Why No One Can Explain Airplanes

Today's video is a very brief look at the incredibly complex phenomena that is Lift. In short, it's complicated and unpredictable but I hope you enjoy the video anyway.
There are a few concepts I didn't cover in the video that I will mention here:
Angle of attack: Tilting the airfoil has a massive effect on the amount of lift, much more than the shape on its own.
Drag: Lift always comes with drag, the best airfoils maximize the ratio of lift to drag rather than simply maximizing raw lift.
Flow separation and Stalling: With steep angles of attack, or sharp changes in geometry (like the triangle airfoil) flow can separate from the airfoil which greatly reduces the lift and increases the drag.
Cut Wind Tunnel Tests: I had two more wind tunnel tests that weren't included in the final video. The first was a flat airfoil that was supposed to act as a control. Unfortunately, because of the updraft seen in the triangle test, the flat plate experienced some lift. This also caused issues with another airfoil shape which was a rectangle with a semi-circle cut out of it. This was going to act as a counter to the longer path explanation because it is supposed to experience negative lift, but the updraft caused it to move up instead. Essentially, the wind tunnel is terrible and is only for demonstration, not actually proving anything.
Intro Music: Himalayan Atmosphere
by Kevin MacLeod is licensed under a Creative Commons Attribution license (creativecommons.org/licenses/...)
Source: incompetech.com/music/royalty-...
Artist: incompetech.com/
(0:00) - Introduction
(0:15) - Basic Explanations
(1:01) - Terminology
(1:26) - The Explanation is Wrong
(2:33) - Nozzle Explanation
(3:03) - Wind Tunnel Demos
(4:17) - Limitations of Explanations
(4:49) - Outro

[@ConHathy]

You may notice an edit at 4:17. I had another wind tunnel demonstration, but my explanation bordered on misleading so I removed it in October of 2020.
There are a few concepts I didn't cover in the video that I will mention here:
*Angle of attack:* Tilting the airfoil has a massive effect on the amount of lift, much more than the shape on its own.
*Drag:* Lift always comes with drag, the best airfoils maximize the ratio of lift to drag rather than simply maximizing raw lift.
*Flow separation and Stalling:* With steep angles of attack, or sharp changes in geometry (like the triangle airfoil) flow can separate from the airfoil which greatly reduces the lift and increases the drag.
*Cut Wind Tunnel Tests:* I had two more wind tunnel tests that weren't included in the final video. The first was a flat airfoil that was supposed to act as a control. Unfortunately, because of the updraft seen in the triangle test, the flat plate experienced some lift. This also caused issues with another airfoil shape which was a rectangle with a semi-circle cut out of it. This was going to act as a counter to the longer path explanation because it is supposed to experience negative lift, but the updraft caused it to move up instead. Essentially, the wind tunnel is terrible and is only for demonstration, not actually proving anything.

[@david_porthouse]

When an aerofoil starts from rest, flow has to double back round the trailing edge towards the rear stagnation point. If the atmosphere is not a superfluid, then instead of doing this the flow separates at the trailing edge and a starting vortex is left behind on the runway. This starting vortex can actually be visualised.
By the conservation of vorticity, there must be vorticity of opposite rotation associated with the aerofoil and this generates lift by the Magnus effect.
Conservation of vorticity is a synonym for the Kelvin circulation theorem and is a topological principle. Magnus effect is a synonym for the Kutta-Joukowski circulation theorem.
Explanations based on Bernoulli or Newton do not work with a hydrofoil moving slowly through liquid helium.

[@cxob2134]

so me wondering how to optimize airfoils is just stuck here not knowing how lift works anymore.
So back to the Simulation to twiddle with values until Lift goes up an drag goes down.

[@BattlePr0grammer]

I love this channel. Never stop.

[@woutbouckaert7592]

You deserve so many more subs dude this is great.

[@shortclips7052]

At 3:29 and 3:37 there must be an angle of attack to create lift which is not shown, otherwise there is no lift at all

[@ConHathy]

There was not, it's well established that chambered airfoils produce lift at zero aoa. Also this was tested through CFD beforehand which resulted in positive lift for both without an angle of attack