View Video Presentation: https://doi.org/10.2514/6.2022-0460.vid

Coherent structures in the far-field of a round turbulent jet are investigated experimentally and modeled by linear stability analysis (LSA) and resolvent analysis (RA) which are based on the linearized operator of the incompressible Navier-Stokes equations. The linearized operator is complemented with a constant eddy viscosity with the goal of mimicking a part of the turbulent interactions. A parametric study is conducted to investigate the influence of eddy viscosity on the modeling success in terms of alignment between modeled and empirical SPOD modes. The optimal eddy viscosity corresponds to a frequency-independent value that is derived by self-similar scaling laws and a fit to the Boussinesq equation based on the experimental data. With this value, excellent agreement between empirical and modeled structures is found in almost the entire resolved frequency range and for all investigated azimuthal wavenumbers ranging from m=0 to m=5. A budget of the spectral turbulent kinetic energy equation is derived for the jet far field to assess the influence of eddy viscosity on the budget of turbulent production, dissipation and nonlinear transfer. Within this context, the nonlinear transfer can be decomposed into a term that constitutes an energy sink which is introduced by the eddy dissipation and a remaining nonlinear term that is positive and acts as a source. Both terms are found to dominate the budget and strongly exceed turbulent production at medium to high frequencies.