ABSTRACT Preferential flow covers macropore flow, nonequilibrium flow, and finger flow that are here exclusively approached with gravity-driven viscous flow. The basic unit is a water content wave whose two parameters are the wave's film thickness and its mainly vertical contact area per unit soil volume. The spatiotemporal wave properties depend on soil structure and on the intensity and duration of water input to the surface. Kinematic wave theory provides the mathematical tool for solving the analytical expressions. Three cases are the basic building blocks for approaching preferential flow: (a) single pulse, (b) a faster pulse trails a slower pulse, and (c) a faster pulse overtakes a slower pulse. Analytical procedures are presented for each case, and the potential of their applications is discussed. The analytical expressions and the superfluous representative elementary volume greatly facilitate preferential flow modeling.

中文翻译：

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优先流中的流体力学和运动学

摘要 优先流包括大孔流、非平衡流和指状流，这里专门用重力驱动的粘性流来处理。基本单位是含水量波，其两个参数是波的膜厚和单位土壤体积的主要垂直接触面积。时空波特性取决于土壤结构以及输入到地表的水的强度和持续时间。运动波理论为求解解析表达式提供了数学工具。三种情况是接近优先流的基本构建块：(a) 单脉冲，(b) 较快的脉冲落后于较慢的脉冲，以及 (c) 较快的脉冲超过较慢的脉冲。介绍了每个案例的分析程序，并讨论了它们的应用潜力。