Assessment of turbulent combustion submodels using the Linear Eddy Model

Linear Eddy Model (LEM) simulations are conducted in order to study turbulence-chemistry interactions in a homogeneous, incompressible, stationary turbulent flow with non-premixed reactants. The chemical kinetics model used in this work involves single- and multi-step, reversible and irreversible isothermal reactions. The simulation results are employed to investigate flame structure and statistics and comparisons are made to several other turbulent combustion models. Specifically, comparisons of the LEM results to predictions obtained from the Stationary Laminar Flamelet Model (SLFM) and the Conditional Moment Closure (CMC) method are presented. The results show qualitative trends similar to those of previous Direct Numerical Simulations (DNS) for simpler chemistry and provide insights into several key modeling assumptions. For the chemistry under consideration and within the context of comparisons to the LEM simulation results: (1) SLFM predictions agree better with the LEM results for larger values of the scalar dissipation rate, (2) the effect of neglecting conditional fluctuations on the chemical source terms in the CMC formulation is negligible, (3) CMC accurately predicts intermediate species and (4) CMC predictions are sensitive to the closure model selected for the conditional scalar dissipation.