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Comment by monk_e_boy | Hacker News Reader

Or how wings work.

For anyone thats interested in what the parent is talking about: http://www3.eng.cam.ac.uk/outreach/Project-resources/Wind-tu...

I've had people get like legit upset at me when i correct this.

My god, thank you. I remember as a kid this explanation "the top has to move fast to meet the bottom stream at the trailing edge" always confused the hell out of me. Why do the top and bottom have to meet? How would they know? Even as a 10 year old it confused me no-one could answer this.

Especially for hydrofoils. Makes no sense

That's the now famous Bernouilli vs Newton debate.

Personally, I am in camp Newton. Not that Bernouilli doesn't work, they both give the same results in the end, and they are both a simplification of the "truth" which is the Navier-Stokes equations.

The reason I like the Newton explanation better is that if you start with the Bernouilli principle, it is much easier to come up with the wrong idea. The Newton is straightforward: push air down, plane goes up. A bit shallower but at least, the basic idea is hard to get wrong.

It's reasonable to phrase the working of a wing either in terms of momentum or in terms of a different in pressure between the top and bottom. What's incorrect is when trying to explain the action through bernouilli it's often asserted that the air above the wing must take the same time to transit the wing as the air on the bottom. Not only is this completely unjustified to assume when trying to solve the problem, it's also false in practice: in general air above and below will not pass the wing in the same time, even though the air over the top is travelling faster.

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