Flap noise generation and control

The characteristics of aerodynamic noise generated by the interaction of an airstream with a flap surface are discussed. The location and behavior of various noise sources were investigated to determine optimal quieting techniques. A schematic diagram of the jet-flap concepts being considered for integrated-powered-lift systems for short takeoff aircraft is shown. Each of the concepts has in common high velocity turbulent air flowing over relatively rigid surfaces with resultant production of interaction noise. The nature, location, and control of noise sources which involve the interactions of air flows with airfoil surfaces are examined.