Downwash

The effect of downwash from a hovering helicopter is clearly visible on the surface of water below.

In aeronautics downwash is the change in direction of air deflected by the aerodynamic action of an airfoil, wing or helicopter rotor blade in motion, as part of the process of producing lift.^[1]

Lift on airfoil is an example of application of Newton's third law of motion - the force required to create the downwash is equal in magnitude and opposite in direction to the lift force on the airfoil. Lift on an airfoil is also an example of the Kutta-Joukowski theorem - the Kutta condition explains the existence of downwash at the trailing edge of the wing.^{[1][2][3] [4]}

See also

• Slipstream
• Wake turbulence
• Wingtip vortices

References

1. Crane, Dale: Dictionary of Aeronautical Terms, third edition, page 172. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2
2. Anderson, John D. (2004), Introduction to Flight (5th ed.), McGraw-Hill, pp. 352–361, §5.19, ISBN 0-07-282569-3
3. "The main fact of all heaver-than-air flight is this: the wing keeps the airplane up by pushing the air down." In: Langewiesche, Wolfgang (1990), Stick and Rudder: An Explanation of the Art of Flying, McGraw-Hill, pp. 6–10, ISBN 0-07-036240-8
4. "Downwash Effects on Lift". nasa.gov. Retrieved 4 March 2015.