基于等效孔隙网络模型的水动力弥散数值模拟  

Numerical simulations of hydrodynamic dispersion based on an equivalent pore network model

作　　者：张兴昊 林丹彤 胡黎明[1] ZHANG Xinghao;LIN Dantong;HU Liming(State Key Laboratory of Hydroscience and Engineering,Department of Hydraulic Engineering,Tsinghua University,Beijing 100084,China)

机构地区：[1]清华大学水利水电工程系,水沙科学与水利水电工程国家重点实验室,北京100084

出　　处：《清华大学学报（自然科学版）》2022年第12期1906-1914,共9页Journal of Tsinghua University(Science and Technology)

基　　金：国家重点研发计划(2020YFC1806502);清华大学水沙科学与水利水电工程国家重点实验室基金项目(2020-KY-01,2021-D-03)。

摘　　要：等效孔隙网络模型基于统计参数描述多孔介质中复杂的孔隙结构,常用于分析多孔介质中渗流和机械弥散等物质运移过程的微观机理,但对溶质运移过程中分子扩散作用的研究相对较少。该文基于等效孔隙网络模型研究了多孔介质中溶质的对流、分子扩散和机械弥散过程,对多孔介质中溶质的运移规律进行研究。通过对等效孔隙网络模型参数进行敏感性分析,研究了多孔介质孔隙结构特征对有效扩散系数的影响;通过对比仅考虑机械弥散与同时考虑分子扩散和机械弥散的计算结果,讨论了分子扩散对于水动力弥散过程的影响。计算结果表明:有效扩散系数受到孔隙体积与孔喉扩散能力的共同影响,与孔喉曲率负相关,与配位数和连接数比值正相关;分子扩散作用与对流导致的机械弥散过程有耦合作用,分子扩散作用加速了溶质在低流速区域的运移。该文揭示了分子扩散作用影响水动力弥散过程的微观机理,为孔隙网络模型中的溶质运移通量计算提供了理论依据。An equivalent pore network model(EPNM) describes complex pore structures in a porous media by statistical parameters. Previous studies using such models have focused on seepage and mechanical dispersion, with few studies considering the effect of molecular diffusion on solute transport. In this study, the convection, molecular diffusion and mechanical dispersion of solutes in porous media were studied using an EPNM to predict the solute transport in porous media. A sensitivity analysis of the model parameters was used to study the effect of the pore structure characteristics on the effective diffusion coefficient of the porous media. The influence of molecular diffusion on the hydrodynamic dispersion was analyzed by comparing numerical results with and without molecular diffusion. The results show that the effective diffusion coefficient, which negatively correlates with the throat curvature and positively correlates with the coordinate number and the connection number ratio, is affected by both the pore volume and the pore-throat diffusion capacity. The molecular diffusion correlates with the convection-induced mechanical dispersion to accelerate the solute transport in the low-velocity region. The results of this study show the microscopic mechanisms influencing molecular diffusion for hydrodynamic dispersion as a theoretical basis for predicting the solute transport flux in pore network models.

关 键 词：污染物运移 水动力弥散 分子扩散 多孔介质 等效孔隙网络模型 

分 类 号：TU42[建筑科学—岩土工程]