Reacting Unsteady Reynolds-Averaged Navier–Stokes with the Tabulated Premixed Conditional Moment Closure Method

The tabulated premixed conditional moment closure model has shown the capability to model turbulent, premixed methane flames with detailed chemistry and reasonable run times in a Reynolds-averaged Navier-Stokes formulation. The tabulated premixed conditional moment closure model is a table lookup combustion model that tabulates species, reaction rates, and thermodynamic data for use by the computational-fluid-dynamics code during run time. In this work, the tabulated premixed conditional moment closure model is extended to unsteady Reynolds-averaged Navier-Stokes. The new model is validated against particle image velocimetry and laser Raman measurements of an enclosed turbulent reacting methane jet from the German Aerospace Center. The flame's reaction progress variable, its variance, and the scalar dissipation rate are calculated by the computational fluid dynamics in three dimensions. These three parameters are used to index detailed species information from the table for use by the computational-fluid-dynamics code. The scalar dissipation is used to account for the effects of the small-scale mixing, whereas a presumed shape beta function probability density function is used to account for the effects of large-scale turbulence on the reaction rates. Velocity, temperature, and major species are compared to the experimental data. Accurate predictions of the velocity fields were obtained, but accurate predictions of scalar quantities were limited by the adiabatic assumption of the tabulated premixed conditional moment closure model.