Is it not wrong as well as inaccurate to assume that all the effects that occur in a venturi will be the same if you were to cut the venturi in half, ie. a wing?
south coast, a very pertinent and insightful question. Answer once again from NASA.
* An airfoil is not a Venturi nozzle. There is no phantom surface to produce the other half of the nozzle. Velocity gradually decreases as you move away from the airfoil eventually approaching the free stream velocity. This is not the velocity found along the centerline of a nozzle which is typically higher than the velocity along the wall.
* The Venturi analysis cannot predict the lift generated by a flat plate. The leading edge of a flat plate presents no constriction to the flow so there is really no "nozzle" formed. One could argue that a "nozzle" occurs when the angle of the flat plate is negative. But this produces a negative lift. The velocity actually slows down on the upper surface at a negative angle of attack; it does not speed up as expected from the nozzle model.
* This theory deals with only the pressure and velocity along the upper surface of the airfoil. It neglects the shape of the lower surface. If this theory were correct, we could have any shape we want for the lower surface, and the lift would be the same. This obviously is not the way it works - the lower surface does contribute to the lift generated by an airfoil. (In fact, one of the other incorrect theories proposed that only the lower surface produces lift!)
* The part of the theory about Bernoulli's equation and a difference in pressure existing across the airfoil is correct. In fact, this theory is very appealing because there are parts of the theory that are correct. In considering the pressure-area integration to determine the force on a body immersed in a fluid, if we knew the velocity, we could obtain the pressure and determine the force. The problem with the "Venturi" theory is that it attempts to provide us with the velocity based on an incorrect assumption (the constriction of the flow produces the velocity field). We can calculate a velocity based on this assumption, and use Bernoulli's equation to compute the pressure, and perform the pressure-area calculation and the answer we get does not agree with the lift that we measure for a given airfoil.