Misapplication of Bernouilli's principle

[vivesdn]

I do feel that Bernouilli is not the main contribution to lift, but evidence seems to show the opposite. Nevertheless, the Bernouilli equation is based on the energy conservation principle. Are you sure that the air flowing above an below a wing must conserve total energy?

 

[Drasnian]

I couldn't find any reference in this thread to the Coanda effect. The Coanda effect is responsible for a wing generating lift, and is the same principle at work in the bathroom sink that causes a thin vertical stream of water to bend around an object placed nearby.

The Bernoulli effect plays no part in generating lift.

There exists NO physical principle that states that to joined particles at the front, the one going over the curved top, the other going beneath, has to meet again at the back.
In fact, this is FALSE.

That's right! After a typical aerofoil separates two vertically adjacent particles, the one that passes over the top of the wing meets the trailing edge before the lower particle does. This happens because the curvature of the top of the wing causes the surface layer of air to separate from the layer of air above it (the particles in the surface layer bend downwards as they follow the curved surface of the wing; particles in the layer above don't bend so much). This creates a region of lower pressure over the wing, which causes increased speed of air throughout that region, over the wing. Despite the greater distance over the wing (than under), air that moves over the wing reaches the back first. In other words, air going over the top gets moved horizontally by the passing of the wing less than the air that goes under.

The vertical component of velocity for the combined upper/lower surface layers of air is then downwards as it leaves the wing. Hence, by conservation of momentum, the wing gets lifted up.