Experimental analysis of pore-scale flow and transport in porous media

A novel, non-intrusive fluorescence imaging technique has been used to quantitatively measure the pore geometry, fluid velocity, and solute concentration within a saturated, three-dimensional porous medium. Discrete numerical averages of these quantities have been made over a representative volume o...

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Bibliographic Details
Published in:Advances in water resources 1996, Vol.19 (3), p.163-180
Main Authors: Rashidi, M., Peurrung, L., Tompson, A.F.B., Kulp, T.J.
Format: Article
Language:English
Subjects:
3D imaging
Earth sciences
Earth, ocean, space
Exact sciences and technology
fluorescence
fluorescent tracers
groundwater flow
Hydrogeology
hydrology
Hydrology. Hydrogeology
image analysis
macropore flow
microscopic measurement
physical models
plastic beads
plastics
pore-scale flow
pores
porous media
refractive index-matching
simulation
soil pore system
soil water movement
transport
velocimetry
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Summary:A novel, non-intrusive fluorescence imaging technique has been used to quantitatively measure the pore geometry, fluid velocity, and solute concentration within a saturated, three-dimensional porous medium. Discrete numerical averages of these quantities have been made over a representative volume of the medium and used to estimate macroscopic quantities that appear in conventional continuum models of flow and transport. The approach is meant to illustrate how microscopic information can be measured, averaged, and used to characterize medium-scale processes that are typically approximated constitutively. The experimental system consisted of a clear, cylindrical column packed with clear spherical beads and a refractive index-matched fluid seeded with fluorescent tracer particles and solute dye. By illuminating the fluid within the column with a scanning planar laser beam, details of flow and concentration within the pore spaces can be quantitatively observed, allowing for three-dimensional, dimensional, time dependent information to be obtained at good resolution. In time dependent information to be obtained at good resolution. In the current experiment, volumetrically averaged velocities and void-to-volume ratios are first compared with bulk measurements of fluid flux and medium porosity. Microscopic measurements of concentration are then used to construct cross-sectionally averaged profiles, mean breakthrough curves, and direct measurements of the dispersive flux, velocity variance, and concentration variance. In turn, the dispersive flux measurements are compared with mean concentration gradients to provide a basis for confirming the Fickian dispersion model and estimating dispersion coefficients for the medium. Coefficients determined in this manner are compared with others based upon traditional length-scale arguments, mean breakthrough analyses, and curve fits with numerical simulations.
ISSN:0309-1708
1872-9657
DOI:10.1016/0309-1708(95)00048-8