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Once
the circulation flow is established the wing can provide lift. This comes from
the pressure difference between its top and bottom surfaces. Bernoulli's
equation shows that increased velocity in the flow is associated with lower pressure.
The high velocity flow over the top of the wing reduces the pressure
in this location compared to under surface of the wing. The form of the two
pressure distributions is shown in the diagram for a symmetric airfoil with
a 70 angle of attack. Except near the trailing edge, the under surface
pressure is higher than the upper surface pressure and the difference between
these two pressures when integrated over the wing surface and multiplied
by the surface area is the lift force. |
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