Clark Y airfoil?

Question

People say that the airfoil provides lift because the camber of the wing forces the airflow above to travel a farther distance than below, and this is true, but I heard something else and I want to know if it is true. I read that the camber of the wing distorts the airflow causing it to flow upward above the wing thus having less contact with the upper part of the wing surface, giving less friction above and more friction below. This causes high pressure below and low pressure above.

Are both true?

Answer 1

yes, both are true and the other folks are correct, but let me give you a practical example that will help it sink in.  You did this when you were a kid.  While driving down the road, put your arm out the window with your hand flat and level; you will feel very little resistance.  Now rotate your hand; thumb upward and pinky downward.   Your arm will go up quickly.  The bottom of your hand is presenting a lot more surface area to the oncoming air, and there is your lift.  The physics of this is that the that the air travels further over the top of your hand than below it; the lower pressure on top causes the lift. It's a simple example but you can see that you have higher pressure under your hand than you do on top.

Answer 2

Yes, that is why on top of the wings are (esp.737) are small strips of metal surface protruding which are called vortex generators to help/direct  the air flow sticking in the upper camber of the wing than flow upwards.

Answer 3

When air flows over and under an airfoil the pressure is reduced on both the upper and lower surfaces due to the Bernoulli effect.  In normal flight it is reduced more on the upper surface of the wing than on the lower surface of the wing, but it is reduced on both surfaces.  The difference in pressure between the upper and lower surfaces results in lift.

The Clark Y, which is no longer common, is not symmetric so it produces this effect and positive lift at a zero angle of attack.  Symmetric airfoils must operate at a positive angle of attack to produce positive lift.

Answer 4

both are tue. Here is something for you :

http://www.allstar.fiu.edu/aero/airflylv...