AEROACOUSTIC ENVIRONMENT OF AN ADVANCED SHORT TAKEOFF AND VERTICAL LANDING AIRCRAFT IN HOVER

The near-field aeroacoustic environment of a 6.02%-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 now 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 confirm that fountain impingement is responsible for the greatest unsteady loading. Under certain conditions, high screech amplitudes produce increased dynamic loads over a large area of the fuselage and wing undersurfaces.