Turbulent Reynolds number dependence of flame surface density transport in the context of Reynolds averaged Navier–Stokes simulations

Abstract

The influence of turbulent Reynolds number Ret on the statistical behaviour and modelling of flame surface density (FSD) transport has been analysed using a direct numerical simulation (DNS) database of freely propagating turbulent premixed flames with values of Ret ranging from 20 to 100. The variation of Ret is brought about by modifying the Damköhler and Karlovitz numbers independently of each other. The findings indicate that the qualitative behaviour of the various terms of the FSD transport equation remains unaffected by the changes in turbulent Reynolds number, but their relative contributions to the transport of FSD are affected to some extent. The effects of turbulent Reynolds number on the modelling of the turbulent transport term, the tangential strain rate term and the combined propagation and curvature terms are addressed in detail. It is demonstrated that model parameters for the turbulent transport and tangential strain rate term exhibit turbulent Reynolds number dependence for small values of Ret and assume asymptotic values for Ret⩾50. By contrast, the model parameters for the combined propagation and curvature term are found to be insensitive to the variation of turbulent Reynolds number. Existing models for the turbulent transport term and the tangential strain rate term are modified to account for the observed turbulent Reynolds number dependence.