非饱和流节点间导水率估计及达西平均分析

Estimations of interblock conductivity and darcian means in unsaturated flow

摘要: 针对由Gardner-Russo函数描述的特征土壤,在双饱和度坐标系中,探讨了常规节点间导水率估计与量纲一水平达西平均(k^*_H)和量纲一垂直达西平均(k^*_V)的差异.k^*_H是相邻两节点饱和度的函数,而k^*_V也是空间步长(Δx)和特征参数(α)的函数.对水平非饱和流,算术平均高估导水率,而几何与调和平均低估导水率;从相对误差空间分布看,几何平均优于算术和调和平均.对垂直非饱和流,随Δx(或α)的增大,常规估计的相对误差空间顺(或逆)时针旋转并缩小,从而降低模型准确性.k^*_H等值线具有对称性,而k^*_V不具对称性;仅当Δx或α足够小时,k^*_H才趋近于k^*_V.因此,为提高非饱和流数值模拟的准确性,必须采用精确的达西平均来计算节点间导水率.

Abstract: For the soils described by the Gardner-Russo retention function,the differences between standard estimations of interblock conductivity and the dimensionless horizontal Darcian means(k^*_H are symmetrical but those of k^*_H approaches k^*_V only when both △x and are small enough Therefore,it is rather essential to adopt Darcian means instead of the standard estimation of the unsaturated flow simulation.