Noise simulations of supersonic hot jets for chevron nozzles

This paper describes a methodology combining advanced CFD technologies and the acoustic analogy for the simulation of jet noise from chevron nozzle geometries with engi- neering accuracy and eficiency. A multiblock structured mesh topology is used to represent complex nozzle geometries, including the faceted inner contours, nite nozzle thickness and chevrons. The impact of chevrons on the near-eld noise sources and far-eld noise ra- diation is simulated using the Immersed Boundary Method to overcome the dificulties in grid generation. A modied block interface condition is used for the complex multi- block mesh topology to avoid the centerline singularity. A non-matching block interface condition is developed to allow the grids to be greatly rened around the chevrons for a higher accuracy of simulation without signicantly increasing the mesh size. To enable eficient calculations, a dual time-stepping approach is used in addition to parallel compu- tation. The sub-iterations in the ctitious time are accelerated using both multigrid and implicit residual smoothing. A modied version of the Detached Eddy Simulation (DES) approach is used. Noise predictions are made with the permeable surface Ffowcs Williams and Hawkings (FWH) solution. Noise predictions are presented for chevron nozzles and baseline nozzles at the same operating conditions. A good agreement of the predicted noise spectra is found to reach St ≈ 3:0. Encouragingly, the frequencies and amplitudes of the broadband shock-associated noise are captured precisely. Details of the statistical proper- ties in the jet shear layer are presented. These include the mean ow and the turbulence intensities, the two-point space-time correlations and associated length and time scales and convection velocities for both baseline and chevron nozzles.