Far-field Noise Prediction of Round and Serrated Jets with Increasingly Refined Grids

Turbulent jet large-eddy simulations (LES) are performed at Mach 0.9 and Reynolds number of 106. For subgrid scale stress modeling the sigma-model is used. Solutions are obtained for a baseline axisymmetric (round) nozzle and a serrated (or chevron) nozzle with high bending and penetration, on grids ranging from 5 to 80 million grid points in order to assess the correlation between coarser and finer grid solutions. Computed mean and second-order fluctuating quantities of the turbulent near field compare favorably with measurements. The radiated far-field sound is predicted using the Ffowcs Williams and Hawkings (FW-H) surface integral method. Remarkable agreement of the predicted farfield sound directivity and spectra with measurements is obtained. A preliminary discussion is presented on the correlation and possible combination of multiple spectra from different grids.