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

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.