A pore-scale model for simulating water flow in unsaturated soil

A - Papers appearing in refereed journals

Hu, W., Guofeng, L. and Zhang, X. 2018. A pore-scale model for simulating water flow in unsaturated soil . Microfluidics and Nanofluidics. 22 (7), p. 22:71. https://doi.org/10.1007/s10404-018-2090-0

AuthorsHu, W., Guofeng, L. and Zhang, X.

Pore-scale simulation and tomography have been used in a combination over the past decade to study some fundamental physical and biogeochemical processes in soil that are difficult or impossible to measure, one of which is water flow in unsaturated soil. Considering that an important application of pore-scale simulation in soil is to elucidate how convective water flow distributes soluble nutrients through the heterogeneous pore space when water flow is in steady state, we propose an alternative model in this paper to simulate unsaturated water flow at pore scale. The model is quasi-static, consisting of two steps. The first one is to determine water distribution in the pore geometry using a morphological model; once the water distribution is known under a pressure, the water-air interface is fixed in space. The second step is to simulate water flow numerically by solving the Stokes equations in which the water-air interface is treated as a boundary. We test the water flow model against analytical solution of thin water film flow over a non-slip solid wall, and then combine it with the morphological model to simulate water flow in 3D soil structures acquired using X-ray tomography at resolution of 10 A mu m. As a validation, we compare the permeability calculated by the model under different saturations with those estimated by the van Genuchten formula using the saturated permeability and water retention parameters obtained from the morphological model. We also discuss the pros and cons of the model and its implications in unsaturated soil modelling.

KeywordsPore-scale modelling; Unsaturated soil; Water flow; Water-air interface; X-ray tomography; Stokes equations
Year of Publication2018
JournalMicrofluidics and Nanofluidics
Journal citation22 (7), p. 22:71
Digital Object Identifier (DOI)https://doi.org/10.1007/s10404-018-2090-0
Open accessPublished as non-open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeS2N - Soil to Nutrition - Work package 1 (WP1) - Optimising nutrient flows and pools in the soil-plant-biota system
Output statusPublished
Publication dates
Online16 Jun 2018
Publication process dates
Accepted09 Jun 2018
PublisherSpringer Heidelberg
Copyright licensePublisher copyright

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