Quantitative Analysis of Flow Processes in a Sand Using Synchrotron‐Based X‐ray Microtomography

By D. Wildenschild, J. Hopmans, Mark Rivers, Adam J.R. Kent. Vadose Zone Journal, 2005

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Pore‐scale multiphase flow experiments were developed to nondestructively visualize water flow in a sample of porous material using X‐ray microtomography. The samples were exposed to similar boundary conditions as in a previous investigation, which examined the effect of initial flow rate on observed dynamic effects in the measured capillary pressure–saturation curves; a significantly higher residual saturation and higher capillary pressures were found when the sample was drained fast using a high air‐phase pressure. Prior work applying the X‐ray microtomography technique to pore‐scale multiphase flow problems has been of a mostly qualitative nature and no experiments have been presented in the existing literature where a truly quantitative approach to investigating the multiphase flow process has been taken, including a thorough image‐processing scheme. The tomographic images presented here show, both by qualitative comparison and quantitative analysis in the form of a nearest neighbor analysis, that the dynamic effects seen in previous experiments are likely due to the fast and preferential drainage of large pores in the sample. Once a continuous drained path has been established through the sample, further drainage of the remaining pores, which have been disconnected from the main flowing water continuum, is prevented.

Subfields: Environmental Engineering, Mechanical Engineering, Ocean Engineering

View Paper: https://www.semanticscholar.org/paper/79ca7ac35996790ecceb696abf8a764513f04dbc

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Citations in the corpus

Imaging and image processing in porous media research (2008, methodology): “used a method based on a combination of C-means and a segmented image of the dry sample to segment images of the wet samples [59].”
Image processing of multiphase images obtained via X‐ray microtomography: A review (2014, methodology): “, 2012] or in a wet and dry state [Culligan et al., 2004; Wildenschild et al., 2005] are not discussed here.”
Image analysis algorithms for estimating porous media multiphase flow variables from computed microtomography data: a validation study (2010, methodology): “present a detailed description of the image analysis algorithms employed in current and previous investigations by [15, 16, 54], including recent improvements that affect the resulting estimates and (2) to validate these algorithms by comparing phase distribution and interfacial area estimates for a”
Representative elementary volume estimation for porosity, moisture saturation, and air‐water interfacial areas in unsaturated porous media: Data quality implications (2011, background): “The few studies comparing REV across multiple system variables in natural media have been qualitative in nature [Baveye et al., 2002; Wildenschild et al., 2005].”
Interfacial area measurements for unsaturated flow through a porous medium (2004, methodology): “…imaging [e.g., Johns and Gladden, 1999, 2000, 2001], and X-ray computerized microtomography [e.g., Auzerais et al., 1996; Coles et al., 1998; Wildenschild et al., 2002, 2005; D. Wildenschild et al., Image processing of grey-scale x-ray tomographic data using cluster analysis– based…”