摘要：Infiltration is dominantly gravity driven, and a viscous-flow approach was developed. Laminar film flow equilibrates gravity with the viscous force and a constant flow velocity evolves during a period lasting 3/2 times the duration of a constant input rate, q S . Film thickness F and the specific contact area L of the film per unit soil volume are the key parameters. Sprinkler irrigation produced in situ time series of volumetric water contents, θ( z , t ), as determined with TDR probes. The wetting front velocity v and the time series of the mobile water content, w ( z , t ) were deduced from θ( z , t ). In vitro steady flow in a core of saturated soil provided volume flux density, q ( z , t ), and flow velocity, v , as determined from a heat front velocity. The F and L parameters of the in situ and the in vitro experiments were compared. The macropore-flow restriction states that, for a particular permeable medium, the specific contact area L must be independent from q S i.e., d L /d q S = 0. If true, then the relationship of q S ∝ v 3/2 could scale a wide range of input rates 0 ≤ q S ≤ saturated hydraulic conductivity, K sat , into a permeable medium, and kinematic-wave theory would become a versatile tool to deal with non-equilibrium flow. The viscous-flow approach is based on hydromechanical principles similar to Darcy’s law, but currently it is not suited to deduce flow properties from specified individual spatial structures of permeable media.
