How much lift is due to the top parabolic shape of an airplane wing vs the bottom concave lift of air below it?
How much lift (vacuum) is due to the top parabolic shape of an airplane wing vs the bottom concave lift of air below it? Say the rudders are tangential to the top convex part of the wing. Say I laid a 200 pound convex dish with a rim diameter of 7 feet on the ground and it was hermetically sealed, how fast would the wind have to blow in order to create enough vacuum to lift the dish up from the ground breaching the seal?
RossK2015-06-04T23:03:00Z
There are a couple of different theories, one that is the angle of attack that produces all, or virtually all, of the lift. The camber, or curvature of the top surface of the wing allows a significant angle of attack without the air separating from the upper surface as would happen if the wing were a flat plate. In this theory, the camber does not contribute to the lift accept to allow an angle of attack will maintaining a streamline airflow across both upper and lower surfaces of the wing. In an attempt of proof, proponents of this theory cite that some aircraft have symmetrical airfoils, with equal top and bottom camber, and develop lots of lift entirely from angle of attack, and the lift has nothing to do with a relative vacuum created across the upper surface. I believe there is a very small amount of lift generated by the asymmetrical camber of the wing at zero angle of attack, but most of the lift is generated by reaction to the mass flow deflection of the air due to angle of attack.
I think you would need a lot more information, or assumptions, to answer the second part of your question. Modeling this shape and putting it into a wind tunnel would be the only concrete method of determining the lift of this shape.
The top surface of a wing is not a parabola but is any of a variety of curves, mostly non-symmetrical, for providing lift under the design conditions for the plane. It is convex. The additional lift you are referring to on the bottom is normally not concave but is flat but at an angle called the angle of attack. The amount of lift from wind blowing across the convex top surface of a dome will depend on the shape. The rudders have nothing to do with lift as they are vertical.