A MCA model for molecular diffusion in turbulent reactive flows
化学反应流中分子扩散的二点封闭MCA模型

In the PDF approach of turbulent reactive flows,the convection and reaction terms are closed but the molecular diffusuion term is unclosed.The currently existing models for the molecular diffusion are either empirical or introduced via external parameters,and it has been verified that they are not valid for such physical processes as the diffusion process.In this paper,a stochastically mapping approximation approach is developed to model the effect of molecular diffusion.A length scale is introduced by a two-point joint probability density function,to account for the evolutions of the conditional diffusion.Numerical simulation shows that the approach is able to predict the evolution of the variances,dissipation rates,conditional diffusion and PDFs in the diffusion process.