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Fluid flow in porous media using image based modelling to parametrise Richards’ equation

Fluid flow in porous media using image based modelling to parametrise Richards’ equation
Fluid flow in porous media using image based modelling to parametrise Richards’ equation
The parameters in Richards’ equation are usually calculated from experimentally measured values of the soil water characteristic curve and saturated hydraulic conductivity. The complex pore structures that often occur in porous media complicate such parametrisation due to hysteresis between wetting and drying and the effects of tortuosity. Rather than estimate the parameters in Richards’ equation from these indirect measurements, image based modelling is used to investigate the relationship between the pore structure and the parameters. A three dimensional, X-ray computed tomography image stack of a soil sample with voxel resolution of 6 m has been used to create a computational mesh. The Cahn-Hilliard-Stokes equations for two fluid flow, in this case water and air, were applied to this mesh and solved using the finite element method in COMSOL Multiphysics. The upscaled parameters in Richards’ equation are then obtained via homogenisation. The effect on the soil-water retention curve due to three different contact angles, 0, 20 and 60, was also investigated. The results show that the pore structure affects the properties of the flow on the large scale and different contact angles can change the parameters for Richards’ equation.
Image based modelling, porous media, Richards’ equation
1364-5021
1-20
Cooper, Laura
b8f4b942-cb87-4386-ab29-17bdd0f53ec1
Daly, Keith
29920932-1779-4d08-81f8-bdd898191e5a
Hallett, P.D.
b027edfe-728c-4d09-bbbd-4061e6373ef6
Naveed, Muhammad
ffa04925-7d0a-42fa-b95b-548fe3e4e2db
Koebernick, Nicolai
118c4e45-02d8-42da-84c8-8ee4fac140ad
Bengough, Anthony G.
ac1f754e-002c-44f6-8907-8771a4cd1fd3
George, T.S.
a506ae83-5218-40c6-b582-7243465df9fa
Roose, Tiina
3581ab5b-71e1-4897-8d88-59f13f3bccfe
Cooper, Laura
b8f4b942-cb87-4386-ab29-17bdd0f53ec1
Daly, Keith
29920932-1779-4d08-81f8-bdd898191e5a
Hallett, P.D.
b027edfe-728c-4d09-bbbd-4061e6373ef6
Naveed, Muhammad
ffa04925-7d0a-42fa-b95b-548fe3e4e2db
Koebernick, Nicolai
118c4e45-02d8-42da-84c8-8ee4fac140ad
Bengough, Anthony G.
ac1f754e-002c-44f6-8907-8771a4cd1fd3
George, T.S.
a506ae83-5218-40c6-b582-7243465df9fa
Roose, Tiina
3581ab5b-71e1-4897-8d88-59f13f3bccfe

Cooper, Laura, Daly, Keith, Hallett, P.D., Naveed, Muhammad, Koebernick, Nicolai, Bengough, Anthony G., George, T.S. and Roose, Tiina (2017) Fluid flow in porous media using image based modelling to parametrise Richards’ equation. Proceedings of the Royal Society A, 1-20. (doi:10.1098/rspa.2017.0178).

Record type: Article

Abstract

The parameters in Richards’ equation are usually calculated from experimentally measured values of the soil water characteristic curve and saturated hydraulic conductivity. The complex pore structures that often occur in porous media complicate such parametrisation due to hysteresis between wetting and drying and the effects of tortuosity. Rather than estimate the parameters in Richards’ equation from these indirect measurements, image based modelling is used to investigate the relationship between the pore structure and the parameters. A three dimensional, X-ray computed tomography image stack of a soil sample with voxel resolution of 6 m has been used to create a computational mesh. The Cahn-Hilliard-Stokes equations for two fluid flow, in this case water and air, were applied to this mesh and solved using the finite element method in COMSOL Multiphysics. The upscaled parameters in Richards’ equation are then obtained via homogenisation. The effect on the soil-water retention curve due to three different contact angles, 0, 20 and 60, was also investigated. The results show that the pore structure affects the properties of the flow on the large scale and different contact angles can change the parameters for Richards’ equation.

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More information

Accepted/In Press date: 20 October 2017
e-pub ahead of print date: 22 November 2017
Keywords: Image based modelling, porous media, Richards’ equation

Identifiers

Local EPrints ID: 415076
URI: http://eprints.soton.ac.uk/id/eprint/415076
ISSN: 1364-5021
PURE UUID: ef2acf30-46f7-4ad4-ae6a-0ef8769b8d1a
ORCID for Laura Cooper: ORCID iD orcid.org/0000-0003-0198-7591
ORCID for Tiina Roose: ORCID iD orcid.org/0000-0001-8710-1063

Catalogue record

Date deposited: 25 Oct 2017 16:30
Last modified: 07 Oct 2020 01:55

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