Mixing Models for the Simulation of Stratified Combustion

摘要: RANS simulations of turbulent stratified premixed flames are performed using a presumed pdf approach. Three different models for the mean dissipation rate of the reacting scalar have been employed;(i) the classical model utilising the turbulent timescale,(ii) a model derived for premixed flames and adapted to stratified conditions and (iii) a model derived specifically for stratified flames. Simulations of two different test cases show that model (i) performs poorly; models (ii) and (iii) give acceptable agreement with experimental data. Model (ii) includes the effect of dilatation and its influence on turbulence and thus its performances are improved over model (iii). Increasing the stratification level appears to have no effect on the relative performance of the models.