Effects of Turbulent Reynolds Number on Turbulent Scalar Flux Modeling in Premixed Flames Using Reynolds-Averaged Navier–Stokes Simulations.

The influence of turbulent Reynolds number (Ret) on the statistical behavior and modeling of turbulent scalar flux (TSF) has been analyzed using a direct numerical simulation database of freely propagating turbulent premixed flames. A range of different values of Retis considered in which the Damköhler and Karlovitz numbers are modified independent of each other to bring about the variation of Ret. It has been found that the qualitative behavior of the various terms of the TSF transport equation does not change by the variation of Ret, but their relative contributions to the transport of TSF are affected to some extent. The effects of Reton the modeling of the TSF using both algebraic and transport equation-based closures are addressed in detail. It is demonstrated that model parameters for an existing algebraic model, and the models for turbulent transport, pressure gradient and the reaction rate terms in the TSF transport equation, all exhibit Retdependence for small values of Retbut all assume asymptotic values for Ret ≥ 50. By contrast, the model parameters for the combined molecular diffusion term are found to be insensitive to the variation of turbulent Ret. Existing models for algebraic and transport equation-based closures of TSF have been modified to account for the observed Retdependence. [ABSTRACT FROM AUTHOR]