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  • 1
    Language: English
    In: Soil Science Society of America Journal, 2013, Vol.77(2), pp.403-411
    Description: The influence of clay content in soil-pore structure development and the relative importance of macroporosity in governing convective fluid flow are two key challenges toward better understanding and quantifying soil ecosystem functions....
    Keywords: Life Sciences ; Agricultural Sciences ; GAS ; Models ; Consequences ; Porosity ; Air Permeability ; Parameters ; Transport ; Microtomography ; Quantification ; Agriculture
    ISSN: 0361-5995
    E-ISSN: 1435-0661
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  • 2
    Language: English
    In: Advances in Water Resources, September 2016, Vol.95, pp.288-301
    Description: Biofilm growth changes many physical properties of porous media such as porosity, permeability and mass transport parameters. The growth depends on various environmental conditions, and in particular, on flow rates. Modeling the evolution of such properties is difficult both at the porescale where the phase morphology can be distinguished, as well as during upscaling to the corescale effective properties. Experimental data on biofilm growth is also limited because its collection can interfere with the growth, while imaging itself presents challenges. In this paper we combine insight from imaging, experiments, and numerical simulations and visualization. The experimental dataset is based on glass beads domain inoculated by biomass which is subjected to various flow conditions promoting the growth of biomass and the appearance of a biofilm phase. The domain is imaged and the imaging data is used directly by a computational model for flow and transport. The results of the computational flow model are upscaled to produce conductivities which compare well with the experimentally obtained hydraulic properties of the medium. The flow model is also coupled to a newly developed biomass–nutrient growth model, and the model reproduces morphologies qualitatively similar to those observed in the experiment.
    Keywords: Porescale Modeling ; Imaging Porous Media ; Microtomography ; Biomass and Biofilm Growth ; Parabolic Variational Inequality ; Multicomponent Multiphase Flow and Transport in Porous Media ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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  • 3
    Language: English
    In: Geoderma, January 2015, Vol.237-238, pp.9-20
    Description: Soil macropores largely control fluid and solute transport, making visualization and quantification of macropore characteristics essential for better understanding and predicting soil hydrogeochemical functions. In this study, seventeen large (19 × 20 cm) intact soil cores taken across a loamy field site (Silstrup, Denmark) were scanned at in-situ sampling conditions (~ field capacity) at a relatively coarse resolution (500 μm) by medical X-ray computed tomography (CT). In the image analyses, artifacts related to the presence of rocks were identified and removed before linking CT-derived pore parameters to measured fluid transport parameters. After CT scanning, soil cores were saturated and drained at − 20 hPa soil–water potential, leaving only pores 〉 150 μm air-filled. Air permeability (k ) and air-filled porosity (ε ) were measured to evaluate gas transport behavior in macropore networks under these conditions. Finally, tracer transport experiments at a constant, high flow rate (10 mm h ) were carried out, and the arrival time for 5% of the applied tracer (T ) was used as an index for the magnitude of water transport in macropores. Although X-ray CT scanning only identified 5–25% of the total air-filled pore network at − 20 hPa, CT-derived macroporosity (average for whole column) and macroporosity for the limiting-quarter section of each column were highly correlated to both k and T (R from 0.6 to 0.8). The CT-inferred limiting depth for soil–gas transport was typically located at 90–165 mm depth, and likely a result of soil management history. Results suggest that the functional macropore network for fluid transport was well quantified by rapid, coarse-resolution X-ray CT scanning. Linking rapid X-ray CT scanning with classical fluid transport measurements on large intact columns thus proves highly useful for characterizing soil macropore functions and in perspective may prove to be useful in predicting field-scale variations in gas, water, and chemical transport.
    Keywords: Macropores ; Limiting-Section Macroporosity ; X-Ray Computed Tomography ; Air Permeability ; 5% Tracer Arrival Time ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 4
    In: Water Resources Research, August 2010, Vol.46(8), pp.n/a-n/a
    Description: In this work, the constitutive relationship between capillary pressure (), saturation (), and fluid‐fluid interfacial area per volume (IFA) is characterized using computed microtomography for drainage and imbibition experiments consisting of a nonaqueous phase liquid and water. The experimentally measured relationship was compared to a thermodynamic model that relates the area under the − curve to the total IFA, , and the capillary‐associated IFA, . Surfaces were fit to the experimental and modeled − − and − − data in order to characterize the relationship in three dimensions (3D). For the experimental system, it was shown that the − − relationship does not exhibit hysteresis. The model is found to provide a reasonable approximation of the magnitude of the 3D surfaces for and , with a mean absolute percent error of 26% and 15%, respectively. The relatively high mean absolute percent errors are primarily the result of discrepancies observed at the wetting‐ and nonwetting‐phase residual saturation values. Differences in the shapes of the surfaces are noted, particularly in the curvature (arising from the addition of scanning curves and presence of − hysteresis in the predicted results) and endpoints (particularly the inherent nature of thermodynamic models to predict significant associated with residual nonwetting‐phase saturation). Overall, the thermodynamic model is shown to be a practical, inexpensive tool for predicting the − − and − − surfaces from − data.
    Keywords: Multiphase Flow ; Capillary Pressure ; Saturation ; Interfacial Area ; Microtomography ; Thermodynamic
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 5
    Language: English
    In: Vadose Zone Journal, 01 November 2011, Vol.10(4)
    Description: Engineered capillary barriers typically consist of two layers of granular materials designed so that the contrast in material hydraulic properties and sloping interface retains infiltrating water in the upper layer. We report here on the results of two bench-top capillary barrier experiments, interpretation, and numerical modeling. We measured hydraulic parameters for two coarse materials using standard methods and found that the materials had similar hydraulic properties despite being morphologically different (round vs. angular). The round sand provided a better functioning capillary barrier than the angular sand, but neither experiment could be characterized as a perfectly working capillary barrier. In both cases, more than 93% of the infiltrating water was successfully diverted from the lower layer, however, infiltration into the underlying layer was observed in both systems. Based on this work, we believe that non-continuum processes such as vapor diffusion and film flow contribute to the observed phenomena and are important aspects to consider with respect to capillary barrier design, as well as dry vadose zone processes in general. Using a theoretical film flow equation that incorporates the surface geometry of the porous material we found that infiltration into the coarse underlying sand layer appeared to be dominated by water film flow. The NUFT (Non-isothermal Unsaturated-saturated Flow and Transport) model was used for qualitative comparison simulations. We were able to reproduce the barrier breach observed in the experiments using targeted parameter adjustment, by which pseudo-film flow was successfully simulated.
    Keywords: Materials Science ; Engineering ; Design ; Diffusion ; Film Flow ; Geometry ; Granular Materials ; Hydraulics ; Performance ; Porous Materials ; Sand ; Simulation ; Transport ; Water ; Water Film, Vadose Zone, Capillary Barrier ; Agriculture ; Engineering
    ISSN: 1539-1663
    E-ISSN: 1539-1663
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  • 6
    Language: English
    Description: Report covers the background for the workshop, objectives, important research directions, necessary capabilities and overall recommendations.
    Keywords: Pore Structure ; Fluid Flow ; Biogeochemistry ; Transport ; Solutes ; Absorption ; 37 Inorganic, Organic, Physical And Analytical Chemistry ; Porosity ; Simulation ; Scale Models ; Colloids ; Recommendations ; Geochemistry ; Nuclear Magnetic Resonance ; Tomography ; Fabrication ; Substrates ; Engineers ; Permeability ; Precipitation
    Source: University of North Texas
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  • 7
    Language: English
    Description: Report covers the background for the workshop, objectives, important research directions, necessary capabilities and overall recommendations.
    Keywords: Inorganic, Organic, Physical And Analytical Chemistry ; Absorption ; Biogeochemistry ; Colloids ; Engineers ; Fabrication ; Fluid Flow ; Geochemistry ; Nuclear Magnetic Resonance ; Permeability ; Pore Structure ; Porosity ; Precipitation ; Recommendations ; Scale Models ; Simulation ; Solutes ; Substrates ; Tomography ; Transport
    Source: SciTech Connect (U.S. Dept. of Energy - Office of Scientific and Technical Information)
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