In this study, a method for reducing the jet noise of a high-speed jet is presented. An array of microjets was immersed within the centerline of an underexpanded Mach 1.6 jet in an effort to reduce the overall sound pressure level and alter its spectral composition. Based on the mass flux through the microjets and the location of the microjets along the centerline of the jet, reductions of up to 5.81 dB with respect to the downstream direction and 7.99 dB with respect to the perpendicular direction can be achieved. An interesting phenomenon is discovered whereby the maximum noise reduction in the downstream direction is found with injection activated, whereas the maximum noise reduction in the perpendicular direction is found with injection deactivated. Placement of the injection tube within the flow is shown to eradicate distinct tones while flow visualizations depicted a strong augmentation in the jet plume via a modification of the shear layer and the internal shock cell structure.
ASJC Scopus subject areas
- Aerospace Engineering