The influence of micro-jets on subsonic jet noise is numerically investigated on a single stream nozzle for two testing points. For both ambient temperature and heated jets, the acoustic Mach number M_a = V_j/a_o is fixed to 0.9. 12 micro-jets are regularly positioned around the nozzle lip, with a impinging angle of 45 degrees to the jet axis. The velocity is fixed to 300 m/s and the static temperature to 288 K. LES computations are performed for the jet aerodynamics part, with a MILES approach. Acoustic propagation is assured with the Ffowcs-Williams and Hawkings surface integral formulation. Discussions are made on the reference mean flow results compared to experiments, with an analysis of the far field spectra. Computational results present an over-estimation of the mean turbulent kinetic energy and, consequently, an over-prediction of the far field noise. Micro-jets computations are then compared to reference test cases, both aerodynamically and acoustically. Mean flow and spectral modifications are discussed. In accordance with the experiments, their effect on the turbulent kinetic energy is a local increase at the nozzle exit and the delay of the appearance of the maximum level in the jet development. A maximum reduction of 2 dB is obtained at 90 degrees for both temperatures.
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