Modeling the Response of a Forced Turbulent Premixed Flame Using Resolvent Analysis

Abstract We seek to understand the heat release response to harmonic velocity disturbance forcing using a resolvent analysis (RA) framework in this study. The flow configuration analysed in this paper is a turbulent premixed methane-air round jet flame at an equivalence ratio of 0.8 and unburnt gas temperature of 800.0 K. We study this flame in two configurations: unforced and forced. A momentum forcing term, localised within the burner tube, is used to impose harmonic axial velocity oscillations upstream of the flame at different forcing frequencies. Time resolved flow dynamics are computed using the explicit filtering large eddy simulation (EFLES) method for all the cases analyzed in this study. Resolvent analysis is used to determine input/output mode pairs that capture forcing distributions and response modes that optimally represent the flame’s heat release response. The response to the forcing imposed in the LES is determined using the optimal input/output modes. Good predictions of flame transfer function gain and phase as determined from LES are obtained from resolvent analysis, at conditions where the impact of nonlinear kinematic mechanisms causing burning area amplitude saturation are small.