In 1800, Thomas Young found that a convex surface deflected a jet of air from a blowpipe.
Some describe the Coandă effect simply as the tendency of an airstream
to stay attached a convex surface.
Adherence to a concave surface does not directly provide lift.
Without a nearby surface, an airstream lowers the air pressure all around it.
When it adheres to a surface, it lowers air pressure only on its open side.
When it adheres to the top of a wing, the higher air pressure on the bottom lifts the wing.
When it adheres to the bottom of a wing, the higher air pressure on the top pulls the wing down.
In flight, the Coandă effect occurs only when the adhered airstream
moves faster than the air above it.
The result of deflecting an airstream (up or down) is separate from the Coandă effect,
See also in The book of science:
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