Eli5 what bernoulli’s principles is and how it works for aviation. Been watching videos about it and still cant wrap my head around it, thanks heaps for any help.
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I’ll try to merge a lot of concepts here for one, all encompassing explanation.
Bernoulli’s principle says that flowing fluids exhibit less pressure in directions *other than the one they’re flowing in* (in that direction, things are more complicated). If you want an intuition for this, it’s roughly speaking that the fluid is still exhibiting the same pressure, but now more of that pressure is directed forward instead of equally in all directions.
There’s a common explanation that airplane wings are longer on the top, forcing air to move faster over them than under them because it needs to take a longer path in the same time, and thus generating lift. This is totally wrong. There’s nothing that requires air to take the same time to do this. In fact, air does tend to move faster over the top of wings, but way faster than this theory would suggest.
Flight is complicated because fluids are complicated, but it’s more straightforward and accurate to say planes fly because they push air down. You may have heard Newton’s Third Law: “Every action has an equal and opposite reaction”. That’s what’s happening here: airplane pushes air down, air pushes airplane up.
While Bernoulli’s principle is at play here, it’s more accurate to say that the wing pushing air down is creating the faster flow than to say that the faster flow is lifting the plane. But again, these things are complicated and everything gets an asterisk. But roughly speaking pushing air down requires pushing it forward too, so it bunches up under the wing and goes more slowly. At the same time, this creates a lower pressure region over the wing, since the wing has pushed down air that would have normally gone over the wing. Air rushes to fill this low pressure region and therefore moves faster.
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