非均质土柱中溶质迁移的连续时间随机游走模拟  

Modeling solute transport in heterogeneous soil column using continuous time random walk

作　　者：熊云武[1] 黄冠华[1] 黄权中[1] 

机构地区：[1]中国农业大学水利与土木工程学院,北京100083

出　　处：《水科学进展》2006年第6期797-802,共6页Advances in Water Science

基　　金：国家自然科学基金资助项目(504790115033903050279025);教育部新世纪优秀人才支持计划(NCET-05-0125)~~

摘　　要：非均质介质中溶质迁移往往出现非费克现象,传统的对流弥散方程(ADE)则难以较好地描述这种现象。采用连续时间的随机游走理论(CTRW)研究1 250 cm长一维非均质土柱中溶质运移问题,探讨CTRW模型中参数及非费克迁移的变化特征。研究结果表明,β值的大小与介质的非均质特征有关,非均质性越强,β值越小,但β值具有相对的稳定性,然而ADE的弥散系数则具有随尺度增大而增大的现象。对于介质非均质性较强和非费克现象较明显的溶质穿透曲线,尤其是在拖尾部分,与ADE相比,CTRW具有较高的模拟精度。Solute transport in heterogeneous media always occurs in the non-Fickian process with early arrival and long-tail. We analyze the data of the breakthrough curves （BTCs） measured in a 1 250 cm long heterogeneous soil column with the continuous time random walk （CTRW） and the advection-dispersion equation （ADE）. It is found that Fickian behavior occurs in the transport at the distances from the inlet to 100 cm with a β value larger than 2, which is attributable to relatively homogeneous packing. Within the distances from 200 cm to 700 cm, the transport has significant non-Fickian behavior with β= 0.915 ± 0.024, this is due to the highly heterogeneity when packing the column. While the moderate non-Fickian transport is found within the distances from 800 cm to 1200cm, and the β value is 1.19 ± 0.069. Compared with the dispersion coefficient of ADE, β value is relative stable. Better simulation results are also obtained especially for the tails of BTCs by using CTRW with respect to ADE. It implies that CTRW is a useful method to describe the scale-dependent transport and non-Fickian transport.

关 键 词：非均质介质 连续时间随机游走 非费克现象 溶质运移 

分 类 号：P641.2[天文地球—地质矿产勘探]