Thank you so much (I already own curiosity though, lol)

6:05 I understand your explanation of the what creates the lift force (i.e. a pressure difference due to velocity difference, according to Bernoulli's Principle) but then... 6:30 I don't see why the fluid flow being "pinched" above the leading edge of the wing results in LOWER density/pressure? Instead, I'd expect this constriction of air molecules to cause HIGHER pressure? 6:42 I also don't see the connection with "Conservation of Mass" which you state, but don't explain. 7:08 Again, you state what the flow would look like without circulation but you don't explain why.

Conservation of mass means that for the same amount of fluid to flow through the constricted section, it's velocity must increase. And Bernoulli's equation tells us that an increase in velocity is accompanied by a reduction in pressure (conservation of energy).

@@TheEfficientEngineer Thanks for replying with an explanation, which helped me understand how Conservation of Mass applies. I also watched another video explaining how wings create lift (by the channel Sixty Symbols) which I found helpful. How circulation is relevant in this case remains a mystery...

@@GonzoTehGreat It's best to think of the air as a fluid. Also whatever the reason, it is the difference in pressure between the top and bottom of the wing that does most of the work. The various reasons, Bernoulli, Coanda or Newton, will have varying input depending on speed and angle of attack. Flaps only work at low speeds. At cruising speed they just add drag. Same with angle of attack. It took until computers became powerful enough to do the calculations for some of this to be unravelled, so its no wonder that it is still being argued about! Edited for spelling.

I’m going to shamelessly steal this pun

Just the third one 😄

It also stresses laymen like me. I know that wings create lift. I still don’t understand why, though sometimes I think I do

Nobody understands why. That’s why it’s called the theory of lift. Even super computers only get close to quantifying it. We only know what conditions need to be satisfied to create it, not the why.

@@Bartonovich52 Oh, I am glad to hear that! I thought it might be a shortage of understanding on my part. So, in essence, we have a description or the ‘what’ of this phenomenon, not the ‘how’ or ‘why.’ Thanks

Really? I thought we have proved that the lift is caused by the Coanda effect not the Bernoulli effect.

@@jackz1620 Coanda is just a small part that allows the boundary layer not to detach from the airfoil and produces a bit percentage of the lift with the downwash but lift is based mainly in pressure differencial by bernouilli effect

pitty it is not based on physics for all the benoulli version. See my comments above.

@@jackz1620 ​ @Ignacio Trueba Coanda does not happen above an airfoil. It is a jet or sheet of air, FORCED into an otherwise still air environment. There is continual entrainment. There is neither of those above an airfoil. . Using the "Bernoulli Effect" as commonly done is an equally incorrect way of explaining lift. *Understanding Lift Correctly:* rxesywwbdscllwpn.quora.com/

Totally agree!

Would you comment, or LIKE if appropriate, this short piece of the story for the layman? My 11 yo granddaughter did all the editing. *ukposts.info/have/v-deo/a32EpZilmYF1zoE.html*

It's not totally correct

@@baloog8 yeah, I agree, I started to learn fluid mechanical to understand exactly how this aerodynamics works, because I learned solid mechanical approach, so it's a little different when you can think a solid as fluid with an extremely high viscosity.

Lift is action and reaction. The action is the deflection of air molecules downwards, the reaction is the wing being pushed upwards. Pressure differences are secondary. If there is no downflow of air from the wing, there is no lift. R

Life is not totally correct, but we can enjoy it.@@baloog8

Absolutely insane how I’m in the last 2 weeks of fluid mechanics and we’re doing external flow now, and this guy uploads precisely on lift 😂

be careful, physics and engineering are two different things! Still no one is certain on how an airplane flies!

@@rogerdodger8813 I would say people are certain on how airplanes fly, just lacking in certainty regarding deeper issues relating to CFD.

@@rogerdodger8813 That information has the value of zero.

Glad to hear it - thank you!

Watch large jets taking off or landing in the rain sometime. You can sometimes catch a glimpse that the air and water spray over the top surface is moving substantially faster than the jet is even travelling down the runway, and the air is actually accelerating over the wing, past the flaps and then downward.

The explanation with potential flows (uniform+circulatory) is actually more practical as they are used in many preliminary design tools like xflr,xfoil etc

Yes. The textbooks approach the problem in a piecemeal yet detailed fashion. And in the end, you are either completely confused, or the lightbulb goes off in your head. What is funny about the Kutta condition and Circulation is that you can see these first hand by doing an almost childlike experiment in the bathtub with a model airplane wing , and pepper sprinkled on the surface of the water. In effect a 2D wind tunnel, where you move the wing through it instead of the water moving. The pepper particles show the startup vortex off the trailing edge of the wing (Kutta Condition), and when you move the wing from right to left through the water then suddenly remove it, you see a ghostly slow clockwise motion (Circulation) of the area where you removed the wing. Got this little experiment from a book called Aerodynamics for Engineers. So I guess its college level.😜

good video with wrong explanation

no, it's not.

Thanks. :) Agreed, circulation is often not discussed which is a shame!

hey man, uni student here and im always confused abt what circulation is. yes , there is a mathematical definition abt it but what is the physical meaning on it?

at 3:53, the secret to lift is Persistent zones of PRESSURE difference.!!!. not circulation

@ David Davids Pressure difference would not exist without circulation. A tiny spoiler on top of the wing is very good at stopping circulation and instantly destroying lift.

@ ileonlite Circulation is what you are left with after you subtract the free steam vectors from the airflow around a wing.

no, it's not.

Yes, it is @@SoloRenegade

same here

Lift is action and reaction. The action is the deflection of air molecules downwards, the reaction is the wing being pushed upwards. Pressure differences are secondary. If there is no downflow of air from the wing, there is no lift. R

⁠@@RalphEllisto get to the action ur describing is through out the differential pressure caused by the airfoil. With no action there’s no reaction 3rd newtons law 😂

Keep looking, there are far better and more accurate explanations of lift on UKposts. This video is full of misconceptions and inaccuracies.

there is far better on youtube, and that are actually correct, unlike this video.

And also mentioning Newton's law too. A big plus there

wrong. 1) lift occurs BENEATH a wing. 2) a major Source of lift is the presence of a Persistent Zone of Reduced pressure (eg, a specific pattern of TURBULENCE.) ABOVE a wing. 3) not circulation

@ David davids Wrong. The lower surface of the wing not only has almost nothing to do with lift creation... but there is actually low pressure under most wings. The only wings that create high pressure underneath them are supercritical airfoils which still need the low pressure on the upper surface for a lot of the lift and most lift at higher angles of attack and lift coefficients... and the few fighter aircraft that can do high alpha maneuvers at which point the drag coefficient is about ten times as high as it would be to create the same lift coefficient in at a lower angle of attack. If your theory is true, explain how a tiny spoiler or a layer of hoar frost on top of a wing can be so effective at destroying lift.

@@Bartonovich52 'there is actually low pressure under most wings' ????? jeezuss. that massively incorrect statement tells us all that, we can IGNORE anything else that you might say. out

@@daviddavids2884 I am not sure whether you couldn't comprehend whatever is depicted in the video or just needlessly trying to be a moron by just completely ignoring what is being explained. 1) True , there is lift below the wing.2) True, the cause of the lift is presence of reduced air pressure above the wing.3) But the video addresses why is there such a pressure distribution...that is a level deeper in explaining the cause of lift than what you know or think...that specific pressure distribution is in part attributed to a mathematical equivalency of circulation

no it's not.

Nice! and just to add a little: Higher pitch attitude on landing also increases landing run on nose wheeled aircraft as the maximum application of brakes requires the nose wheel to be on the ground. This nose lowering time is limited by the aircraft structure. Thus in the case of flap failures it is often the case that the use of slats is limited to some intermediate position.

While technically true, it's not uncommon to refer to the "suction side" and the "pressure side" of an airfoil, and it's fine to think of them that way in the context of gauge pressure. Sure, the reality is a reduced inwards pressure, but mathematically and even conceptually, it works just fine either way.

Yes but that is annoying and incompressible flow is so pretty!

No, it would not remain unchanged. With significant flow separation at the trailing edge the Kutta condition no longer holds, which leads to a great reduction (and sometimes even total reduction) in circulation. Circulation is the cause of acceleration on the top surface. Less circulation -> less acceleration -> less reduction in pressure on top (Bernoulli) -> less lift. It is not Newton or Bernoulli, it is both, and by exactly the same amount. They are equivalent. Two sides of the same coin.

Hey nigga

flat piece of plywood produces the same lift when tilted.. so youve proved nothing..sorry..dr johnny

But why does the faster velocity occur? And why is air deflected downwards? A faster velocity on top and slower on bottom is the definition of having circulation

Thank you

The propeller blades are clearly curved as to incline the airflow backwards, the direction the trailling edge is pointing is something a 2 year old would realize so I'm not gonna spare you for that, and they do essentially the same thing, low pressure area in front of the blade. And wingtip vortexes don't travel downwards, wtf, you can see planes flying through smoke, the votexes grow bigger over time, but they stay in the same general area. I am only finding it now that there's the equivalent of Flat-Earthers for fluid dynamics, I thought it was too smart of a field for you guys to bother.

what if both theories are applied at the same time

Bernoulli is just a rewrite/application of Newton. Look at how the Bernoulli principle is derived if you don't believe me.

Finally, someone who knows lift has nothing to do with Bernoulli and everything to do with Newton.

@@P13586 For the life of me I don't see why this is so difficult to understand.

You are talking about the 3rd law by the way. Anyway, you are partially correct, Newton's downwash is one reason, pressure difference is another though. You need both on planes like a 747. But no sane person is arguing about that. The only thing that is hard to explain is why the air travels faster at the top. Everything else is trivial.

Unfortunately, you have been mislead. As I previously posted: . It's rather disappointing to see, while this engineer have good intentions, He uses poor wording in several places. . I see the following problems here. . The graph at the left at 4:14 shows the change from ambient, or gage pressures. Saying that pressure above “is greater”, as you do, is misleading and confusing. . It is more correct to say that the *change or difference from ambient* is larger above. You do refer to it as "suction pressure" which sort of says it, but we must remember that you don't actually suck or pull on a fluid, but suction is an accepted term short for “lowering the pressure so a higher pressure can push toward it." .. Unfortunately, he also repeats the big fallacy at 6:15, that the "increase in air velocity creates an area of lower pressure." This directly violates Newton’s Laws. Acceleration does not cause a force. Force causes acceleration. He also states the equally incorrect converse about the lower air "decrease in velocity creates a higher pressure." It is exactly the opposite. Air has mass and a force is required to accelerate any mass. It is a pressure difference that provides this accelerating force to slow it. . The fact that the velocity increase is accompanied by the pressure decrease (and visa-versa) IS CONSISTENT WITH Bernoulli's Principle. However, Bernoulli's Principle DOES NOT assign a cause and effect! It only says that a pressure changes and velocity changes *accompany each other.* . In the mid 1700s it was Euler, following up on Bernoulli's work, that determined that it is a Pressure Gradient that Accelerates fluid. This is Newton's Laws operating in fluids. When there is a pressure difference between two locations, the higher pressure pushes more and accelerates the fluid toward the lower pressure. This is simple and intuitive IF you understand what Newton was supposed to teach you. . Pressures are the cause! . At least he correctly states that the top/bottom pressure difference _is_ the lift. . Then, using Kutta as the cause is equally poor. It still does not explain what the force is accelerating (or decelerating) the air above (below). Kutta is something that had to be added because the initial mathematical calculations failed to correctly model the actual flow - to correct the math, not to make the flow correct. . The circulation story is also backwards. Yes, we can *deconstruct" the flow into two components; one unidirectional and one circulating. BUT what is it precisely that causes this circulation? This story says it is because the air can't make that turn around the trailing edge, but this still does NOT explain the force causing the accelerations we see. We can directly observe the air NOT curving backwards around the trailing edge. Why would it want to do this swirl-around stunt? . As @icojb25 explains so well in another comment: “In terms of the circulation, I guess one needs to understand "circulation" is actually a mathematical concept (ie not real) - used by physicists and engineers in the 1920's when trying to come up with the first aerodynamic theories (like thin airfoil, LLT etc). So remember, there is no magical vorticity "circulating" around the airfoil generating lift. Its a very elegant concept though, and great for many simpler explanations. One just has to decide if you want to explain a physical phenomenon using a non-physical (abstract) concept like circulation, however elegant.” . The pinching above is not just "incomplete", but completely false idea because there is no wall further above ...AND...AND there is another “Pinch Point" right below the wing (time 6:43), where it is "pinched" from above by the wing bottom BUT with NO speed increase, nor pressure reduction!! In fact, the pressure is higher and flow slower.!.!.!. Therefore, serious problem with "pinching". BAD SCIENCE. . Yes, That "Newton Action / Reaction" thing does occur! It must! However, it is the (net) pressure that pushes up on the wing (AS you correctly state with the pressure difference talk) BUT those VERY SAME pressures also cause ALL accelerations of air around the wing. . Bottom line: Once you understand the most fundamental principle, that cannot be violated that: Pressure Gradients CAUSE Acceleration, then everything is easily explained -- cause and effect included.!. See *Understanding Lift Correctly:*. ***rxesywwbdscllwpn.quora.com/*

@@Observ45er I read your previous post, and have responded directly to it, as it is riddled with errors.

@@XPLAlN I'll stay in the other thread to avoid confusion and have answered there.

Nope it is not. Another non-physical explanation . Nothing said about origin of FORCE. Not Energy conservation and not 3d law of Newton can explain FORCE

@@AndrewPa do you have a link to a description or a description of your own?