than the positive forces below.
@@brettharman8921 you can disagree sure, you'd just be wrong. People have measured this, unless the flow is supersonic the top surface generates more lift
@@nade5557 i go by MIT aerodynamics-
interesting, but it doesn't explain the lift of a flat plate, where there is curvature at the both ends... neither the sails
A flat plate edge-on to the relative wind will not produce lift. But tilt it upwards and it will. It has nothing to do with curvature but with the fact that the leading edge forces air upwards against the undisturbed wind, where it is slightly compressed. This makes the disturbed air flow faster and that pulls some of the air above the plate with it, creating a partial vacuum. The difference between the air pressure on the bottom of the plate and that on the top produces lift.
@@paulmartos7730 the video here speak about the fact that you can replace in some cases the kutta-jowkowski condition by a condition of curvature minimisation in the flow. For a flat plate with angle of attack, the curvature in the flow is symetric in the both end, and then this theory seems not adapted for a flat plate. With a kutta-Jowkowski condition on the trailing edge side, you can predict lift at small angles of attack.
@@paulmartos7730 angular tilt from a relatively horizontal position intrinsically introduces curvature, does it not?
Lift can be obtained from a flat plate, but there will be a flow separation at the leading edge which will result in a very turbulent boundary layer on the upper surface. Try a simple aerofoil like NACA0012 instead.
@@paulmartos7730 This is absolutely correct. Difference in air pressure between top and bottom of wing produces lift. There's no question about it.
But the air isn't flowing. It's the wing that is moving.
they both have the same effect
@@nade5557 yes. but. the air particles aren't "deviating from a straight line" as per Hertz. It's not "curvature". The wing pushes them aside (up or down) as it passes, dragging them along it's axis of movement due to friction, coanda as it does.
Nature might be minimalizing that vertical movement, which would look like minimalizing curvature, but by saying the air is flowing, it's introducing a new (horizontal) axis into the equation.
It comes down to where you attach your viewpoint, or camera. If you're looking at the wing, the air flows. An air particle would move XY and t. But if you're looking at the air, the wing moves. Y and t. Discounting drag/coanda etc.
@@pcread but you still have to consider the wing's x axis movement, because when the air is still and the wing moving the air still moves in the x axis. Looking at the effects on both the wing and the air, they are the same regardless of the viewpoint. You might be onto something though, perhaps the air minimises it's total average movement (temperature added by the wing)
If a 5 year old can not understand what you mean, then you do not know what you mean.
Einstein.
I always thought that the impact of the moving wing's bottom surface with the air particles caused the pressure on the bottom of the wing.
The rest of the wing's shape was just streamlining of the wing's structure.
That's why Angle of Attack is important so stalling does not happen.
A streamlined shape achieves minimum resistance when moving through a fliud in the design orientation.
and that's well known because stunt planes fly upside down without a problem. floats, on float planes are supposedly designed to aid lift but from what i can tell they look like upside down wings.
Any 5 year old should be able to download a computer simulation of the Navier-Stokes equations and run it. I would select Excel VBA as the initial platform, and Alexandre Chorin's approach to the Navier-Stokes equations based upon the Brownian motion of vorticity as the initial model. This can deal with aerofoils. Maybe 5 is a bit young, but I could certainly have done something like this when I was a bit older. I have a spreadsheet available for the motion of an electron in a dipole magnetic field (i.e. the Van Allen belt) which is available now. This isn't science fiction.
@@david_porthouse
I rest my case.
Hahaha Hahaha
I see the wing (and its angle of attack) as casting air down, in other words, creating a vertical component to its motion. After that, it's just F=ma.
@@d.jensen5153 yep
The remainder of the wing shape is streamline for the air flow, with minimal resistance to the forward motion.
I understand less than half of the thing they talked about. But it feel more like a Kickstarter promotional video disguise as argument for a scientific hypothesis.
The audio is terrible!!!
Why can't physicist just simulate this problem based on particle physics? I mean like make a small wing made of atoms literally move through simulated air molecules. Then they don't need to theorize or approximate. I get that this will need insane amounts of computing power but isn't that issue solved nowadays?
Probably because it would be impossibly costly to implement such theory, even as a simulation. Even molecular dynamics (MD) for air particles as spheres would be also impossible. I don't think that a microscopic model would be useful in here. That is why they have to treat the fluid as a (sort of) continuum, obeying the laws of hydrodynamics.
Just to make it clear, the largest MD simulation involves a few billion particles (lets say 10^10 particles). Any realistic enough simulation, capable of truly explaining the Kutta solution, would involve 10^25 or more particles.
Because it is a lot cheaper to simulate it with a model based upon the Brownian motion of vorticity as a representation of the Navier-Stokes equation.
The essence is simple:
*Air* goes *DOWN.*
*Airplane* goes *UP.*
Sir Izzy Fig Newton approves of this one 🙂
Yes it does. Simple, isn't it?
Thanks, now all makes sense-
thats not the full effect. Otherwise a flat plate would make the same lift as an airfoil
@@nade5557 Depends what you mean by "not the full effect." The law of conservation of momentum dictates that 100% of the "full effect" is that the force of acceleration of air downwards exactly equals the force of acceleration of the airplane upwards. The only question is exactly *why* the air is going downwards.
You are not addressing takeoff and landings. The plane is always adjusting its flaps and leading-edge slat. The images you are showing are not what a wing looks like at 36,000 feet. Airplane wings are active and moving parts like the wheel of a car. One rides the air the other the terrible roads on the ground.
Flaps and slats are helpful, but an aeroplane can fly without them. A big aeroplane leaves behind a starting vortex on the runway and it can be dangerous for a small aeroplane to follow it straight away. This video has nothing to say about vorticity.
Aircraft flew before flaps and leading edge slats existed.
@@ChucksSEADnDEAD For the purpose of this discussion think in terms of aerofoil section NACA0012, which is a thin symmetric aerofoil with no slats or flaps. An aeroplane which uses NACA0012 is able to fly, and can fly just as well upside down. This new theory of lift is apparently saying it can fly even if the atmosphere were a superfluid. I don't agree.
Lift is the result of thoughts and prayers.
subbed.
Not a new theory of lift at all, just a new way to compute lift? And let’s be honest…we’re very capable of approximating lift very, very accurately now.
Why is this utterly irritating "music" necessary?
Nature do not have any desires. Explaining that nature wants something is childish at best.
Interesting content spoiled by terrible sound quality and an unnecessary musical track.
please cut the background music. super irritating
If there ever was a need for subtitles, this is it. The man hammering away on the xylophone made it impossible to hear, and what one could hear, was lost through poor recording and muttering accents of the speakers.
They and talk about all of the calculations and sharp edges all they want but anyone that has ever owned an airplane can tell you what makes airplanes fly
IS MONEY and it takes a SHIT LOAD OF MONEY.
This is why we do flight testing.
Is minimum curvature the same as path of least resistance?
How do you define "resistance"? If you mean least energy, then the answer is no. Interestingly, the path of least energy expenditures results in ZERO lift.
@@haithemetaha9194 Do you mean least energy dissipation? I have seen the principle of least dissipation applied to the understanding of dense granular systems under shear. They yield nice results when one looks for the formation of shear bands (see Unger et al, doi:10.1103/PhysRevLett.92.214301).
It is a completely different physics, of course, where dissipation is of utmost importance.
@@haithemetaha9194 I suppose I mean path of maximum efficiency.
@@wellesmorgado4797 Oh, I see what you are saying. This theory, similar to the classical theory of lift, assumes an ideal fluid. So, there is no dissipation.
Minimum dissipation represents the governing physics in Stokes' flow (i.e., in the limit to zero Reynolds number). The lift problem lies in the other end of the spectrum: in the limit to an infinite Reynolds number, where dissipation may be negligible with respect to inertial forces.
You have not mentioned the Coanda effect.
Because it's irrelevant. Air flow over the top of the lift generating device is not in a condition to provide lift through Coanda, requiring a powered high pressure air source and ducting it over lift generating surfaces.
Nonsense. Least action is STILL least action
So... did Viktor Schauberger invent a flying saucer after all?
After watching this video, I thought 'Now, mix this with Schauberger'. There might be surprises along the way.
Deceptive wording. To say that nature chooses a path of least curvature is a phrase easily exploitable by those who seek to misunderstand.
Video has mixed production value. My first move would probably be to clean up the audio of the interviewees, rethink the music, and rethink the narration.