[lowkey]

I commented elsewhere that there is no physical reason why the Bernoulli effect would cause the upper streamline and the lower streamline to reach the back of the wing at the same time - and to my knowledge there is no experimental evidence that it does. I may be wrong about that but I have never seen an adequate rebuttal.

[slavak]

You're right- there isn't, and it doesn't. In fact a parcel of air moving over the top of the wing will beat its counterpart moving below it to the trailing edge. This[1] video has a very good demonstration of this. (Relevant part begins around 0:25.)

So saying that air on top of the wing moves faster, creating a pressure differential and thus lift, is absolutely correct. The problem begins when some people try to come up with an intuitive explanation for _why_ the air would need to speed up. "Because this is the lowest energy state that conserves energy, momentum, and mass" isn't a very satisfying answer; neither is "because this system of PDEs say so"; so they came up with the "equal transit time" explanation, which is simple, intuitive, and completely wrong.

Hopefully aeronautical engineers at P&W didn't actually believe that last bit?

[1] https://www.youtube.com/watch?v=UqBmdZ-BNig

[Cogito]

The streamlines don't need to meet for Bernoulli to apply.

That statement, that the upper airstream flows faster because it has to meet up with the lower airstream, is wrong and easy to disprove experimentally.

So, putting aside that specific statement, re-read the post you're replying to.

The airstream above the aerofoil does travel faster, and there is a lower pressure region there (commensurate with the effect described by Bernoulli), and it turns out that this is a valid way to model the forces involved just as it is valid to model them as a redirection of the airstream.