A Study on the Turbulent Diffusion of Matter and Small Particles by the Random Fourier Modes Method and Stochastic Model

该项目已按初步研究计划实施。本文的研究进展和结果概括如下：（A）三维均匀湍流中物体周围羽流扩散场的数值模拟（1）首先，我们研究了在网格湍流中发展的点源羽流扩散场（无物体情况）。用随机傅立叶模方法和双粒子随机模型进行了数值模拟。两种模型的模拟结果与实验结果吻合较好。(2)采用随机傅立叶模态法和快速畸变理论相结合的方法，模拟了物体周围的湍流场。利用该模拟湍流场，考察了垂直于圆柱面的点源羽流的特性，并利用探针模拟了网格湍流中的反应混合层 ...更多信息 能力密度函数（PDF）方法。目的（B）快速畸变理论模拟复杂湍流的运动学方法的发展及其在扩散场模拟中的应用主要是对均匀湍流剪切流和轴对称收缩/膨胀流的快速畸变理论的解析解进行了综述。结果表明，在轴对称收缩/膨胀流的情况下，存在时间稳定解，而在均匀湍流剪切流的情况下，存在时间不稳定解。利用直接数值模拟（DNS）得到的颗粒的拉格朗日轨迹，估计了均匀各向同性湍流中的涨落标量统计。少

This project has been put through according to the initial research plan. The progress and results of the research are summarized in the following,Object (A) Simulation of plume diffusion field around the body in the three dimensional turbulent flow with a uniform mean velocity(l) At first, we investigated the plume diffusion field from a point source developed in the grid-turbulence (in case of no body). The numerical simulations have been made by the random Fourier modes method and a Two-particle stochastic model. The simulation results obtained by both models show good agreements with the experimental results.(2) The turbulent field around the body has been simulated by combining the random Fourier modes method and the rapid distortion theory. By using this simulated turbulent field, the characteristics of a point source plume running perpendicularly into the cylinder have been examined.Furthermore, the reactive mixing layer in the grid-turbulence has been also simulated by the prob … More ability density function (pdf) method. From this time on, an application of this pdf method to the diffusion around the cylinder has been tried.Object (B) Development of kinematic method to simulate the complex turbulent flows by the rapid distortion theory, ant its application to the simulation of diffusion fieldsMainly, the analytical solutions of the rapid distortion theory for the homogeneous turbulent shear flows and axisymmetric contraction/expansion flows have been surveyed. Consequently, it was found that in cases of the axisymmetric contraction/expansion flows there exist the temporally stable solutions, but the solution for the homogeneous turbulent shear flows are temporally unstable.Besides the initial research plan, the diffusion fields of matter in the turbulent pipe flow has been investigated. Further, the fluctuation scalar statistics in the homogeneous isotropic turbulence were estimated from the Lagrangian trajectories of material particles obtained by the direct numerical simulation (DNS). Less