Reduction of Noise Generated by a Half-Open Weapons Bay

Abstract

Three passive methods for reducing the dynamic pressure loads and noise inside a complex weapons bay were evaluated at flight Mach numbers of 0.75 and 1.5: a leading-edge fluidic spoiler, a porous aft wall pressure relief system, and longitudinal baffles. Two open-bay door configurations were considered: both doors open and the outboard door closed. The partially closed case produced broadband and tonal noise levels up to 20 dB higher than the fully open bay. At Mach 0.75, a noise suppression method employing both a longitudinal baffle and the fluidic spoiler at a flow rate of was found most effective with overall sound pressure level reduction of 16 dB, and a dominant tone reduction of 15 dB. At Mach 1.5, a suppression method employing both the fluidic spoiler and the aft wall suction was found most effective with overall and tonal reductions of 10 and 15 dB, respectively. Analysis of the spatial distribution of the pressure in the bay was performed using proper orthogonal decomposition, and it demonstrated that the effective suppression did not alter the distributions, which corresponded to those typical of open cavity flows.