The thing I never found satisfying was this notion that the air over the top moves faster because it has further to go - in what way does the length of a path that lies in the air's future have any effect on its speed now? As if the air over the top somehow has to match up with the air it was next to before the wing split it away below? What mysterious force would account for that?
The best I could arrive at was that the forward motion of the wing causes the back side of the curved wing top simply to pull away from the air in that region, reducing the pressure there, and incidentally (because Bernoulli) that air then moves faster as a result.
>The thing I never found satisfying was this notion that the air over the top moves faster because it has further to go
On the one hand I agree that it is a stupid way to phrase it. On the other hand if the air doesn't "make it" then there is nothing where the wing just was aka a vacuum. The low pressure area that forms above the wing sucks the air along making it faster. Why doesn't all the air rush to fill the low pressure area? Well for air below the wing there is a wing in the way, air above the air flowing over the wing does rush down to fill the void providing lift, air behind the wing does as well creating some drag.
Same for angle of attack it deflects the air that would normally be above and behind the wing down (providing some lift),making a low pressure area form above the wing which the air speeds to fill.
> air above the air flowing over the wing does rush down to fill the void providing lift, air behind the wing does as well creating some drag
Just a nitpick, but these forces are never pulling, only pushing. The air rushing to fill the voids is not pulling the wing, is the air below or in front if the wing that pushes (and doesn't find an equal push on the other side).
Imagine I fill a bathtub full of marbles - and I pull a solid semi circle through the marbles. The marbles that flat side moves past will barely have to move, the marbles that are displaced by the round side will have to 'move further'. They won't come out exactly at the same time, but they will have had to move further and move faster as the semi circle moves through the bath.
I guess you could do the same thought experiment with foam/sponge balls in a bath - no matter if they squeeze, they will still be moved out the way and follow the path of the semi-circle shape.
The speed of the wing is what causes the air to move around the two faces of the wing. The air has to move around the wing as it is being pulled through it.
Imagine pulling a fixed walled tube though the air, the air will move through the tube at roughly the speed that the tube is pulled through the air.
Now imagine pulling a funnel that starts off large and gets smaller. The same air will now have to move faster to get through the funnel (higher pressure at the mouth of the funnel, lower at the end).
The best I could arrive at was that the forward motion of the wing causes the back side of the curved wing top simply to pull away from the air in that region, reducing the pressure there, and incidentally (because Bernoulli) that air then moves faster as a result.