中文摘要：

垃圾填埋场滤出液、入侵海水、核废物及生产生活废水等污染物随地下水的迁移威胁人类生存。地下水渗流的随机性导致溶质运移问题更加复杂。根据流网特点，利用流线与水头等势线对求解域进行离散，基于质量守恒原理建立流网单元内溶质浓度求解的隐式有限体积差分格式。基于多孔介质孔隙流速分布规律，利用蒙特卡洛法建立流管单元随机流速场进行溶质运移过程的数值模拟，最后根据数值模拟和模型试验的结果对比，验证了数值模拟方法的准确性。基于流网单元的数值模型中沿流线方向的物质交换由对流和扩散共同作用，而流管间的物质交换只有扩散作用，因此，可在不使用弥散系数下进行污染物运移的模拟。引入随机方法确定流管内流速为研究非均匀流场中染污物的优势迁移提供了新的思路。

英文摘要：

The contaminants, such as filtrate of waste landfill, intrusion seawater, nuclear waste, production sewage and living sewage, would threaten human survival when they migrate into groundwater system. Randomness of groundwater seepage makes the problem of solute transport more complicated. According to the characteristics of flow net, implicit difference scheme of the solution of unit solute concentration based on the principle of mass conservation with the stream tube element is solved by the streamline and equipotential lines. Based on the velocity distribution patterns of porous media, the Monte Carlo method is used to establish the flow rate field for simulating the process of migration of solute. The accuracy of the numerical simulation method is proved by the comparison of the simulation and model tests. In the numerical model the convection and diffusion have effect on the substance exchange along the direction of stream tube. However, only solute diffusion exists between stream tubes. In this model, the feasibility of dispersion coefficient and the limitation of feasibility are overcome. The method for determining flow rate with randomness can provide a new idea for research of advantage migration of contaminants in heterogeneous flow field.