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Bernoulli Effect



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twinky64

Ok. So I understand the concept of the Bernoulli Effect. Low pressure up top and High pressure down underneath of an air foil. What I do not understand is WHY a low pressure, or a lower pressure w.r.t. the underside of the air foil, is created. I've been told, it's because the air moves faster. If that is the case, then how does high velocity air contribute to low pressure. Seems counter-intuitive doesn't it?

I'm asking in hopes of leamens terms.

I was told that the "leeward" side of the top side of the airfoil creates a venturi like effect. The other is that because velocity is increased across the top, the air molecules have to separate even further creating a low pressure area. If the latter was the case, why arent the tops of airfoils crescent shaped?

On a side note, this is interesting: http://youtube.com/watch?v=qU1fixMAObI

JeremyH

Ok. So I understand the concept of the Bernoulli Effect. Low pressure up top and High pressure down underneath of an air foil. What I do not understand is WHY a low pressure, or a lower pressure w.r.t. the underside of the air foil, is created. I've been told, it's because the air moves faster. If that is the case, then how does high velocity air contribute to low pressure. Seems counter-intuitive doesn't it?

You have it a bit backward. The air moves faster because of the lower pressure. The shape of the wing and/or position with respect to movement creates the areas of differing pressure (if the wing were flat on both the top and bottom and parallel to the motion of the object, no pressure difference would exist and the only result would be air drag). Since these areas differ in relative pressure, air moves toward the lower pressure region. In regard to a wing, this area of lower pressure happens to be on the top, so the air moving over the top of the wing travels faster than that moving under the bottom of the wing. Both of these masses of air are forced downward at the back of the wing which generates lift.

 

I hope this helps to clear up the confusion.