Morgan BellHow do planes fly?
January 16th 2009 00:11
Well, that's not the entire story, and the video hints at the other part of the reason: the angle of the wing.
From this presentation by David E. Anderson at Fermilab, we see that the airspeed at the top and bottom surfaces of the wing create a differential in pressure, due to Bernouilli's principle. Anderson notes that this pressure difference only creates a small amount of lift, certainly not enough to explain a huge metal aircraft in the sky.
What's the other part? It's much simpler to understand, thankfully.
The shape of the wing causes the flowing air to 'stick' to it, like water running from a tap might 'stick' to your hand, or the surface of a glass. This is called the Coanda effect, and forces the air to follow the shape of the wing - at the back, the wing directs the air downwards which, creates lift.
From dmeissler.com:
"On a plane this equates to grabbing the air going over the top of the wing and pulling it snug to the downward sloping wing surface. This redirects massive amounts of air toward the ground, which results in an upward force, i.e. lift."
This makes more intuitive sense... as dmeissler points out, if you stick your hand out the window of a moving car, you can feel the effect of lift from the redirection of air.
I'm thankful for this explanation, which makes the idea of flight easier to swallow... the idea that Bernouilli's Principle is the only thing working for us is a little frightening when you're hanging up there in the sky.
*this image is from the David E. Anderson presentation
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