How Wings Work And Create Lift - Bernoulli's Principle

Bernoulli’s Principle explains lift as well as it needs to. However many claim the only and acutal way of explaining lift is using Newton’s 3rd Law of Motion. While Newton’s 3rd Law of Motion method of explaining lift demonstrates lift as well as Bermoulli’s principle method, neither is better than the other. The cause of this confusion is due to the Equal Transit Time Theory, which we now know to be false. Once you realize this and why the Equal Transit Time Theory was never needed, you will understand that Bernoulli’s Principle method of explaining lift was never wrong.

00:00 - Intro
00:11 - Bernoulli's Principle
00:37 - Equal Transit Time Theory
01:55 - Air is constricted above wing
02:16 - flat wing and upside down wing problem
02:56 - Newton's 3rd law and Bernoulli's principle both explain lift

#wings #airplanes #lift #newtons3rdlaw #newton #bernoulli #bernoulliprinciple #bernoulli'sprinciple

[Robert-fs]

The bernulli principle doesn't cause lift. A pressure differential doesn't cause lift. A differential is lift. It's cause is deflected air. No deflection equals no lift.

[annoyingbstard]

I would point out wings are not “sucked” upwards by low pressure but pushed up (from below) by higher pressure.

[EHerobrineE]

Thank you for this! It's very easy to understand :)

[jeffreyerwin]

Bernoulli applies to the flow and pressure of a fluid that travel though a pipe of varying diameters. A sail is an airfoil that produces lift, yet it has exactly the same length on each side.
Newton's laws of motion fully explain the pressure differential between the two side of the sail without any help from Bernoulli. And there is no "constriction" on the lee side of a sail.

[PromoJetAus]

Hi Guys - great video style - can you please tell me what software you used? I am interested in creating as well and looking for the best solution. THANKS

[david_porthouse]

When an aerofoil starts from rest, flow at the trailing edge apparently needs to double back round it to join the rear stagnation point. However the atmosphere is not a superfluid, and so instead there is a flow separation at the trailing edge and a starting vortex is dumped in the flow. Vorticity of opposite rotation is bound up with the aerofoil by the principal of conservation of vorticity, and this generates lift by the Magnus effect.

The starting vortex can be visualised, and a stopping vortex can be seen as well. If we alternately start and stop an aerofoil, a vortex street can be generated.

The conservation of vorticity, or Kelvin's circulation theorem, is a topological principle. Fluid mechanics is a linear subject when we are talking about configurations of vorticity, so we can easily move back and forth between the Magnus effect and the Kutta-Joukowski circulation theorem. A starting or stopping vortex is shed whenever the flow is not complying with the Kutta condition.

Explanations based on Bernoulli or Newton are merely wisdom after the event of the starting vortex being formed. They would not work with an inclined hydrofoil moving slowly through liquid helium.

[alisonxd]

Wow. These are really good videos. Very Fascinating. Thanks for making them!

[bradmcclure]

transit time theory is also false in a tube like a pipe or hose the friction of the surface of the pipe induces a reverse current study chaos theory

[gravitomagneticpower]

Well, you showed the area of low pressure, but forgot that the air travels further and expands back right behind this area (which should slow down the flow according the same bernoulli presumption). This is still happening above the wing surface and should oppositely create an area of higher pressure pushing the wing downward as well. Bernoulli's principle is not a good explanation of the lift. Theoretically if the bottom area had a small jet exhaust to make the wind below travel at the same speed as the flow above, the lift should not be produced anymore according the bernoulli's explanation. But is that true? I highly doubt. The main source of the lift produced above the airfoil is not the speed difference but the direction change caused by coanda effect or by pressure equalization followed by breaking the air by an obstacle... Theoretically an airfoil in long:
shape should also create a lift (of course with a bad efficiency)...

[XPLAlN]

Hi there, I agree with the content of this video. Bernoulli and Newton are not in conflict and equal transit time is the fallacy. But I'd like to make a side point about 'pinching a garden hose'. It turns out the increased velocity is not an example of the Bernoulli Principle. I only found this out quite recently, and clearly the statement requires an explanation to support it, so here goes.
Torricelli's Theorem (a form of the Bernoulli Principle) states the fluid velocity at the outlet of a barrel = root 2gh. The usual simplifying assumptions of inviscid, laminar flow apply. According to this equation, the only variable is “h”, so if you put a hose on the outlet and pinch the end, it makes no difference to velocity and that is the undeniable result of the Bernoulli Equation in this scenario – the velocity varies only with height (mass flow rate will nonetheless vary with outlet area). And yet we know the velocity from the hose actually increases when you pinch it. This inconsistency between theory and observation goes away when the real effect of turbulence in the outlet is accounted for. The bottom line is the increase of velocity from a pinched hose is not due to the Bernoulli effect but rather the opposite – it is due to what Bernoulli does not account for, namely turbulence, specifically the variation of turbulent losses as you pinch the hose and vary the mass flow rate.
A brief explanation for this behavior is that the outlet, be it tap or flange, introduces turbulence which is a de facto 'head loss' so velocity out of the hose is less than predicted using Bernoulli alone (an empirical coefficient is applied to estimate real velocity). But turbulence would go to zero if mass flow went to zero. So, turbulence varies with flow rate hence jet velocity varies with pinching.