Aeroacoustic environment of an advanced STOVL aircraft in hover

The near-field aeroacoustic environment of a 6.02 pct scale advanced short takeoff and vertical landing aircraft is investigated in proximity to a simulated ground plane. The screech and impingement-tone characteristics of twin supersonic round and rectangular plumes are shown to be highly dependent on nozzle geometry and height above the ground plane. Shadowgraph and laser-sheet flow visualization are used to clarify the flowfield mechanisms responsible for time-dependent loads due to screech, impingement tones, and unsteady impingement of the upwash on the fuselage undersurface. Detailed dynamic pressure measurements from an array of transducers on the fuselage confirms that fountain impingement is responsible for the greatest unsteady loading.