Comparison of confined and unconfined infiltration in transparent porous media

Siemens, Greg; Peters, S. B.; Take, W. Andy

doi:10.1002/wrcr.20101

Cited by 35 publications

(25 citation statements)

References 34 publications

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“…In this sense, the GA model is similar to the Washburn-Lukas (WL) model on the level of capillary channels (see, e.g., Lunati and Or 2009;Hilpert and Glantz 2013) and both models-by solving a Cauchy problem for a nonlinear ODE-mathematically predict a finite (although, generally speaking, discontinuous) speed of front/meniscus propagation through a dry soil or empty capillary tube. As numerous experiments and field studies showed (see, e.g., Siemens et al 2013), the GA fronts propagating downward through a practically dry soil leave a "tail" of air-filled pore space at z > d in our Fig. 1.…”

Section: Pore-scale Modelsupporting

confidence: 71%

Infiltration into Two-Layered Soil: The Green–Ampt and Averyanov Models Revisited

et al. 2015

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Infiltration into a two-layered soil (continuum scale) is studied by the Green-Ampt (GA) model where the rate of infiltration (wetting front propagation) is a non-monotonic and discontinuous function of time. Both a constant ponding depth and a ponding level falling due to evaporation and infiltration are studied theoretically and in column experiments. The triads of saturated conductivity, porosity and front pressure in the two zones, as well as gravity, control vertical infiltration. Another model on the scale of a straight cylindrical capillary uses the Averyanov regime of a film flow, modified to include a front which is a quarter of a torus, rather than a spherical cap in a standard Washburn-Lukas model. The rate of front propagation is controlled by the Newtonian viscosity, tube-film sizes, surface tension, contact angle and gravity. For both scales, Cauchy problems for ODEs with respect to the front position are solved by computer algebra integration. In the field, pedon description and textural analysis of sedimentation-controlled layering are done. Of particular note is the thick cake deposited from a flash flood water pulse, which has very low permeability and can greatly inhibit infiltration. The infiltration rates measured by tension infiltrometers fluctuate, which is attributed to the mosaic and layered special distribution of hydraulic and capillary properties of the accrued sediments. Falling ponding depth laboratory experiments were conducted in four columns with a coarse substratum (sand) subjacent to a layer of thoroughly homogenized repacked dam silt. Imbibition front stopped at the interface between two texturally contrasting B Ali Al-Maktoumi A. Al-Maktoumi et al. strata and the "waiting time" of the capillary barrier breakthrough was measured, as well as further oscillations of the infiltrations rate.

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Section: Pore-scale Modelsupporting

confidence: 71%

Infiltration into Two-Layered Soil: The Green–Ampt and Averyanov Models Revisited

et al. 2015

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“…These materials are representative of angular, poorly graded sands with d 10 , d 30 , and d 60 values of 0.75, 1.16, and 1.75 mm, respectively, for the coarse gradation and 0.13, 0.27, and 0.45 mm, respectively, for the fine gradation (Peters et al, 2011). The combination of fused quartz media and an oil mixture was used by Siemens et al (2013, 2014) and Siemens and Oldroyd (2014) to investigate unsaturated moisture migration in one‐ and two‐dimensional systems as well as by Siemens et al (2015) in heat transport experiments.…”

Section: Methodsmentioning

confidence: 99%

“…The investigation of multiphase flow using transparent porous media (Iskander et al, 2015), where the indices of refraction of the solid grains and the wetting fluid are matched (Frette et al, 1992; Stöhr and Khalili, 2006; Ovdat and Berkowitz, 2006; Kong et al, 2009; Peters et al, 2011; Siemens et al, 2013, 2014; Siemens and Oldroyd, 2014; Kashuk et al, 2014; Black and Take, 2015), is an alternative optical technique. The use of transparent porous media allows relatively inexpensive measurements to be made at high spatial and temporal resolutions for greater sample depths than are possible using light reflection or transmission techniques.…”

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confidence: 99%

Quantification of Fluid Saturations in Transparent Porous Media

Sills

Mumford

Siemens

2017

Vadose Zone Journal

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Core Ideas Imaging techniques are powerful for investigating multiphase flow in porous media. Transparent porous media can be used to quantify local fluid saturations. Efficient methods to calibrate intensity–saturation relationships are required. Our new procedure uses fewer images and measurements. Predicted saturations based on calibrated images matched independent measurements. Experiments using transparent porous media, where the indices of refraction of the solid grains and the wetting fluid are matched, can be used to quantify fluid saturations from digital images. In this study, significantly more efficient calibration and validation methods for unsaturated transparent porous media were developed, which used just three images and one saturation measurement. Imbibition and drainage column experiments were used to define the pixel intensity and saturation at residual wetting fluid saturation, as well as at residual nonwetting fluid saturation in two gradations of transparent porous media used for validation. The other images were pixel intensity at 100 and 0% wetting fluid saturation. Results from the drainage and imbibition experiments on the two transparent porous media gradations showed a log‐linear saturation–pixel intensity relationship, which agreed with the validation points from this study as well as those using a previous calibration method. We expect that this new calibration procedure will allow efficient development of saturation–pixel intensity relationships for the investigation of multiphase flow using transparent porous media under a variety of conditions.

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“…Evidence of air entrapment or pore air pressure generation that could delay infiltration was not observed (Siemens et al, 2013). No specific geomorphic features were observed during infiltration indicating air release (e.g., pockmarks).…”

Section: Wettable Sand (Strong) Mixturementioning

confidence: 93%

Processes in model slopes made of mixtures of wettable and water repellent sand: Implications for the initiation of debris flows in dry slopes

Lourenço

Wang

Kamai

2015

Engineering Geology

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a b s t r a c tDebris flows in slopes initially dry, such as post-wildfire debris flows, are initiated by surface runoff and sediment bulking due to reduced infiltration. Soil water repellency, extreme dry soils, and loose, cohesionless materials influence their initiation. The exact link between these features, the resulting infiltration processes and the initiation mechanism of a debris flow remains unclear. Here, we examine the relation between soil particle wettability and slope processes in physical models. Flume experiments were conducted in 10% increments of mass ratios of wettable to water repellent sand, subjected to artificial rainfall with monitoring of soil water content, pore water pressure, sediment and water discharge and failure mode. To date, wettability was considered only for the water repellent end, because it reduces infiltration, enhancing surface runoff. This study demonstrates that slight wettability changes, in the full wettable to water repellent range, impact a variety of slope processes. The two extremes, fully wettable and water repellent gave opposite responses, retrogressive slides for infiltrationinitiated in wettable sand and erosion by surface runoff in water repellent sand. The transition was dominated by surface runoff and preferential flow, yielding a combination of erosion and slides. From the tests, a continuous capping effect generated by water repellency was a necessary condition for erosion and sand bulking i.e., the generation of runoff-initiated debris flows. The sensitivity of the model slope response to artificial rainfall was particularly acute at high ratios of wettable to water repellent sand. For mixtures above a critical ratio of wettable to water repellent sand, the measurements with an index test revealed a fully wettable material despite differences in the infiltration, saturation and pore water pressure built-up trends. Implications for post-wildfire debris flows and debris flows in slopes initially dry in general are discussed.

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Comparison of confined and unconfined infiltration in transparent porous media

Cited by 35 publications

References 34 publications

Infiltration into Two-Layered Soil: The Green–Ampt and Averyanov Models Revisited

Infiltration into Two-Layered Soil: The Green–Ampt and Averyanov Models Revisited

Quantification of Fluid Saturations in Transparent Porous Media

Processes in model slopes made of mixtures of wettable and water repellent sand: Implications for the initiation of debris flows in dry slopes

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