Noise reduction of a Mach 0.7-0.9 jet by impinging microjets

A global noise reduction of a high-subsonic jet is achieved by experimental use of an impinging microjets system. The microjet velocity relative to the main jet velocity, the longitudinal distance of injection and the number of microjets are the three parameters examined in order to obtain the maximum noise reduction. This optimized microjet configuration is obtained by a balance between low-frequency attenuation and high-frequency noise generation due to the interaction between the microjets and the main jet mixing layer. (c) 2006 Academie des sciences. Published by Elsevier SAS. All rights reserved.