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Viscosity—The weak link between Darcy's law and Richards' capillary flow
Author(s) -
Germann Peter F.
Publication year - 2018
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.11450
Subject(s) - laminar flow , capillary action , hele shaw flow , flow (mathematics) , mechanics , infiltration (hvac) , open channel flow , isothermal flow , stokes flow , viscosity , darcy's law , geology , geotechnical engineering , porous medium , thermodynamics , porosity , physics
Preferential flow, a term that includes macropore flow, non‐equilibrium flow, and finger flow, stands in well known conflict with Richards' ([Richards, L. A., 1931]) capillary flow. Acoustic velocity experiments demonstrate that preferential flow moves independently from, faster than, and before capillary flow during gravity‐driven infiltration. Viscous flow in permeable media is briefly introduced to the point where Richards' ([Richards, L. A., 1931]) particular treatment of viscosity turns out as the hydro‐mechanical bifurcation from general laminar flow. Preferential flow is expected during significant infiltration, however, spatio‐temporarily limited according to the viscous‐flow regime. Two ways of delineating capillary flow from viscous flow reveal minimum path widths of preferential flow in the range of about 20 μm.