SCALAR MIXING IN STATIONARY ISOTROPIC TURBULENCE USING MAPPING CLOSURE APPROXIMATION
(0) A probability density function (PDF) method is known as a promising method for the simulation of turbulent reacting flows due to the fact that the chemical reaction term appears in close form. However, construction of a general and accurate model for molecular mixing in transport PDF equation is still of great challenge. Recently, a mapping closure model introduced by Kraichnan and his coworkers seems to present a good attack on this problem, providing a deductive method for conditional dissipation rates and conditional diffusions. The model can produce the shape relaxation of the scalar PDF from an initial double delta distribution to a Gaussian one.Nevertheless, it is not able to provide the rate at which the scalar evolves, i.e., it is not closed in the sense that a time scale is needed. Attempts were made by He and Zhang to solve this problem by a two-point closure strategy, which was referred to as the MCA approach. In this work, to make the MCA more adaptable, a novel numerical method for the initialization of reference fields for given initial scalar fields is proposed.Furthermore, the original MCA model is extended in the sense that both the correlations and the variance of the reference fields are time-evolving, this relaxation was found to be responsible for the correct prediction of scalar variance decaying. We then simulated turbulent scalar mixing in stationary isotropic turbulence systematically using the improved MCA, taking into account the different initial scalar-to-velocity length scale ratios. The evolution of scalar PDF,decaying of scalar variance and dissipation rate of scalar mixing are found to be in good agreement with Eswaran & Popes DNS results in all length scale ratios considered.Moreover, the evolution of the mapping function was found to be approaching linear at later stage of mixing. Possible amendments for the MCA model are also discussed.
Yin-Chun Wang Guo-wei He Jian Zhang
State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Be Departmcnt of fluids machinery, School of Jet Propulsion, BeiHang University, Beijing
国际会议
昆明
英文
671-675
2006-09-18（万方平台首次上网日期，不代表论文的发表时间）