Improving prediction of hydraulic conductivity by constraining capillary bundle models to a maximum pore size
Improving prediction of hydraulic conductivity by constraining capillary bundle models to a maximum pore size
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DOI：
10.1016/j.advwatres.2015.09.005
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发表时间：
2015-11
影响因子：
4.7
通讯作者：
S. Iden;A. Peters;W. Durner
中科院分区：
文献类型：
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作者：
S. Iden;A. Peters;W. Durner
利用孔隙束模型由土壤水分特征曲线预测非饱和导水率是一种经济有效且应用广泛的方法。从具有连续导数的保留函数（即连续水容量函数）预测传导率的一个问题是，如果孔径分布较宽，则水力传导率曲线在接近水饱和度时表现出急剧下降。到目前为止，通过在毛细血管饱和度函数中引入显式的空气进入值，已经忽略或消除了该伪影。然而，这种校正导致保持函数不是连续可微的。我们提出了一种新的参数化的水力特性，它使用原来的饱和度函数（例如，货车van Schchten），并引入了最大孔隙半径仅在孔束模型。与使用显式空气入口的模型相比，所得到的电导率函数是平滑的，并且在接近饱和时单调增加。该模型的概念可以很容易地应用于任何组合的保留曲线和孔束模型。我们推导出封闭形式的表达式为单峰和多峰货车van Schchten-Mualem模型和应用模型的概念曲线拟合和逆建模的瞬态流出实验。由于新模型保留了滞留模型的光滑性和连续可微性，并消除了接近饱和时电导率的急剧下降，因此所得到的水力学函数在物理上更加合理，适用于理查兹方程或多相流模型的数值模拟。
The prediction of unsaturated hydraulic conductivity from the soil water retention curve by pore-bundle models is a cost-effective and widely applied technique. One problem for conductivity predictions from retention functions with continuous derivatives, i.e. continuous water capacity functions, is that the hydraulic conductivity curve exhibits a sharp drop close to water saturation if the pore-size distribution is wide. So far this artifact has been ignored or removed by introducing an explicit air-entry value into the capillary saturation function. However, this correction leads to a retention function which is not continuously differentiable. We present a new parameterization of the hydraulic properties which uses the original saturation function (e.g. of van Genuchten) and introduces a maximum pore radius only in the pore-bundle model. In contrast to models using an explicit air entry, the resulting conductivity function is smooth and increases monotonically close to saturation. The model concept can easily be applied to any combination of retention curve and pore-bundle model. We derive closed-form expressions for the unimodal and multimodal van Genuchten–Mualem models and apply the model concept to curve fitting and inverse modeling of a transient outflow experiment. Since the new model retains the smoothness and continuous differentiability of the retention model and eliminates the sharp drop in conductivity close to saturation, the resulting hydraulic functions are physically more reasonable and ideal for numerical simulations with the Richards equation or multiphase flow models.