Theory for Source‐Responsive and Free‐Surface Film Modeling of Unsaturated Flow
Theory for Source‐Responsive and Free‐Surface Film Modeling of Unsaturated Flow
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DOI：
10.2136/vzj2009.0085
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发表时间：
2010-05
影响因子：
2.8
通讯作者：
J. Nimmo
中科院分区：
文献类型：
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作者：
J. Nimmo
一个新的模型明确纳入了快速反应的可能性，跨越显着的距离，大量的水输入。它适用于不具有固有扩散性或不通过一系列平衡状态进行的非饱和流动过程。术语源响应用于表示流量对输入水源处的变化条件敏感地响应（例如，降雨、灌溉或积水渗透）。优先流的区域可以被概念化为自由表面膜中的层流，其沿着孔壁。这些膜可以被认为具有均匀的厚度，如现场证据所示，当由连续和充足的供水产生时，优先流以近似均匀的速率移动。每单位体积的有效表面面积定量地表征介质相对于源响应流的特性。取决于介质内条件的流强度因子表示在给定时间和位置的源响应流的量。层流理论提供了流动的源响应膜的速度和厚度的关系。结合达西-白金汉定律和连续性方程，导出了通量和动态含水量的表达式。在优先流有时或总是显着的，源响应和扩散流的相互作用的组合有可能改善预测的非饱和区通量响应水力输入和土壤水分的不断变化的分布。这种方法是有效的和物理上合理的例子包括：（i）暴雨引起的深水水位的快速波动和（ii）空间和时间依赖的土壤含水量对大孔土壤渗透的响应。
A new model explicitly incorporates the possibility of rapid response, across significant distance, to substantial water input. It is useful for unsaturated flow processes that are not inherently diffusive, or that do not progress through a series of equilibrium states. The term source‐responsive is used to mean that flow responds sensitively to changing conditions at the source of water input (e.g., rainfall, irrigation, or ponded infiltration). The domain of preferential flow can be conceptualized as laminar flow in free‐surface films along the walls of pores. These films may be considered to have uniform thickness, as suggested by field evidence that preferential flow moves at an approximately uniform rate when generated by a continuous and ample water supply. An effective facial area per unit volume quantitatively characterizes the medium with respect to source‐responsive flow. A flow‐intensity factor dependent on conditions within the medium represents the amount of source‐responsive flow at a given time and position. Laminar flow theory provides relations for the velocity and thickness of flowing source‐responsive films. Combination with the Darcy–Buckingham law and the continuity equation leads to expressions for both fluxes and dynamic water contents. Where preferential flow is sometimes or always significant, the interactive combination of source‐responsive and diffuse flow has the potential to improve prediction of unsaturated‐zone fluxes in response to hydraulic inputs and the evolving distribution of soil moisture. Examples for which this approach is efficient and physically plausible include (i) rainstorm‐generated rapid fluctuations of a deep water table and (ii) space‐ and time‐dependent soil water content response to infiltration in a macroporous soil.