Resolvent analysis of a Mach 1.5 jet for noise source identification*

Acoustic sources for an isothermal Mach 1.5 round jet are determined through resolvent analysis and spectral proper orthogonal decomposition (SPOD). Both physics-based resolvent analysis and data-driven SPOD (using a high-fidelity, experimentally-verified, large-eddy simulation (LES) database) provide a basis for predicting the perturbation field. Singular value decomposition of the resolvent operator constructed using an LES baseflow identifies optimal volumetric forcing modes and their corresponding linear responses. In order to determine physically relevant modes, projections of the highest gain responses and highest energy SPOD modes from LES realizations are computed. To determine the occurrence of the associated resolvent forcings, projections are then computed upon the full LES nonlinear terms and the distribution of these values leveraged for jet noise modeling.