Forget Bernoulli and Newton | The easy way to explain lift

[@notjackschannel5380]

It’s such a pleasure to see someone admit that their previous knowledge was incorrect and unabashedly correct themselves when presented with better information. And THAT is what makes you a true scholar. Well done, please keep these videos coming 👍🏼

[@zooknz1711]

Could not agree more. Well done Magnar

[@77thTrombone]

Not necessarily a scholar, but a man of honor. 3 words that are hardest for men to say: -I love you.- I was wrong.

[@timknight5105]

It's refreshing to see someone admit their earlier work was not correct and then come on here to correct. Big respect! And thanks for the clarification!

[@jmevb60]

I really like his boldness to address a well worn subject. His interest in understanding at the expense of ego is very refreshing!

[@josteineide7285]

short add. We must consider what comes first, pressure changes or mass deflection?. Our first action is initiated by moving / displacing the mass package. Than by the inertia, the compressibility and viscosity, i.e. stretching of the rubber band comes the changes in pressure and the adiabatic temperatur changes. A continuous process.

[@petep.2092]

What causes the displacement of the mass package?

[@singh2702]

@@petep.2092 The leading edge of the aerofoil causes greater mass of air to be accelerated upwards , hence causing a compression in that direction which then in turn causes an acceleration in the horizontal direction.

[@Hopeless_and_Forlorn]

Look at the larger picture and lessen the confusion: a heavier than air aircraft can sustain itself in flight ONLY by accelerating a mass of air downward with sufficient force to counter the force of gravity. Regardless of what goes on on the top or bottom of the wing, or on any other aerodynamic surface, the net effect of the interaction must be that air is accelerated downward, or the aircraft will fall toward the ground. Hope this helps.

[@FlywithMagnar]

Yes, that is true, but the acceleration happens over the curved leading edge and upper surface of the wing.

[@grejen711]

@@FlywithMagnar And that affects it's behavior at specific angles of attack and makes it less draggy (more efficient) but it does not change what is happening. Air is shoved up against a surface of an objected being shoved through the air. The object is getting pushed by the air as it moves past. Even if the leading edge and upper surface of a 'wing' is not curved at all it still gets forced around by the air moving past it. If you're careful you can direct that force against gravity and call it lift. The curves just make it easier to control.

[@mountainflyhigh]

@@FlywithMagnar - Almost all of the downward force is produced on the bottom and at the trailing edge of a wing. Just look at any wind-tunnel with smoke video. Equal and opposite reaction of a mass.

[@brlinf06398]

it must have angle of attsck thingy

[@guyglover4883]

Spot on.

[@josteineide7285]

Hei Magnar, Quite an improvement which I can follow nearly to the end. There is still a confusion re Bernoulli's. We must not forget about viscosity, bounder layer, energy, Joule Thomsen, and more Bernoulli's is valid along a single streamline. Many professors over the years have differences in understanding and explanations. The sum of it all is quite up to what I learned taking my engineering degree in 1979. We must integrate the work done (Newton) by deflecting a mass of air, a fluid, The equilibrium sum equals that halves of the lift comes from the upward deflection up front of the wing, the other halve from the deflected air leaving the trailing edge, i.e. the "vast" the energy is picked out, no more to gain from it. The pressure and temperature changes involved in the process can not pr Bernoulli's definition directly be linked to the process. No fluid likes to be disturbed, moving it is a mass that are to be moved and needs energy. The viscosity forces keep the fluid together which also needs energy to overcome. This in total can be linked to Newton. The rest of what happens are in many ways side effects. Stretching and compressing the fluid while we are moving the mass around. Air has mass as everything else trying to move it around, accelerate it demands energy / forces. 1 kg of air or 1 kg of steel is no difference F=m*a. Except viscosity compressibility etc. Air will by this be more "soft" to move around, like suspended by a rubber band, similar as if the 1 kg of steel was suspended by a rubber band. You can not simply always say Ps1+Pd1= Ps2+Pd2. You can have different velocities but the pressure remains the same. As you demonstrate by blowing down your strait henging papir sheet, flowing air at one side, no flow at the other side of the papir sheet. Pretty presise metering instrument are in use which utilize the effect of Bernoulli's. Venturi Orifice plate, V-cone. Static pressure drop while the flow velocity increase. Rule of tumb pressure drop equals the differences i pipe diameters d/D which are named the beta value, +discharge coefficient adjustments. There is no beta value in free space around an airplane it becomes infinite. A curiosity from the old faction explanation of lift and Bernoulli's you can not split a venturi i halve and say you have "the upper surface" of a wing.

[@TylerPaparella]

This comment is a little hard to follow, but I agree with the fact that, "You can have different velocities but the pressure remains the same." There must be a cause-effect relationship between pressure and velocity that is not discussed in this video. I also agree that external flow does not behave like a Venturi. Additionally, the paper experiment involves a jet stream of air, which is not representative of real flow over an airfoil.

[@singh2702]

@@TylerPaparella Yes Benoulli's principles are for fluids flowing in pipes. The leading edge of an aerofoil accelerates a larger mass of air upwards causing compression in the upward direction , this compression will then accelerate the air horizontally causing an initial decrease in static pressure , which will increase as the air flows along the top of the aerofoil . This is how lift is produced roughly by using Benoulli and Newton correctly.

[@michaelhoffmann2891]

I was fortunate to have flight instructors who gave me excellent rules of thumb with a certain amount of humour: "take 2 parts of Bernoulli, 1 part of Newton. Some times it's the other way around" - followed by going inverted in an aerobatics plane. 😆 That has always worked for me. Once I stopped screaming. 🤣 (no, I didn't really scream, I loved it!)

[@77thTrombone]

Lesson: there are times/places for perfectionism, and times/places for pragmatism. Also: Your inner Mikey was screaming with delight, I bet.

[@ronaldgustafson3073]

The diagram at 5:37 illustrates two-dimensional flow (i.e., infinite wingspan or a wing that goes from one wall of the wind tunnel to the other wall - no wing tips). We operate in three-dimensions (with a finite wingspan) which produces wing tip vortices, downwash, and lift (by imparting downward velocity to a large air mass).

[@FlywithMagnar]

A video about 3D lift is in the making.

[@petep.2092]

The explanation that the vortices off the wing tips create the downwash which creates the reaction force called lift… is a plausible but erroneous explanation. If it were true, gliders with very long wingspans would have to produce enormous vortices to deflect the air downwards all along the wingspan.

[@crimony3054]

3:00 you can see in one instance he holds the paper correctly with an airfoil in it to show Bernoulli working. Then he holds the paper with a tension crease in it to show Bernoulli not working. The fact is that if you use a fair test, the paper responds as expected. I've seen this more than once, and I can't decide if those who do it are just ignorant or deceptive.

[@petep.2092]

Tension crease? Have you tried it yourself? What would be a fair test? He was demonstrating that airflow over a curved surface causes a force in the outward direction of the radius of the curve. He didn't really explain why… "there must be a force" is not an explanation. But he DID show that lift is created when the surface is curved. It is validated by the curved upper surfaces of wings, which are curved further to increase the lift. His demonstration serves to counter the explanation that lift is mainly the air hitting the bottom surface that pushes the wing up. If that were true, a wing wouldn't stall at about 20° angle of attack.

[@aardvark2zz]

There are problems with this at 5:00 . The forces at B and C are opposite at the leading and trailing tips due to inverted curvature thus cancelling total lift. At the tips the lift cancels the lift at the center. This can also be seen by the lack of downward airflow on the right outgoing side when compared to the incoming left side. No total downward flow, no total lift !

[@XPLAlN]

The pressure at B is less than at C. That is the point. Pressure above is lower than pressure underneath. They are not equal in magnitude therefore they do not cancel. There is a downwash off the trailing edge. There is an upwash at the leading edge. Therefore, the flow is turned from upward to downward as it passes across the airfoil. The upwash has a positive vertical speed, the downwash has a negative vertical speed. The change in vertical speed times the mass flow rate is the momentum change of the air. The lift is equal and opposite to that by Newton’s 3rd law. The diagram is not a faithful representation of real airflow but it does serve to demonstrate certain key concepts.

[@davetime5234]

Because there is likely so much mass in the momentum of the vertical movement of air (MxV) relative to its vertical velocity, it may be a challenge to depict accurately in an illustration.

[@slevinshafel9395]

1:07 Why this and not this one 1:09 ? The first image dont show the thurst. just the flow of air. the air from above dont give any thrust. Only the air defelcted from under wing give thrust. Why we should take in consideration the air from above? is because the vortice?

[@FlywithMagnar]

It is the air that flows over the wing that contributes to most of the lift. The ratio depends on the angle of attack. That's why the overside of the wing is so smooth. That's why ice and snow is removed from the wings before departure. That's why when the airflow over the wing is distrubed, the wing stalls, and the airplane stops flying. This video might be helpful: kzbin.info/www/bejne/mmXaYnyvaduJg8k

[@crimony3054]

@@FlywithMagnar You can get a brick to fly if you get it moving fast enough. Speed causes the air molecules to hit the underside and bounce off like ping pong balls. That forces the brick up. Wings do generate lift from the top, too. Now someone will say air doesn't work like ping pong balls, but don't tell that to the crew of Space Shuttle Columbia.

[@Pakshya]

Great job explaining lift that too in simple words!! From your previous video I first learned that what I had learned about lift was wrong, and from this video I learned the correct explanation for lift!! 👍

[@davetime5234]

I'm confused. At 3:38 you say "this is called the Coanda effect", talking about the curved paper. But hasn't it been often suggested elsewhere the Coanda effect in "contaminating" the upper flow with an external source of dynamic pressure relative to the bottom pressure's starting conditions, means this cannot explain lift in the situation of a wing where the air split between top and bottom starts off with the same homogenous conditions (same static and dynamic pressure and temperature). Furthermore, you seem to be following Babinsky in saying the Coanda effect needs to be included in the explanation of lift. What am I missing here?: The Coanda effect, due to the mixing in of an external source of dynamic pressure unequally to one side of the wing than the other, is said to not apply to the case of lift on a wing. Yet both you and Babinsky are saying that the Coanda effect is needed to explain lift? Something that doesn't occur in the generation of lift (without a differential external augmenting source), is used to explain lift? And how does this at all replace Bernoulli, in the sense of conservation of energy not needing to be invoked?

[@williamwightman8409]

I was waiting to see F=ma and it finally was presented. Like everywhere else you have to do work on a fluid mass within a period of time and out of that you get a lifting force vector (minus all the losses). Thanks for the nicely done explanation.

[@kfcmcdonalds]

But its wrong ... still atmosphere has no momentum.

[@rv6amark]

Another wonderful video. As I said in my comment to that video, my college professor would be proud of your explanations.

[@DavidTaylor-es1bt]

I like both videos. I had given "lift" some thought before. There are many questions in Physics that can be analysed in multiple ways. For instance, you can't make a paper thin wing. It would have no strength. But the airfoil shape has a cross section known to minimize drag and can be designed to have some strength. You can make it curved and adjust the angle of attack such that it accelerates air with a downward component. F=ma will give a value for lift. If you consider the individual molecules and their average velocity, then when air is moving, molecules will impact preferentially in the direction of flow and simultaneously have less of their velocity perpendicular to their motion. That would be a way to explain what is at the root of Bernouli's principle. And from there, proceed with the rest. So what a lot of Physics amount to is rules that we expect to hold, when applied correctly. And we use them to disprove errors in our understanding and hopefully get clues to better insights.

[@RaviKumar-sn2lx]

I learnt a lot from both the videos. Thank you, Sir.

[@ShadowAlmighty]

I am a little confused. At 5:00, you say that the air is compressed as it moves over the curved surface. But if the air is compressed, doesn’t the pressure increase? So then at position B, the air pressure would be higher than at position A? And then you say that the air under the curve shape expands, resulting in a higher pressure. This doesn’t seem to make sense to me. Can you elaborate?

[@davetime5234]

The compression happens right at the leading edge which creates the force necessary to change direction in surmounting the leading edge. But immediately after arriving at the top front, there is an abrupt drop in pressure horizontally, which accelerates mass horizontally acting to keep up the mass flow thru rate continuity.

[@dazknight9326]

The Bernoulli principle applied to the prop is that the force going on downward side has more speed that the side going up basically, P factor in making the plane want to turn left a little, this down and right thrust is added to the motor. Really a prop provides lift the same way of a wing foil. Easily explained lift is the result of thrust equals Drag, lift equals weight. Speed applied lowers weight value due to less time to react to gravity, and increases lift, air reflected in another direction by a horizontal surface. So airspeed vs the amount of surface defelction, increases lift more and more. Conventional wings of Cessna, Beechcraft, have enough surface, although incrases drag, slower overall cruise, but to me is worth it, compared to more narrow wings needing more speed to stay aloft.

[@larrye2679]

Really enjoyed the video. For us laymen who are not versed in higher mathematics it really helps. Do you also have a video like this that explains the other forces on an airplane such as thrust and drag, etc. Thank you😊

[@grahamj9101]

As I've stated elsewhere, It's not a question of "either/or": Newton's Third Law is fundamental to the creation of a lift force. Air must be directed downwards to produce a force in the opposite direction: if it's not, there can be no lift force. Don't be misled by what I characterise as 'The Wind Tunnel Syndrome': think instead of a wing moving through still air. A bumble bee demonstrated this for me years ago in the Model Shop at Rolls-Royce, Bristol. It was flying low over the floor, which had a covering of fine sawdust. The downwash from the bee's wings cleared a little pathway of sawdust beneath its flight path. An aircraft can do the same thing to the cloud tops. There are numerous photos on the internet, which show an aircraft producing a 'trough' in the cloud tops, with the inward/downward curl of the wingtip vortices also clearly visible.

[@wbeaty]

One interesting fact: if parcels are being divided by the leading edge, and if camber and AOA are adjusted in order to cause parcels to recombine at the trailing edge, then this guarantees that the Circulation is zero, and the lift is also zero. So, not only is "Equal Transit Time" a mistaken explanation ...it is also a recipe for attaining EXACTLY zero lifting force! Whenever the "phase-shift" between split parcels at the trailing edge is zero, the lift is also zero.

[@AdairGalloJunior]

At 8:28, I think you cannot assume the density of air to be constant. It certainly is a function of velocity (and pressure). Therefore, the equation cannot be integrated without considering density as a function of v. Can someone confirm this?

[@AdairGalloJunior]

if this was applied to a liquid, I think it would be ok.

[@anibal5824]

Density can be assumed to be constant up to around mach 0.3, where there is less than 5% difference in desniry due to compressibility. In reality, all flow is compressible and density does vary with mach number, which means that bernoullis equation isn't valid, but its just an idealised scenario.

[@mconnah1]

So many interesting comments here! I think it deserves a video on how the pressure explanation is valid with a flat sheet style wing. Which certainly flies. When I was taught aerodynamics for my pilots exam, I was told that Newtonian forces made up 70% of lift, with rest being Bernoulli forces…

[@FlywithMagnar]

A flat sheet style wing can fly. At least, it works for model aircraft with light structure (paper, foam or balsa) and and a relatively large wing area. But it cannot be scaled up. And aerodynamically, it's very inefficient. The idea that Newton is 70% of the lift and Bernoulli contributes to the rest is flawed. Lift is based on the preservation of mass, momentum and energy. Newton's laws of motion is preservation of momentum. Bernoulli's principle is preservation of energy. This video explains it in more detail: kzbin.info/www/bejne/mmXaYnyvaduJg8k

[@go737]

Magmar i ask you :::victor schauberger implosion technology wat it is ???

[@FlywithMagnar]

Schauberger designed a device he called the “Home Power Generator”. By sending either air or water through a spirally coiled channel, the generator should produce a drop in temperature, which would then produce suction, and ultimately, implosion. This should be a source of free energy.

[@fedterotten]

Nice explanation 👍

[@raymondgoubet]

What about aerobatics aircraft with a symmetrical airfoil wing, same shape under and above the wing? Lift created by AoA only, to push some air down?

[@PatrickJWenzel]

Aaahhhh, finally the truth, and guidance on how to explain it correctly. Thank you!

[@dhy5342]

The confusion in the minds of many is in the word LIFT. Showing the high-speed/low-pressure airflow above the wing makes one think that the low pressure is lifting the airfoil when in fact, it's the higher pressure below the wing that is pushing the airfoil upward. Low pressure doesn't pull; high pressure pushes and symmetrical airfoils work just fine as long as the angle of attack is positive.

[@josephcameron530]

Excellent information.

[@travisrodricks5965]

I have recently started looking more into the understanding of lift. I am not an aircraft designer or engineer but an aircraft pilot and a drone pilot and instructor. While i fully understand your explanation with curved wings, what i am now looking to understand is straight or flat wings, for example a paper rocket or plane. Would be most grateful if anyone could help out. Thanks

[@FlywithMagnar]

This video might clarify a few things: kzbin.info/www/bejne/mmXaYnyvaduJg8k

[@cruxader27]

I remember during my training days in flight school when my instructor asked me to explain how airplanes fly. But the thing is, I would explain it to him as if he's a toddler. That was one of the hardest questions I faced in my life

[@Tikcreation]

I learn so many things ....thank you 💎 gem❤️

[@A423-f9o]

Excellent explanation - thank you! When people don't belive that lift is created by a wing pushing air downwards tell them to stand under a hovering helicopter ;)

[@petep.2092]

The question is HOW does a wing push air downwards? Saying "there must be circulation" is not an explanation.

[@jamesmarshall6015]

So if lift is created by the curved flow of air over an aircraft wing, which creates a low pressure area above the wing, how do you explain how a flat-winged aircraft flies? What about a wingless aircraft such as NASAs M2-F1? What about the case of the F-15 jet that landed successfully after one wing was completely torn off in a mid air collision? Lift is being created in multiple ways across multiple parts of an aircraft, including primarily reactions stemming from Newton's Third Law.. Provided the sum of these forces match or exceed the total weight of the aircraft, the aircraft will stay aloft. A typical airfoil shape will maximise efficiency, meaning there is more lift created for a given thrust energy. Curved airfoils do create low pressure areas above the wing, and this adds to total lift, but with sufficient thrust energy an aircraft will fly with completely flat wings or even no wings at all, because sufficient lift is created via the body of the aircraft deflecting air like a stone skimming over the water when thrown at the right angle.

[@realvanman1]

I find the explanation in the beginning to be the best. A wing encountering still air takes that air and moves it from a higher place to a lower place. That requires a force. The equal and opposite force is the lift.

[@jaromirandel543]

Hello. Do I understand correctly that the airflow on the top of the wing "follows" its shape, because when trying to "break away" from the wing, a vacuum is created between the airflow and the wing?

[@davetime5234]

It's not clear if you can say that, because it's not clear how much the mass density changes, considering all of these interrelated effects. It presumably connects the different phenomena better to say the drop in pressure comes from the relative wind's conservation of momentum. The asymmetry causing a constriction to the airflow's path cannot violate the momentum of the flow, so the momentum drops its pressure, to proceed faster. The momentum forces that conservation of energy swap (pressure for speed). This lower pressure turns the airflow at normal ambient pressure down toward the wing.

[@ATINKERER]

I didn't understand your explanation, but I've found a better way for me to understand it. The top of the wing acts like pressure in a large tube entering a narrower section of tube where pressure decreases and the flow is accelerated. The bottom of the wing acts like fast moving air in a narrow section of tube entering a larger section of tube where pressure increases and the flow is decelerated. I would like your evaluation of my understanding of the subject. Am I right?

[@petep.2092]

No, sorry. If the air some distance above the wing was considered immovable, then your explanation for what is happening above the wing would be correct. But then when the wing is angled into the wind, the bottom would act the same and pull the wing down! :(

[@fondueeundof3351]

3:22 If you hold two sheets of paper vertically with a small gap between them, and you blow air down through the gap, the two sheets will clutch. That's the Bernoulli effect. How come with only one sheet of paper the Bernoulli effect is not observable?

[@davetime5234]

I'm glad you brough this up. I had to sort it out for myself. I get what you show with the two sheets of paper coming together and I get what Magnar shows with the curve from holding a single sheet horizontally, with the paper rising. I was puzzled about the single sheet held vertically also. I was not surprised that when I blew, if the sheet did not go with my direction of blowing a bit (if I angle a bit into the paper), it just stayed vertical. And then I thought, "can this make any sense"? I found that the result that Magnar gives 3:11 blowing on the vertical sheet, is a false result. When you are blowing vertically the conditions are much more sensitive to error because your blow direction is parallel everywhere to the paper; but in the curved case it is much more tolerant to error because your breath can't avoid capturing the curve. Try for yourself, but with a very light thin sheet of tissue held vertically. That way you can blow a bit away from it to keep from pushing it in the opposite direction in error. Indeed, the tissue rises toward the blowing air, even when flat. So this has been debunked.

[@shyam6468]

Can u also explain then why water rises in Venturi effect? When we blow air over the top of U-tube containing water then the pressure at narrow region would be smaller I know but it would be smaller than the pressure compared to WODER REGION OF TUBE ABOVE. Why do we compare it to the air pressure inside the U Tube which I static and say that water will rise up?

[@bobstroud9118]

From ‘Stick and Rudder’. It’s all about angle of attack to the relative wind.

[@SoloRenegade]

Stick and Rudder is a Great book, but it gets a bunch of things wrong too, given how old that book is and how little was understood about certain concepts it's to be expected.

[@karlbarlow8040]

Only the angle of attack explanation works when a 'plane flies upside down. Since 'planes can fly upside down, any further debate is pointless.

[@arnobozo9722]

The first video was good. :) This one is poor ! :( I am surprised with the Cambridge professor :( The explanation with stream curvature is wrong. @5:50 note that the cross section between A and B has narrowed since the front of the stream. Because the mass of the stream is constant, the speed through the cross section must increase. That is why the stream accelerate when you have this curved shape.

[@davetime5234]

Continuity of mass flow rate is both under-considered and crucially important, I think. But it's not quite as simple as you explained: how do you explain a flat shaped airfoil producing lift due to positive angle of attack. In such case, one might question, where is the cross-sectional narrowing occurring (top vs bottom), and how much for each?

[@arnobozo9722]

You must not take the point A like @5:50. Look @0:22 and take a cross section when the streams split, and look a small cross section for the up part, and do not take a wide cross section but stop it a little above the airfoil. You see that the cross section is narrowing very quickly. That means that the acceleration above is very important. If you have a flat shaped airfoil, this narrowing is still true. At the trailing edge, the narrowing of the cross section is under the airfoil, yet this narrowing is less violent and the stream can deviate downward.

[@davetime5234]

@@arnobozo9722 I appreciate roughly where you are going with this. But I was also thinking in terms of people who give the counter argument that the bottom looks more like a venturi/Bernoulli constriction than the top. Ideally, I was trying to come up with an intuitive "one-liner" (or two), to put such arguments quickly to rest. I mean, it's clear that the speed is in fact higher on top and lower on the bottom (also in keeping with circulation being clockwise for an airfoil cross-section moving to the left). In the usual introductory conception of "Bernoulli" there is only one path that the air can go, so the mass flow continuity inevitably drives speed up (and for conservation of energy) pressure down. But with the wing you still have "Bernoulli" conservation of energy and mass flow rate to face, but there are now two competing paths... Any ideas?

[@aram5642]

The diagram at 5:46 contradicts that at 4:44 where the higher pressure was on the outside of the curve. So I'm not getting this explanation, sorry.

[@Ozbird-72]

So put that into reverse: Lift is created by deflecting mass. Drag can be optimised by giving the "flat wing" a profile. A non optimised profile will cause airflow separation and therefore more drag. So keeping the airflow on top of a wing is great to improve lift and reduce drag. Simplez

[@enbinzheng-line]

Many pilots, although capable of piloting airplanes, do not truly understand lift. Simply put, lift is as follows: Assuming our Earth is an ideal sphere with no friction or atmosphere on its surface. We also have an ideal small ball placed on the surface of the Earth, which will exert pressure on the Earth due to gravity. If we move the ball in one direction along the Earth, we will find that the faster the ball moves, the less pressure it exerts on the Earth. When the speed of the ball reaches the appropriate size, the pressure of the ball on the Earth will be equal to zero. Why? This is because the surface of the Earth is curved, and when a small ball moves, it tends to move away from the Earth's surface along the normal direction of the sphere. That means the ball is trying to leave Earth. However, due to gravity, when the speed of the ball is relatively low, it cannot reach Earth. But the pressure of the ball on the Earth will be reduced. Lift is also the same. When air moves along the upper surface of the wing, due to the curved surface of the wing, the air also tends to move away from the upper surface of the wing in the normal direction, so the pressure of the air on the upper surface of the wing is reduced (similar to weightlessness). So there is also lift on the surface of the wing. Of course, the lower surface of the wing also generates lift, but the lower surface is opposite to the upper surface and can cause overweight, resulting in pressure higher than atmospheric pressure. This also contributes to lift.

[@henrydevelopment]

F=m.a, or F=m.dv/dt; dv is a vector quantity which includes a change in direction, hence lift from curvature. Not the full story, but certainly a significant factor.

[@petep.2092]

What obligates the air to follow the curvature?

[@HankHarjes]

Bernoulli's principle only applies in a closed volume! Lift is simply provided by the bottom of the wing deflecting the airflow downward. Newton's 3rd law of motion is the primary cause of lift.

[@jaromirandel543]

What if I have symmetric or flat wing? Just like aerobatic aircrafts have?

[@FlywithMagnar]

Angle of attack. kzbin.info/www/bejne/mmXaYnyvaduJg8k

[@jaromirandel543]

@@FlywithMagnar So is this video appliable to flat wing?

[@davetime5234]

@@jaromirandel543 The problem is, you can't get rid of Bernoulli. Lift is caused by asymmetry of a solid to the relative wind. Asymmetry has a contribution from both any designed asymmetry in the camber and asymmetry due to angle of attack. Flying inverted or flying with a flat wing (like a toy airplane), relies on angle of attack to provide the asymmetry. Bernoulli is the conservation of energy related pressure drop, associated with this asymmetry. Asymmetry is the cause of constricting the airflow path more on one side of the wing than the other, which causes the conservation of energy pressure drop response. The force of this pressure drop response forces a bending of the relative airflow downwards.

[@DumbledoreMcCracken]

Only need to know three things: the static pressure difference between the top, and bottom, of the wing is what holds up aircraft (dynamic buoyancy); the wing stops flying when the critical angle of attack is exceeded, regardless of airspeed (stall); and a headwind is much more harmful than a tailwind is helpful (fuel starvation).

[@Milesco]

If you're taking off or landing, a headwind is much more desirable than a tailwind!

[@jelisontejada1758]

Great explanation 👍👍

[@dronemonkey2038]

What about angle of attack….What about wings that have no camber? Perhaps a partial explanation in a very good video.

[@FlywithMagnar]

The angle of attack is a very important factor for lift. Check out this video: kzbin.info/www/bejne/m2WWnWWMlLJ5f7s Wings without camber can produce lift. Again, the answer lies in the angle of attack. But a wing without camber will have poor stall characteristics.

[@scottriddell7893]

@@FlywithMagnar All modern aerobatic aircraft have fully symmetric airfoils as do boat keels and rudders. Some have good stall characteristics others not.

[@henriksegercrantz362]

With an airplane wing the air is not flowing over the shape but the shape is flowing through the air. In a wind tunnel and with a sail, the first is basically true. We talk about two different interactions here.

[@alexkuiper1096]

really interesting -many thanks

[@CrayCraigie]

This is science. Thank you.

[@tyronefrielinghaus3467]

The How do wings work? Holger BabinskI article is behind firewall☹️☹️☹️.

[@FlywithMagnar]

Email me and I will sent it to you. You'll find my email address in the About secion in my profile.

[@tyronefrielinghaus3467]

@@FlywithMagnar thanks ..I ought to have searched first...I've got the pdf now. Great channel btw. I'm on a farm that uses a Grand Caravan for yellow metal parts delivery... so trying to get up to speed with the basics 😊.

[@steveststst2968]

A water ski produces lift by deflecting water downward. No water flowing over top.

[@geromiuiboxz765]

🇨🇱 Right ! In trying to get the historic confusion straight, he used a curved airfoil diagram. It would have given a much better insight, if he used a plain [non curved!] sheet for explanations and flow /force diagrams. Just like the water ski 👍😀. The curving and asimetry of a foil is not needed for "lift", but for reducing drag ‼️ Saludos de 🇨🇱

[@jmevb60]

Planing motorboat I suggest is a different phenomenon that fluid flow around the non planing boat

[@pompeymonkey3271]

To me, the aerofoil can also be thought of as the most efficient shape required at the chosen AoA. Certainly your description of airliner wing profiles fits this logic?

[@johnspathonis1078]

Can you please explain how planes with symetrical wing profiles can fly either right way up or upside down.

[@FlywithMagnar]

Sure, the answer is to apply a positive angle of attack. Please watch this video: kzbin.info/www/bejne/mmXaYnyvaduJg8k

[@redbaron07]

@@FlywithMagnar Related, I recall learning somewhere that "the top surface provides 2/3 of the lift, the bottom 1/3, and that is why we hang engines on the underside of wings". That debunks the "air bouncing off the bottom" as the primary origin of lift. Can you explain that with the "curved streamline" model though?

[@Robert-d5l]

If you move air upward then downward then back upward to retain it's original trajectory, you'll build a force within the object that can't be used for lift. You have to accelerate air downward and expend it. This downward movement of air can't be recaptured , that would eliminate lift. You don't cause a pressure differential and get lift. Rather a pressure differential IS lift caused by accelerated air. To be sure, try recapturing the downward accelerated air,no lift will happen.

[@davetime5234]

A weak explanation repeated many times does not equal a strong explanation. The only solution is to study physics in greater depth under competent supervision. I'm sorry, but this is the truth. You've stated your case. Now go back to the books and study to increase understanding. It's ethically the correct path is it not?

[@sverigeaao5196]

Hej! Kul initiativ!! Rekommenderade dej i kommentarerna till 3greens videor. Mycket bra australiensare!

[@FlywithMagnar]

Tusen takk!

[@grejen711]

Hmm... I've always found the easiest way to "explain" lift to a lay person (non engineer/aerodynamicist/mathematician) is to have them try to handle a full sheet of plywood in a stiff breeze. Makes it really intuitive, especially if you're standing on a roof at the time. The air has mass. On it's way past objects it pushes them around. Now if you want to start creating a shape that has a particular and specific behavior as it moves through the air... that's more complicated.

[@FlywithMagnar]

A sheet of plywood held in an angle against the wind is like an airbrake. There's a lot of resistance, but little lift. That's why wings are shaped as they are.

[@crimony3054]

@@FlywithMagnar Moron. A sheet of plywood is a wing. The air molecules hit against it like ping pong balls and force it in one direction or the other. More efficient wings exist, as early aerospace engineers discovered.

[@petep.2092]

@@crimony3054 For being rude, you get to explain… so what makes for a more efficient wing?

[@Ozbird-72]

Lift is created deflecting a fluid mass. Drag and deflection efficiency can be modified by shaping the surface into an "airfoil". Simplez

[@jimbo2629]

You say the air speeds up over the convex surface, but why. What is providing the force? Granted if it does speed up, which it does, then the pressure drops. But where is the force causing this acceleration. Your explanation is incomplete.

[@crimony3054]

It speeds up because the pressure drops. The acceleration/ pressure dynamic is sort of a chicken and egg problem, but prior to the air hitting the leading edge, there is no acceleration. Hence, the pressure drop forces the speed to accelerate. It's like a Venturi, but the top half of the Venturi is composed of air that can't get out of its own way. You have to have a good leading edge design and a high wing velocity in order to make air so resistant that it works like the top half of a Venturi. But with that, some aluminum, kerosene, and human enginuity, you can lift a 747.

[@dukeluisf15]

Your video should have more views, my aeronautics bachelors degree don´t understand this, and many of the faults are the FAA and his technical publications

[@dronemonkey2038]

Is the low pressure the lift or is it the turning of the airflow downwards? The change of momentum inducing an upward force on the wing. So the change in pressure toward the centre of the curve ensures the flow stays attached.

[@FlywithMagnar]

Lift can be described as the difference in air pressure above and below the wing. Lift can also be described as air being pushed down by the wing.

[@dronemonkey2038]

@@FlywithMagnar it cannot be both…

[@FlywithMagnar]

To explain lift properly, you need a degree in science. The explanations I am showing here are more like metaphors that can be understood by laymen.

[@dronemonkey2038]

No Magnar, you don’t, just a curious mind…and to look in a lot of places. kzbin.info/www/bejne/l5KVnHWQdtSLnZI

[@plaenog]

2:50 going down but this is "lift" :/ I am lost in here.

[@JeanLucCoulon]

A flat plate in a stream, if it presents an angle with the stream, also generates lift. This explanation, which relies on a curvature, does not allow to explain that.

[@ATINKERER]

You don't mean that it's all about centrifugal force? I've never heard anyone suggest that centrifugal force is what causes lift.

[@reyadv160]

Wow i love this...thank you sir

[@animatem]

@Fly with Magnar ok. I am interested and I and watched your video more than once. I like your explanation of "pressure" difference. There are however, 2 things that still give me "question". I have 2 observations for you. 1.) I tried your experiment. I confirmed your results. BUT, I also blew on the underside of the paper and it moved up. It didn't matter top or bottom, the paper moved up. Why? 2.) a sailboat's sail is like a piece of paper. It is thin, etc. The length wind travels over the "front" of a curved sail is practically the same as the length traveled on the "back" of a curved sail. The fastest a sailboat will sail is straight downwind where the full area of the sail is exposed and curve in the middle. Think about that. Why does everything on a sail with regards to cause of pressure difference change just because an angle was introduced? How sure are you that "angle of attack" is not more important than curved shape? What are your thoughts? What experiments with paper can you think of to help? I am probably waaaaay out of my league here, but I am honestly curious. I do sail, and as I sail downwind I think about these things.

[@FlywithMagnar]

1) Blowing on the top of a curved piece of paper doesn't explain lift, but the Coanda effect, which is utilized in some aircraft to control the boundary layer. As you see in the video, when the paper is hanging straight down, is will not move when you are blowing over the one of the surfaces. When you are blowing at the underside of the paper, it moves up because you add more air under it. To explain lift, you must look at the entire wing, not only one of the surfaces. So, I suggest you to forget paper experiements. The sail of a sailboat is a better comparission because it reembles the wing profiles of birds and early aircraft. 2) When the wind is blowing along the sail, it will be flapping and not producing lift. When the wind is blowing into the sail with an angle, the sail will form the shape of a curved wing, and it will produce lift. The mast is round and acts as a leading edge. This helps directing the airflow over the curved sail. The curvature of a wing enables it to produce lift without too much drag. Varying the angle of attack allows the wing to produce lift at various speeds. I hope this helps.

[@animatem]

@@FlywithMagnar got it. ...and thank you for the detailed reply. Not many people do that!

[@animatem]

@@FlywithMagnar Really, I want to give a second "thank you". It is nice to have an expert to answer a few of my observations. I know I barely understand these concepts, since my study is rudimentary and mostly based on single paragraphs about lift in sailing books along with a 1980's science textbook. Thank you.

[@alans172]

@@animatem You might enjoy my Swept Volume Theory. Enter swept_volume_theory into your "favourite search engine".

[@alans172]

@@FlywithMagnar Stick with flying. Sailing is much more nuanced. The mast does not "act(s) as a leading edge" at all. It is there to support the sail, and its essential thickness (for compressive strength) does that at the expense of the efficiency of the sail. That's why high performance boats have streamlined, rotating masts ...specifically to reduce the drag from the mast.

[@mitchellcarroll9075]

Hello Magnar, I'm a university student in an aeronautics course doing an assignment involving correcting and/or fleshing out explanations for lift. This explanation is excellent and probably the best youtube video I have reviewed for this assignment. I was pleasantly surprised to hear that you actually were informed by Babinsky, one of the academics my class discussed in learning about the intricacies of airfoil lift. I thought your video summarized his paper well and even explained some of his points more clearly and concisely than the paper did. I just wanted to add one or two points to add my knowledge to what you explained in the video. Firstly, I wanted to clarify what the Coanda effect is as the paper is a good demonstration of this but I thought some people could be led slightly astray by its use here. While the pressure gradient caused by the curvature of the air flow does likely contribute some to the observations Coanda made his research was very specifically about powered jet flows attaching to convex surfaces. Unlike in most explanations for lift of an airfoil which ignore viscosity as the bulk of the math on lift still holds even without viscosity, the Coanda effect does critically include viscous effects. The reason this matters is that a powered jet generates a lot of turbulence which mixes and draws in the surrounding air to sustain the flow and as the jet gets closer to a surface it draws out more air than can be replaced generating a vacuum that suck the jet to the surface. This is a similar effect to your description of why airfoils have lower pressure on their upper side but critically different due to the importance of the mixing of air due to viscosity. Secondly, I just wanted to mention as it was a point of emphasis in my education about this, the velocity and pressure should never be treated as a cause and effect, this is not a mistake Magnar made but one that anyone attempting to explain lift correctly should avoid. The pressure and velocity changes happen together, codependently and at the same time, like an ice cube melting and your counter getting wet, they're related but happening at the same time.

[@FlywithMagnar]

Thank you so much for your feedback. I am humbled. Regarding the relation between velocity and pressure, I learned somehing new! This subject is like discussing who came first; the chicken or the egg. This video received attention from people arguing that a flat wing can fly. So, I made a video addressing just that. kzbin.info/www/bejne/mmXaYnyvaduJg8k

[@BIG-DIPPER-56]

Very Good - Thank You ! ! 🙂😎👍

[@enbinzheng-line]

The understanding of Coanda effect in this video is also incorrect. Coanda effect also works for blowing vertical paper. Because the Coanda effect is associated with the viscosity of fluids.

[@The0ldg0at]

The reality of flying is not just lift, it's the lift vs drag ratio.

[@roiq5263]

I always had a bad feeling about the bernouille principle theory.

[@ShadowRap-y5l]

Hi Captain, which part of your previous video did you made the error?

[@FlywithMagnar]

First of all, I made it too complicated. And I forgot to tell that the updraft is a result of the angle of attack.

[@ShadowRap-y5l]

@@FlywithMagnar thank you for your reply. Out of topic but what do you think is a good weakness to give for an pilot interview?

[@tonybutler3502]

I used to hate the drawings showing the airflow being forced to go faster across the top of the wing and then joining up with the slower flow under the wing, my brain used to ask how the hell do the individual "packets" of air above and below the wings know how to combine again after the wing has functioned. Quantum physics maybe?

[@FlywithMagnar]

Not even quantum physics can explain that!

[@grizwoldphantasia5005]

I always thought that was the easy way to explain lift, probably because I am neither pilot nor aeronautical engineer. Look at the picture of a thin wing at 6:00. Air is lazy, and nature abhors a vacuum -- that is why winds rush in one way only. The air moving over the top has further to go than the air moving below the bottom for them to meet again at the trailing edge. There are two ways to make up this difference: the top air can move faster, or the bottom air can curl up and reverse direction at the trailing edge. It should be obvious that reversing direction like that would be a lot more work, and air is lazy -- easier for the bottom air to keep going backwards and create that lower pressure zone which can suck in the upper air -- speed it up, make the upper air move faster. This difference in pressure is what provides lift. A wing generates more lift as the angle increases, because the difference in distance increases. But at some point, you raise the angle too much, and suddenly it is easier for the bottom air to curl up around the trailing edge and go forward to meet the upper air, and that is how wings stall. This explanation has satisfied friends, but it should be obvious why I am not an aeronautical engineer :)

[@jackfrost2146]

@@grizwoldphantasia5005 Using the intermittent smoke streams, it has been shown that the flow at the top of the wing doesn't meet at the trailing edge. The top flow lags behind.

[@ATINKERER]

I'll have to watch this a few more times to understand that A, B, C, & D thing. Thank you for the lesson!

[@leonardgibney2997]

I would ask how such a wing could fly upside-down. My take on it is at take-off roll a wing has leading-edge flaps extended downwards which has the effect of thickening it. At V1 the air can't get out of the way quickly enough and gets bounced upwards. But it then comes back down again because of the weight of the atmosphere pushing down on it. This has the effect of creating a vacuum above the wing otherwise known as a 'shock wave'. Vacuums have to go where vacuums belong, to the top of the atmosphere (equilibrium law). All trillions of tonnes of the atmosphere pushing the vacuum upwards, but practically it's just the air immediately around the plane which does the job. I've seen these shockwaves above the wings of planes as they say, landed at airports with condensation forming along them. At higher speeds above 400 knots maybe, the shockwave starts to have difficulty keeping up with the plane and drags back on it. Engineers eliminate much of the drag by angling the wing back into the shock wave. This 'sweep angle' can tell you the rough operational speed of the plane. When a plane breaks the sound barrier the bang is caused by the shock wave, no longer able to keep up with the plane, collapsing or imploding. A thick wing will create more lift than a thin one but also more drag.

[@RyanNX211]

Circular airflow and Coanda.

[@charleswesley9907]

Air has weight ! The Centrifugal force exerted on the air following the top curvature of the wing at high velocity supports the negative air pressure that creates lift on the top of the wing . That boundary layer across the wing doesn't lift by magic . It has to be anchored to something . High velocity air has weight . A simple leaf blower should demonstrate that. A wing does have down wash , but that is not where lift comes from. How could you calculate your CG if that were true ? Vacuum caused by the high velocity air molecules trying to adhere to the top curved surface of the wing along with any planning effect from the bottom of the wing is the source of lift . When the angle of attack increases to far the flow of high velocity air across the wing detaches . Not one explanation discusses that High Velocity Air Molecules have a density and weight and deflecting air around an airfoil top surface creates kinetic energy for example Centrifugal Force . That force is where the most of the lift comes from and is transmitted to the top surface of the wing through the iconic Boundary Layer creating a vacuum on the top surface of the wing .

[@edwardmacnab354]

a piece of plywood in a moving airstream will lift if any upward leading edge angle is introduced

[@FlywithMagnar]

I have a video about just that: kzbin.info/www/bejne/mmXaYnyvaduJg8k

[@dr_jaymz]

You stick a plank out into the breeze as you drive along, you get lift. It doesn't have a curved surface but doesn't need one. Its still causing the curve or acceleration of air mass downward. Bernoulli gets too much credit for what is really just a special case of the coander effect. His equation only relates to a stream or venturi but that's really just an aerofoil curled right round to join itself. Coander is all you need and you accelerate any mass you need a force. The force of air moving downward is equal and opposite to that on the wing seen upward. I can believe that in flying syllabus books you still see bernoilli and the equal transit nonsense, I don't know why because its far less intuitive as well as wrong.

[@vincentlee2460]

Nothing wrong with admitting a mistake. It takes courage

[@terencew3840]

feel vindicated .. back in 2000 i was taught the old theory in school and i had a debate with my teacher about the illogical explanation of why the air over the top of the wing meeting the bottom air at the same time doesnt make sense at all

[@yochanan7747]

Great vdeo! thanks!

[@SaeedAcronia]

1:41 You just used Newton's first law of motion right there. So, yeah. There's no escaping Newton's laws when it comes to macroscale motion.

[@shapegroove]

Just a note, "deceleration" is incorrect. It is always called acceleration, simply because acceleration is a vector, so it has magnitude and direction. Like the difference in speed (scalar only) vs velocity (movement with direction)... The same goes for electric circuits, there is NO CURRENT FLOW, only directional movement or jostling (oscillation) of charge (DC vs AC). Hence current NEVER FLOWS, current is a form of flow AND thus, CHARGE is what moves. Current flow is nonsense, can a flow flow? (second derivative of what??) In the same sense, acceleration is the ONLY term and when a car, for instance hits the breaks, it accelerates to a HALT. Because the acceleration vector changes direction to oppose the motion, via the breaks and friction exerted on the road.

[@yl9154]

Thank you!

[@glider1157]

My explanation: A curved wing is interrupting the air-pressure over the wing in a narrow area causing lift.

[@riosabadicci4380]

Why would interrupting airflow create lift? Does a fan fly?

[@oleringstad6615]

Helt super forklaring!

[@fredbarnes196]

It seemed like an arbitrary decision to compare lift to low pressure cyclones. Why not compare lift to high pressure systems? That would make the pressure highest in the center of the system and lower as you moved outward, reversing the conclusions of the discussion

[@VicAusTaxiTruckie]

Yeah Babinsky is wrong. It is not the curvature, it is the reduction of the sectional area of the streamline when there is a physical obstruction of the wing in the free stream. In theory, the streamline geometry would be symmetrical, causing symmetrical pressure distribution, and zero lift possible. However, boundary layers and BL seperation exist in nature, thus allowing a wing to alter streamline geometry to allow net lift.

[@FlywithMagnar]

I have to say that you are bold challenging Professor Babinsky. Even if you have a degree in fluid dynamics, you might learn a few things from him.

[@VicAusTaxiTruckie]

@@FlywithMagnar perhaps there might be details lost in the simplification of the explanation for lift, but the fundamental concept is still wrong. It is also NOT about fluid dynamics, because that studies the flow that is already established. The simplest way to explain lift is THE SHARP TRAILING EDGE. Which forces air to flow around the wing in nature in the pattern observed. After which you may apply fluid dynamics.

[@FlywithMagnar]

Well, have a look at this video: kzbin.info/www/bejne/mmXaYnyvaduJg8k This is lift as explained by Professor Holger Babinsky, Associate Professor Krzysztof Fidkowski, and L. J. Clancy's book "Aerodynamics".

[@VicAusTaxiTruckie]

@@FlywithMagnar Already seen it and you are incorrect. Others have already pointed out that a flat plate wing will generate lift, it just generates a ton of drag. The reason why a flat plate can generate lift is it has a SHARP TRAILING EDGE which creates a flow pattern that has circulation. My proof: A flat plate propeller can generate thrust, many fans use flate plate blades to reduce cost. You are also wrong about downwash in your video. There is no downwash because the wing wake is turbulent and has no net vector. Your own pressure distribution diagram shows lower static pressure in the flow that left the top of the wing compared to flow leaving the bottom of the wing. This means the flow pattern will bend UPWARDS behind the wing. Applying Newtons 3rd law to suggest there is a downward change in mass flow in reaction to lift is the biggest damned fallcy of all. It violates the fundamental principle of conservation of energy. The only way this is true is if you always need at least a thrust to weight ratio of greater than one for self powered flight. This is only true in VTOL and helicopters.

[@aviationtalkandtutorials2456]

Great work as usual Captain, but if your audience are mostly pilots not design engineers, so they better stick to the angle of attack principle, as in fact all the controls works the same way, i agree the lift is the product of all these things together but it is easier to visualize the deflections in controls in anticipation of the effect than using the deflection increase method. Keep up the good work capt :)

[@buzzypeterson1147]

In 7000 hours of flight time. Flying cargo for a living, flight instructing, flying ultralights, powered parachutes, and kites. I have come to the conclusion there is not just one answer. Lift comes from pressure, that pressure can come from impact, ie angle of attack, In a powered parachute or kite. Or from Bernoulli’s type of lift. Some aircraft such as the stol planes could fly with no airfoil at all. Just off impact pressure. There’s a lot more to this, like aspect ratio, And drag curves. It’s not that easy of a thing. Nice video. But the whole story has to many answers.

[@HxTurtle]

you've a poor understanding of this subject. while it's too tedious to go through everything, just for starters: symmetrical airfoils such as on aerobatic plans still create lift the exact same way as any other plane; meaning almost exclusively via their top surface. in this case, an angle of attack is required for it to work, but the lift does *not* come from "impact pressure" or deflected drag. while physically not impossible, this would be by far the least efficient method to create lift.

[@ktl4539]

I've never heard a good explanation of how a fully symmetrical wing can produce lift based on Bernoulli principles. A half symmetrical wing is always shown in the standard explanation and talks about high and low pressure. Doesn't make sense. As in any fluid system, the object must displace more fluid to float or fly (PLANE). An airPLANE wing merely displaces air from the wing to overcome the weight of the aircraft. The angle-of-attack allows the wing to displace enough air off and down from the wing to produce the lift. This is what "lifts" a boat moving through the water i.e. when it gets up on PLANE.

[@kalas2320]

You should know that, in aerodynamics, they apply the Bernoulli equation with potential flow. That means the flow is inviscid, irrotational and incompressible. This leads to the Laplace equation with the boundary condition there is no flow normal to the lifting surface. When you blew the paper vertically, there existed flow normal to the surface, so, it didn't meet the boundary condition for aerodynamic external flow. In short, your proof is flawed from the beginning. The Bernoulli equation is based on the principle of conservation of energy of ideal fluid, so, it is the same thing as the Newton's law of motion. We need to know their fundamentals before using them though.

[@davetime5234]

"When you blew the paper vertically, there existed flow normal to the surface, so, it didn't meet the boundary condition for aerodynamic external flow" When he blew on the paper vertical, his blowing technique (because it is sensitive to error in this configuration) gave a false result. Hold a very light piece of tissue paper vertically, and blow with more caution so that you don't force the tissue to be forced in the opposite direction (it's already fighting against gravity after all). There's little question the tissue is attracted toward your breath just like in the horizontal curved case.

[@enbinzheng-line]

There are correct factors in this video, but there are also incorrect factors. Why does air move along the curved surface of a wing? According to my explanation, this is because the upper surface of the wing is curved, so the air tends to move away from the upper surface of the wing along the normal direction of the upper surface, causing the air to be pulled and resulting in low pressure. The video author believes that the reason why air moves along the curved surface of the wing is due to the Coanda effect. The Coanda effect exists, but it is caused by air viscosity, which is different from the reason I mentioned for curved motion. The low pressure generated by the drag of air and the low pressure generated by the Coanda effect are different, with the former contributing more to lift. As for the lower surface of the wing, where the air is compressed, the air pressure increases. This also contributes to the wing lift.

[@FlywithMagnar]

"Why does air move along the curved surface of a wing?" The answer is pressure difference. "The video author believes that the reason why air moves along the curved surface of the wing is due to the Coanda effect." I could have been more precise here. The Coanda effect is caused by a jet of air blowing over a curved surface, as demonstrated by blowing air over a sheet of paper. The Coanda effect can be used to enhance lift, for example by blowing bleed air from the engine compressor over the flaps. However, wing lift is caused by pressure difference.

[@enbinzheng-line]

@@FlywithMagnar I asked: Why does air move along a curve? You answered: This is because of the pressure difference. I asked again: Why is there a pressure difference? You answered: Because the air moves along a curve. It can be seen that you are reasoning in a circle. The correct explanation is my explanation.

[@davetime5234]

@@enbinzheng-line "Why does air move along the curved surface of a wing?" Because the average speed of the random thermal motion of air molecules is about 500m/s. This means that the air fills any available space very rapidly (think of the forces behind rapid decompression). The curved surface is the boundary of movement, and the above average motion in all directions constituting static pressure, fills out with almost instant reaction, toward and along the boundary of the curved surface. So, Magnar is correct in saying "the pressure" difference because random thermal velocity "abhors a vacuum". But when you say: "why is there a pressure difference?" That is a different context for the notion of pressure difference. You're asking about why we measure a pressure drop due to the curve rather than why the air moves along the curve. Clearly, they are closely related, but they also need to be considered separately. The drop in pressure you measure is because the curve elongates the path, but the mass flow rate must continue at the same pace, so the pressure drops until the speed increases enough at that reduced pressure to maintain the original mass flow rate (and this is also consistent with conservation of energy). So, Magnar is again correct.

[@enbinzheng-line]

@@davetime5234 What you said seems to be wrong. First there must be an increase in space, and then there will be air molecules to fill up the increased space. In other words, there must be a pressure difference first, and then there will be air molecules to fill up the space. So where does the pressure difference come from?

[@davetime5234]

@@enbinzheng-line Not a pressure difference first. And not an increase in space, not in aggregate anyway, because you are inserting the airfoil to decrease the available space after all. The asymmetry of the airfoil constricts the available path for airflow, more so on the top than bottom. So, if you're going to talk about what comes first, it is asymmetry to the relative wind. Second (rather than first) is the pressure change as a response to asymmetry as the relative wind acts to preserve its properties of conservation of mass (flow rate), momentum and energy. Third, is some of the horizontal momentum of air bending to a net change to some amount of vertical momentum ("bent" by the pressure change), which equals the force of lift. Summary: 1)asymmetry 2)pressure response (conservation properties) 3)vertical momentum change (lift as a response to pressure change)

[@bobparis2259]

No mention of angle of attack? No consideration of non cambered wings working in simple toy gliders? If all the lift is low pressure above the wings, what keeps the lift required to carry a 400K pound B747 from ripping the thin skinning off the upper wing surface? There has to be more.

[@lastmanstanding9389]

Take off is Bernoulli while landing is Newton.