Jet-Noise Reduction by Impinging Microjets : An Acoustic Investigation Testing Microjet Parameters

摘要: The effects of microjets on the aerodynamic characteristics a Mach 0.9 high-Reynolds axisymmetric jet are investigated and interpreted in light previous acoustic results. These measurements obtained by means Stereoscopic Particle Image Velocimetry planes normal to axis. Three parameters system varied: outgoing mass flux per microjet, number their layout azimuth main jet. results indicate strong correlation between maximum level turbulence just behind nozzle exit high-frequency noise, previously shown potentially balance benefits for lower frequencies. measured at longitudinal position corresponding half potential core length is also highly correlated noise reduction, which highlighted similar evolution these two quantities regarding microjet microjets. For low values microjets, act independently, contributions reduction retrieved far downstream impinging point without any noticeable azimuthal diffusion.