Modeling of Entropy Generation in Turbulent Premixed Flames for Reynolds Averaged Navier–Stokes Simulations: A Direct Numerical Simulation Analysis

Abstract

The modeling of the mean entropy generation rate S·"' gen¯ due to combined actions of viscous dissipation, irreversible chemical reaction, thermal conduction and mass diffusion (i.e., T¯1,T¯2,T¯3, and T¯4) in the context of Reynolds averaged Navier–Stokes (RANS) simulations has been analyzed in detail based on a direct numerical simulation (DNS) database with a range of different values of heat release parameter τ, global Lewis number Le, and turbulent Reynolds number Ret spanning both the corrugated flamelets (CF) and thin reaction zones (TRZ) regimes of premixed turbulent combustion. It has been found that the entropy generation due to viscous dissipation T¯1 remains negligible in comparison to the other mechanisms of entropy generation (i.e., T¯2,T¯3, and T¯4) within the flame for all cases considered here. A detailed scaling analysis has been used to explain the relative contributions of , and T¯4 on the overall volumetric entropy generation rate S·"' gen¯ in turbulent premixed flames. This scaling analysis is further utilized to propose models for T¯1,T¯2,T¯3, and T¯4 in the context of RANS simulations. It has been demonstrated that the new proposed models satisfactorily predict T¯1,T¯2,T¯3, and T¯4 for all cases considered here. The accuracies of the models for T¯1,T¯2,T¯3, and T¯4 have been demonstrated to be closely linked to the modeling of dissipation rate of turbulent kinetic energy and scalar dissipation rates (SDRs) in turbulent premixed flames.