Investigation of Twin Jet Aeroacoustic Properties near a Hybrid Wing–Body Shield

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Abstract
In preparation for wind-tunnel acoustic experiments of a hybrid wing–body vehicle with two jet engine simulator units, a series of twin jet aeroacoustic investigations was conducted leading to increased understanding and risk mitigation. An existing twin jet nozzle system and a fabricated hybrid wing–body aft deck fuselage are combined for a 1.9% model scale study of jet nozzle spacing and jet cant angle effects, elevon deflection into the jet plume, and acoustic shielding by the fuselage body. Linear and phased array microphone measurements are made, and data processing includes the use of the deconvolution approach for the mapping of acoustic sources. Closely spaced twin jets with a 5 deg inward cant angle exhibit reduced noise levels compared with their parallel flow counterparts at similar and larger nozzle spacings. A 40 deg elevon deflection into the twin jet plume, which is required for hybrid wing–body ground rotation, can significantly increase upstream noise levels (more than 5 dB overall sound pressure level) with only minimal increases in the downstream direction. Lastly, deconvolution approach for the mapping of acoustic sources processing can resolve the noise source distribution of multiple shielded jet sources within the limits of the incoherent source assumption.

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