非饱和带水分运动模型的Picard解法及参数灵敏度分析

Picard Solution of Moisture Movement Model in Unsaturated Zone and Parameter Sensitivity Analysis

为研究非饱和带土壤水分运动,对Richard方程的有限元求解方法进行了改进,改进后的算法可较为简便地处理边界条件,并与已有的求解方法进行对比验证;对V-G模型中的参数α和n对土壤重力释水和入渗过程的影响进行了敏感度分析。结果表明:根据本文所提出的数值方法所求解出的结果与已有的结果具有较好的一致性,且具有更高的精度;α值较小的土壤不利于重力释水的进行,但是有利于水分的入渗;n值较小的土壤不利于重力释水的进行,对于入渗过程需要具体考虑入渗源处及初始压力水头的大小。

In order to study the moisture movement in unsaturated zone, a improved finite element numerical method for solving Richard equation is built and compared with the results in presented literature. The improved numerical method can be applied easily for boundary condition. The sensitive analysis of gravity drainage and infiltration processes were carried out by varying the parameters in V--G model. The results shown that the results in this article and in the literatures were matched well and had more precision. The soil with lower value of a was characterized less gravity drainage, but the infiltration process could be happened easier. The lower parameter of n has the same effect with less gravity drainage, and in the infiltration process the pressure head in infiltration source and initial condition should be considered.