The air goes over the top of the wing faster than underneath,
But at the sharp trailing edge of the wing the slow underwing flow mixes with the fast overwing flow and makes a vortex that actually sucks air over the top of the wing and drives what is called circulation, air well in front of the wing moves up and into the effect. When air splits over top and bottom of the wing, the bottom air reaches the vortex well after the top split air is rolling below and behind the plane.equal forces, there is never just one force/hand pushing/clapping.
HOW IS LIFT GENERATED?There are many explanations for the generation of lift found in encyclopedias, in basic physics textbooks, and on Web sites. Unfortunately, many of the explanations are misleading and incorrect. Theories on the generation of lift have become a source of great controversy and a topic for heated arguments. To help you understand lift and its origins, a series of pages will describe the various theories and how some of the popular theories fail.Lift occurs when a moving flow of gas is turned by a solid object. The flow is turned in one direction, and the lift is generated in the opposite direction, according to Newton's Third Law of action and reaction. Because air is a gas and the molecules are free to move about, any solid surface can deflect a flow. For an aircraft wing, both the upper and lower surfaces contribute to the flow turning. Neglecting the upper surface's part in turning the flow leads to an incorrect theory of lift.
There are many theories of how lift is generated. Unfortunately, many of the theories found in encyclopedias, on web sites, and even in some textbooks are incorrect, causing unnecessary confusion for students.The theory described on this slide is one of the most widely circulated, incorrect explanations. The theory can be labeled the "Longer Path" theory, or the "Equal Transit Time" theory. The theory states that airfoils are shaped with the upper surface longer than the bottom. The air molecules (the little colored balls on the figure) have farther to travel over the top of the airfoil than along the bottom. In order to meet up at the trailing edge, the molecules going over the top of the wing must travel faster than the molecules moving under the wing. Because the upper flow is faster, then, from Bernoulli's equation, the pressure is lower. The difference in pressure across the airfoil produces the lift.
The shape of wing profile is a key. The top surface is longer than the bottom surface in terms of the air flow. If the air flow is laminar then upper flow near to surface must be faster and this results in a pressure drop above top surface. This difference in air pressure causes the lift force.Of course some types of airfoil have symmetrical shape. Here the same effect is reached by tilting the wing.It is a physics for elementary school in at least Slovakia.
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