Flow of water in porous media with saturation overshoot: A review

•Saturation overshoot can take place in porous media during both imbibition and redistribution processes.•Experimental conditions for the occurrence of overshoot generally coincide with those of gravity-driven fingered flow.•Capillary pressure overshoot is usually accompanied by saturation over-shoo...

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Bibliographic Details
Published in:Journal of hydrology (Amsterdam) 2014-03, Vol.510, p.353-362
Main Author: Xiong, Yunwu
Format: Article
Language:English
Subjects:
Capillary pressure
Earth sciences
Earth, ocean, space
Exact sciences and technology
Fingered flow
Hydrogeology
Hydrology
Hydrology. Hydrogeology
Mathematical analysis
Mathematical models
Media
Moisture content
Pressure overshoot
Saturation
Saturation overshoot
Soil water content
Unsaturated
Wetting
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Summary:•Saturation overshoot can take place in porous media during both imbibition and redistribution processes.•Experimental conditions for the occurrence of overshoot generally coincide with those of gravity-driven fingered flow.•Capillary pressure overshoot is usually accompanied by saturation over-shoot.•Theoretical models to account for saturation overshoot are reviewed and assessed. Different from classic wetting patterns, saturation overshoot (also called saturation-bump or non-monotonic saturation profile) is widely observed in unsaturated porous media. Saturation overshoot is the case of a high and uniform water content zone directly behind the wetting front followed by another region with a low and uniform saturation. This paper reviews recent research progress on this anomalous phenomenon, focusing on experimental observations and theoretical model development. Experimental conditions for the occurrence of overshoot generally coincide with those of gravity-driven fingered flow. Saturation overshoot is associated with the corresponding capillary pressure overshoot. The Richards equation in its basic form cannot describe the non-monotonic saturation field due to its parabolic nature and incompleteness in physics. Several attempts to modify the Richards equation and other approaches proposed recently have been reviewed and assessed. The knowledge gaps and research opportunities on saturation overshoot are summarized at the end.
ISSN:0022-1694
1879-2707
DOI:10.1016/j.jhydrol.2013.12.043