剪切弥散过渡过程的综合研究

The initial transition stage in the shearing dispersion process is of fundamental importance for various research fields including ecological and environmental studies. Based on the applicant’s extensive experiences from extensive studies in environmental modeling, the present project is proposed to study the initial effect dominated Taylor dispersion process under typical flow conditions. The specific objectives of this study are (1) to establish an integrated experimental facility based on the Particle Image Velocimetry (PIV) and Planer Laser Induced Fluorescence (PLIF) techniques, and to conduct high-precision dynamic experimental measurements; (2) to develop a computational program for high precision large eddy simulation (LES), and to carry out massive numerical simulation based on high precision finite difference schemes and subgrid turbulence models; (3) to extend C.C. Mei’s homogenization technique for the multi-scale perturbation analysis, and to determine the detailed concentration distribution and characteristics of the evolution. This study tries to explore the mechanism for scalar transport process by integrating experimental measurement, numerical simulation and analytical exploration, and to eventually provide scientific basis and technical support for relevant applications.

剪切弥散过渡过程对生态环境尤其是环境水利等前沿领域至关重要。本项目针对经典泰勒剪切弥散过程（圆管和槽道流动中标量弥散过程）的起始过渡阶段，（1）基于高精度粒子图像测速（PIV）与平面激光诱导荧光测量（PLIF）技术，建造标量弥散输运过程实验台架，进行高分辨率动态实验观测；（2）基于高精度差分格式与亚格子湍流模式，开发大涡模拟并行计算程序，进行大规模数值模拟；（3）拓展梅强中均质化方法，建立多尺度摄动理论分析框架，确定断面浓度分布细节及其演化特征。本课题综合运用实验观测、数值模拟和理论分析手段，探讨标量弥散输运过程起始阶段的多尺度渐近演化规律，可为相关应用提供科学依据和技术支持。

剪切弥散过渡过程的机理对于颗粒物PM2.5的捕获、环境风险评估和污水处理等环境保护领域至关重要。本项目依照国家自然科学基金项目计划书中的研究计划，综合运用理论分析、数值模拟和实验观测，对典型剪切流动（圆管和槽道流）中标量物质弥散的过渡阶段，进行了细致深入的研究工作。基于高精度粒子图像测速仪（PIV）与平面激光诱导荧光测量（PLIF）技术，建造了槽道流动中物质弥散输运过程实验台架，进行了高分辨率动态实验观测；基于高精度差分格式与亚格子湍流模式，开发大涡模拟并行计算程序，进行了大规模数值模拟；通过拓展Aris浓度矩、Aris矩与Gill弥散模型耦合方法，Chatwin长时间浓度矩展开法等，推导了典型流动中溶质的零阶至四阶浓度矩，进而得到了弥散过渡阶段浓度分布的解析解；并进一步探讨了具有界面吸收条件、风效应、污染物的释放方式（点源与线源）、填充介质条件及槽道截面比等因素对溶质弥散过程的影响。在理论分析、数值模拟和精密实验的支撑下，确定了典型剪切流动中物质弥散过渡阶段的浓度分布特征及其时空演化规律，可切实应用于颗粒物捕获装置设计、水生态环境风险评价、湿地污水处理流程优化等诸多方面，为相关应用提供了科学依据和技术支撑。