The role of water injection on the mixing noise supersonic jet

Abstract

Recent studies indicate that the turbulent mixing noise is the main contributor to the far-field overall sound pressure level (OASPL) in supersonic jets. Evidence from the current investigation suggest that the dominant sources of the turbulent mixing noise are located at the end of the potential core region of the jet. A novel approach using water injection into the jet shear-layers is employed as the noise suppression technique. In contrast to previous investigations, this study utilizes only a small amount (less than 10% of jet exit mass flow) of water to affect the dominant noise producing region. A converging-diverging rectangular nozzle of aspect ratio 4 and a design Mach number of 1.44 is used in this investigation This preliminary study indicates that a minimal amount of water injected at the nozzle exit has produced a modest decrease in the near-field OASPL. The narrow band frequency spectra show that both the shock associated and the mixing noise was reduced by the injection of water.