Micro-Jet Flow Control for Noise Reduction of a Supersonic Jet from a Practical C-D Nozzle

A convergent-divergent nozzle similar to those used on high performance tactical aircraft has been built with micro jets at the trailing edge. These micro jets are used to increase mixing in the shear layer between the core flow and a secondary flow. Near field pressure measurements, far field acoustic measurements, as well as PIV measurements have been taken at a core flow Mach number of 1.56 and at a secondary flow Mach numbers of 0.0, 0.1, and 0.3. These results are compared with a baseline nozzle with the same geometry to see what affect the micro jets have on the jet noise production of the nozzle. A numerical simulation of the micro jets has been done using a large eddy simulation. The numerical results are compared with the experimental results. The micro jets are shown to decrease the sound pressure levels for low frequencies and increase them for high frequencies. These effects become more prominent as the secondary flow of Mach number increases. The presence of the micro jets decreases the OASPL of the core flow for most cases. The azimuth direction that benefits most changes from forward observation angles to aft observation angles as the secondary flow increases.