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Wings and Lift

by on 27/02/2014
 

How the shape of a wing, or airfoil, creates lift.

A wing shape, or AIRFOIL, happens to be the best shape for producing lift. That is why nature uses airfoils in birds, flying insects, and bats, and why human engineers use them in various types of aircraft.

As a wing passes through air the airflow divides at the leading edge of the wing. Some air goes over the top of the wing; the rest goes underneath. Because of the Coanda effect, the airflow tends to “hug” the outline of the surface over which it is moving.

The air passing under the wing continues on more or less a straight line. This is because the lower surface of the wing is almost flat. However, the air flowing over the wing has farther to go, because the upper surface is curved. To keep up with the air underneath, the air on top has to move faster. But by Bernoulli’s principle, higher speed means lower pressure. As a result, the air on top of the wing must press less strongly against the wing than does the air underneath.

Since the downward pressure on the top of the moving wing is less than the upward pressure on the bottom of the wing, there is an overall upward force. This upward force is called LIFT.

Source
The Worlds of David Darling