Direct Numerical Simulations of Mixing and Reaction in a Nonpremixed Homogeneous Turbulent Flow.

摘要

Direct(numerical simulations have been performed to study the mechanisms of mixing and chemical reaction in a three dimensional, homogeneous turbulent flow under the influence of the reaction of the type A + B products. The results are used to examine the applicability of Toor's hypothesis and also to determine the range of validity of various coalescence-dispersion (C/D) turbulence models that have been used previously to model the effects of turbulent mixing in such flows. The results of numerical simulations indicate that the probability density function (PDF) of a conserved Shvab-Zeldovich scalar quantity, characterizing the mixing process, evolves from an initial double-delta distribution to an asymptotic shape that can be approximated by Gaussian distribution. During this evolution, the PDF cannot be characterized by its first two moments; therefore, the application of Toor's hypothesis is not appropriate for the predictions of such flows. Molecular mixing; Coalescence-dispersion (C/D) models; Homogeneous turbulence; Direct numerical simulation. (jes)