A simple model for describing hydraulic conductivity in unsaturated porous media accounting for film and capillary flow
A simple model for describing hydraulic conductivity in unsaturated porous media accounting for film and capillary flow
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DOI：
10.1029/2008wr007136
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发表时间：
2008-11
影响因子：
5.4
通讯作者：
Andre Peters;W. Durner
中科院分区：
文献类型：
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作者：
Andre Peters;W. Durner
用于表征多孔介质水力传导率的常用模型依赖于仅考虑毛细管流而忽略膜流的孔束概念。实验证据表明，这些毛细管束模型可能会大大低估不饱和多孔介质中中低含水量的水流。我们提出了一种新模型，它将简单的薄膜流函数与 Mualem 的毛细管流模型相结合。这种新模型可以轻松地与任何保水功能相结合。此外，由于其数学简单，可以在现有代码中轻松有效地实现非饱和流动问题的数值求解。我们从文献中调查了一组土壤保水性和电导率数据，这些数据都达到了干燥条件，并且现有的毛细管束模型很难描述。如果该模型与适当的保留函数相结合，则可以使用新模型很好地描述这些数据。对非饱和土壤水力数据库 (UNSODA) 数据库电导率数据的调查表明，在 75% 的数据集中，新模型使用 Akaike 信息准则的修改版本实现了最佳性能。使用理查兹方程对蒸发场景进行的数值模拟表明，通过忽略薄膜流动，蒸发速率可能会被低估一个数量级以上。
The commonly used models for characterizing hydraulic conductivity of porous media rely on pore bundle concepts that account for capillary flow only and neglect film flow. Experimental evidence suggests that water flow at medium to low water contents in unsaturated porous media can be significantly underestimated by these capillary bundle models. We present a new model that combines a simple film flow function with the capillary flow model of Mualem. This new model can easily be coupled to any water retention function. Moreover, due to its mathematical simplicity, it can easily and efficiently be implemented in existing codes for the numerical solution of unsaturated flow problems. We investigated a set of soil water retention and conductivity data from the literature that all reached dry conditions and were poorly described by existing capillary bundle models. These data were well described with the new model if the model was coupled with an appropriate retention function. Investigation of conductivity data from the UNsaturated SOil hydraulic DAtabase (UNSODA) database showed that, in 75% of all data sets, the new model achieved the best performance using a modified version of Akaike's information criterion. The numeric simulation of an evaporation scenario using Richards's equation showed that by neglecting film flow, the evaporation rate may be underestimated by more than an order of magnitude.