Optimal eddy viscosity for resolvent-based models of coherent structures in turbulent jets

Response modes computed via linear resolvent analysis of a turbulent mean-flow field have been shown to qualitatively capture characteristics the observed coherent structures in both wall-bounded and free shear flows. To make such models predictive, nonlinear forcing term must be closed. Strategies do so include imposing self-consistent sets triadic interactions, proposing various source models, or through turbulence modelling. For latter, several investigators proposed using mean-field eddy viscosity acting linearly on fluctuation field. In this study, data-driven approach is taken quantitatively improve by deducing an optimal eddy-viscosity that maximizes projection dominant mode energy-optimal structure educed spectral proper orthogonal decomposition (SPOD) data from high-fidelity simulations. We use large-eddy simulation databases for round isothermal jets at subsonic, transonic, supersonic conditions show substantially improves alignment between SPOD modes, reaching over 90% those frequencies where jet exhibits low-rank response. then consider fixed model with calibration single constant, results are generally close one. particular, standard Reynolds-Averaged-Navier-Stokes (RANS) model, coefficient, provides substantial agreement three across most energetic wavenumbers frequencies.