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Moving Multi-Front (MMF): A generalized Green-Ampt approach for vertical unsaturated flows

Alastal, Khalil and Ababou, Rachid Moving Multi-Front (MMF): A generalized Green-Ampt approach for vertical unsaturated flows. (2019) Journal of Hydrology, 579. 124184. ISSN 0022-1694

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Official URL: https://doi.org/10.1016/j.jhydrol.2019.124184

Abstract

A Moving Multi-Front (MMF) method is developed and tested for solving the Richards equation governing unsaturated flow in vertical homogeneous porous columns. The MMF model is a gridless method. It can be viewed as a generalization of the Green-Ampt piston flow approach, which models flow as a single abrupt moving front separating saturated and dry regions during infiltration. The MMF model further generalizes this concept, using a parametrization of unsaturated water retention and conductivity-pressure curves. It reduces the Richards PDE to an ODE system governing “M” moving front positions. Different tests are developed to validate this approach for 1D transient downwards/upwards flows submitted to constant and time-varying pressure boundary conditions. They include: (i) infiltration to deep water tables; (ii) infiltration to shallow water tables; (iii) capillary rise from fixed water tables; (iv) gradual water table rise (partially saturated column with evolving pressure condition at bottom). The MMF results are compared favorably to finely discretized fixed grid solutions of Richards PDE. Analyses of error and accuracy show satisfactory results in terms of water content profiles and boundary fluxes (e.g. infiltration rate).

Item Type:Article
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
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Deposited On:21 Jul 2021 08:25

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