I had heard that air travels faster over the top so that a void isn't created, as the air that travels underneath has shorter to travel, but I don't buy that. There's nothing that forces two air molecules at the front of the wing to join each other at the back of the wing.
2007-03-22 06:26:09 · 8 answers · asked by Justin E 1 in Science & Mathematics ➔ Engineering
You're absolutely right and it's a fallacy that some science teachers actually use to explain lift on the wing just like the stuff about pressure differences because of air speed. The way a plane flies is partly because of the wing bottom pushing down on the air and more importantly, because of the fluid dynamics, the air that goes over the top of the wing gets diverted toward the ground at the back of the wing. From Newton's third law, you push something one way and you get pushed the other.
Here's a decent write up
http://www.allstar.fiu.edu/aero/airflylvl3.htm
2007-03-22 06:37:27 · answer #1 · answered by Gene 7 · 0⤊ 1⤋
True but the air that goes across the top has to go some where and it can't just lag behind because the air plane is moving at lets sayin 100 mph... so there is tons of air tryin to travel over and under this wing, it can't just stay there while all the rest of the air is tryin to pass. Just how it works the top air gets forced to travel faster to cross the top cause it's alittle longer makin the bottom of the wing to have higher pressure then the top creating lift. it doesnt have to meet perfectly at then end if it did that would pretty much mean now drag at the end of its path but there is everywhere in a moving plane. So all i can tell you is try to just except the theory.
2007-03-22 06:43:05 · answer #2 · answered by Big Daddy 3 · 0⤊ 0⤋
It's the other way around. It takes longer for the air to travel over the top of the wing (assuming that the wing is shaped as an air foil). The air molecules slow down and there is more "space" between them, causing lower pressure than the air under the wing. The higher pressure under the wing forces the wing up, hence flight.
2007-03-22 06:34:51 · answer #3 · answered by joe s 6 · 0⤊ 1⤋
The top of the wing is curved. In fluid dynamics, as velodity increases, pressure decreases. When the leading edge of the wing cuts thru the air, the air on the upper side is forced to rise as it passes over. The air 'parcel' has a tendency to stay right where it is (body at rest tends to stay at rest, right?). Mechanically, imagine a camshaft turning with the lobe on top. As the cam spins, the follower on top just goes up and down. But it stays in the same place horizontally speaking, because it is attached to a valve guide. Same with the air. The air rises and falls as if the top of the wing was a cam, but horizontally speaking, it does not want to move because it is at rest in the horizontal direction.
Thats why the wing has to be moving fast enough. At slow speeds the air parcel that the wing is passing thru WILL give way and move horizontally. But as the wing speeds up, compared to the speed of the wing, the air cannot go fast enough. It wants to stay in the same place.
I hope this wasn't too confusing.
2007-03-22 07:01:08 · answer #4 · answered by Anonymous · 0⤊ 0⤋
How about - if those molecules over the top don't keep up with those underneath, then a vacuum will result on the top rear of the wing. A vacuum is lower air pressure. Lower air pressure lifts the wing.
2007-03-22 06:56:29 · answer #5 · answered by p v 4 · 0⤊ 0⤋
Under about 250-300 mph, air does not compress.
Therefore, if the top of the wing is curved, it forms a venturi tunnel above the wing (between the wing and the still air), causing air to flow faster.
If you want a really good explanation, see Barry Schiffs' book The Proficient Pilot.
2007-03-22 06:43:51 · answer #6 · answered by Nick D 2 · 0⤊ 0⤋
For the best explanation of aerodynamic lift, how it is generated how it works, and for working models showing the variations in air flow over and under an airfoil which you can adjust yourself go to:
http://www.grc.nasa.gov/WWW/K_12/BGA/Monroe/lift_theories_act.htm
This NASA site explains the 3 incorrect theories of how lift and drag forces are produced, and also the correct way to calculate the forces.
2007-03-22 17:13:06 · answer #7 · answered by gatorbait 7 · 0⤊ 0⤋
they don't have to join each other at the back for the velocities to increase. Nothing states that the increase in velocity is proportional to the increase in distance the air travels.
Check out Wikipedia for more details.
2007-03-22 06:32:40 · answer #8 · answered by Jeremy S 2 · 0⤊ 0⤋