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Drainage mechanisms in porous media : From piston-like invasion to formation of corner flow networks

Hoogland, Frouke; Lehmann, Peter; Mokso, Rajmund LU and Or, Dani (2016) In Water Resources Research 52(11). p.8413-8436
Abstract

Water drainage from porous media is a highly dynamic process often marked by rapid piston-like air invasion events at the front and other rapid interfacial reconfigurations. Liquid phase entrapped behind the moving front drains at significantly slower rates often via gravity driven flow through corners and crevices. This distribution of slowly draining residual water phase determines the plant available water and biological functioning of soils. The study aims to determine the conditions for the flow regime transition from piston-like invasion at a drainage front to slower corner dominated flow at the pore and sample scale. This transition was observed experimentally for sand and glass beads with fast X-ray tomography, revealing water... (More)

Water drainage from porous media is a highly dynamic process often marked by rapid piston-like air invasion events at the front and other rapid interfacial reconfigurations. Liquid phase entrapped behind the moving front drains at significantly slower rates often via gravity driven flow through corners and crevices. This distribution of slowly draining residual water phase determines the plant available water and biological functioning of soils. The study aims to determine the conditions for the flow regime transition from piston-like invasion at a drainage front to slower corner dominated flow at the pore and sample scale. This transition was observed experimentally for sand and glass beads with fast X-ray tomography, revealing water fragmentation into clusters of full pores interconnected by water corner films. The observed liquid morphology at the transition from piston to corner flow was reproduced by a quasi-static pore network model and predicted by percolation theory. The amount of capillary-retained water at flow transition controlling the subsequent drainage dynamics could be reproduced by an idealized star shaped pore whose geometry is deduced from macroscopic properties of the porous medium. Predictions of water content thresholds at flow transitions were in agreement with other critical saturation values associated with cessation of solute diffusion and of internal drainage (at field capacity) highlighting the criticality of water phase continuity disruption for formation of relatively stable unsaturated conditions controlled by slow corner flow that support life in soil.

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author
publishing date
type
Contribution to journal
publication status
published
keywords
corner flow, drainage, pore scale, water connectivity, X-ray tomography
in
Water Resources Research
volume
52
issue
11
pages
24 pages
publisher
American Geophysical Union
external identifiers
  • scopus:84996615345
ISSN
0043-1397
DOI
10.1002/2016WR019299
language
English
LU publication?
no
id
90d35536-4622-4f57-9b29-419f9a2e8a53
date added to LUP
2017-09-19 14:36:04
date last changed
2017-11-19 04:43:05
@article{90d35536-4622-4f57-9b29-419f9a2e8a53,
  abstract     = {<p>Water drainage from porous media is a highly dynamic process often marked by rapid piston-like air invasion events at the front and other rapid interfacial reconfigurations. Liquid phase entrapped behind the moving front drains at significantly slower rates often via gravity driven flow through corners and crevices. This distribution of slowly draining residual water phase determines the plant available water and biological functioning of soils. The study aims to determine the conditions for the flow regime transition from piston-like invasion at a drainage front to slower corner dominated flow at the pore and sample scale. This transition was observed experimentally for sand and glass beads with fast X-ray tomography, revealing water fragmentation into clusters of full pores interconnected by water corner films. The observed liquid morphology at the transition from piston to corner flow was reproduced by a quasi-static pore network model and predicted by percolation theory. The amount of capillary-retained water at flow transition controlling the subsequent drainage dynamics could be reproduced by an idealized star shaped pore whose geometry is deduced from macroscopic properties of the porous medium. Predictions of water content thresholds at flow transitions were in agreement with other critical saturation values associated with cessation of solute diffusion and of internal drainage (at field capacity) highlighting the criticality of water phase continuity disruption for formation of relatively stable unsaturated conditions controlled by slow corner flow that support life in soil.</p>},
  author       = {Hoogland, Frouke and Lehmann, Peter and Mokso, Rajmund and Or, Dani},
  issn         = {0043-1397},
  keyword      = {corner flow,drainage,pore scale,water connectivity,X-ray tomography},
  language     = {eng},
  month        = {11},
  number       = {11},
  pages        = {8413--8436},
  publisher    = {American Geophysical Union},
  series       = {Water Resources Research},
  title        = {Drainage mechanisms in porous media : From piston-like invasion to formation of corner flow networks},
  url          = {http://dx.doi.org/10.1002/2016WR019299},
  volume       = {52},
  year         = {2016},
}