Residual air saturation changes during consecutive drainage–imbibition cycles in an air–water fine sandy medium

Li, Yan; Flores, Giancarlo; Xu, Jun; Yue, Weizhong; Wang, Yuxin; Luan, Tiang-gang; Gu, Qingbao

doi:10.1016/j.jhydrol.2013.08.050

Cited by 12 publications

(5 citation statements)

References 51 publications

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“…The TDR and T5 tensiometer probes were calibrated following Li et al (, ). Effects of water velocity on the probes' accuracy, changes in their accuracy, and signal drifts during prolonged formal column tests were also monitored.…”

Section: Methodsmentioning

confidence: 99%

“…As shown in the illustration of the experimental apparatus in Figure , the sandy medium used in the drainage experiments was placed in 44‐cm‐long polymethyl methacrylate columns with an inner diameter of 10 cm, an upper boundary solely open to air, and lower boundary open to both air and water. The hydraulic properties were measured online using conventional instruments and techniques (Li et al, ,). An SWT5 tensiometer probe (Delta‐T Devices Ltd.) and Trime‐IT Time‐domain reflectometry (TDR) probe (IMKO, Micromodultechnik GmbH, Germany) were installed on opposite sides of each column, 22.0 cm above its bottom, to measure capillary pressure and water saturation, respectively.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Factors Influencing Dynamic Nonequilibrium Effects in Drainage Processes of an Air‐Water Two‐Phase Fine Sandy Medium

Li¹,

He²,

et al. 2019

Water Resources Research

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In efforts to reduce uncertainties about effects of minor changes in the pore structure of porous media on dynamic nonequilibrium effects (DNEs), we monitored water saturation‐capillary pressure relationships in both dynamic flow and static states in stepwise drainage processes of a sandy medium. The acquired data were used to detect DNE and their changes with time in each drainage step and construct new parameters to characterize DNE. Effects of factors affecting water flow—including capillary number, water saturation, rate of change of water saturation with time (△Sw/△t), and the maximum value of this rate (RSMAX)—on the magnitude of the DNE were then determined. Results show that entry pressures are considerably larger under dynamic flow conditions than under static flow conditions, and DNE only occurs when the water saturation exceeds a threshold value in a drainage process. During either a smooth drainage or drainage step, the maximum capillary pressure (PMAX) is reached before the minimum water saturation (SMIN). Moreover, in drainage steps RSMAX occurs before the maximum difference between the capillary pressures associated with the static and dynamic states (DPMAX), except when they start from the saturated state. Accordingly, DNEs in a drainage step are mainly reflected in the time between PMAX and SMIN (△t), DPMAX, the average sum of the squares of the difference between capillary pressures of the static and dynamic states (DPAVE), and the dynamic coefficient τ (which is often used to characterize DNE). Furthermore, our results indicate that the water saturation and its rate of change with time are more important parameters than the capillary number for modeling DNE in a drainage process, and we detected no clear correlation between either maximum or minimum values of τ and the timing of the most significant DNE during drainages. τ appears to characterize DNE effectively in smooth drainage processes, while △t, DPAVE, and DPMAX constitute meaningful supplementary parameters for the characterization of DNE in a drainage step of a stepwise drainage.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Factors Influencing Dynamic Nonequilibrium Effects in Drainage Processes of an Air‐Water Two‐Phase Fine Sandy Medium

Li¹,

He²,

et al. 2019

Water Resources Research

Self Cite

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“…The cycle of imbibition and drainage occurs repetitively in the nature system's unsaturated zone. Li et al (2013) [16] conducted a series of column experiments to study the saturation-capillary pressure relation under consecutive drainage-imbibition cycles. During consecutive imbibition-drainage cycles, the saturation of the non-wetting phase (S nw ) varied in the stable and unstable states.…”

Section: Introductionmentioning

confidence: 99%

The Displacement of the Resident Wetting Fluid by the Invading Wetting Fluid in Porous Media Using Direct Numerical Simulation

Wang

Huang

Hsu

2023

Water

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Understanding the displacement of the resident wetting fluid in porous media is crucial to the remediation strategy. When pollutants or nutrients are dissolved in the surface wetting fluid and enter the unsaturated zone, the resident wetting fluid in the porous system may remain or be easily flushed out and finally arrive in the groundwater. The fate and transport of the resident wetting fluid determine the policy priorities on soil or groundwater. In this study, the displacement of the resident wetting fluid by the invading wetting fluid in porous media was simulated using direct numerical simulation (DNS). Based on the simulations of the displacements in porous media, the effect of the non-wetting fluid on the displacement was evaluated by observation and quantification, which were difficult to achieve in laboratory experiments. The result can also explain the unknown phenomenon in previous column experiments, namely that the old water is continuously released from the unsaturated porous media even after a long period of flushing with the new water. The effects of the interfacial tension, contact angle, and injection rate, which affected the immiscible fluid–fluid flow pattern, were also evaluated. Since pollutants dissolved in the wetting fluid could change the physical properties of the wetting fluid, the interfacial tensions of the resident wetting fluid and the invading wetting fluid were set separately in the simulation. Moreover, our simulation demonstrated that the consecutive drainage–imbibition cycles could improve the displacement of the resident wetting fluid in porous media. The successful simulation in this study implied that this method can be applied to predict other immiscible fluid–fluid flow in natural or industrial processes.

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“…The amount of the entrapped non-wetting phase in porous media depends predominantly on the pore structure [8], but also on the history of wetting and drying [11,12] as well as the contact angle [5,13]. Higher values of the contact angle lead to a suppression of the snap-off mechanism, resulting in a smaller amount of entrapped air.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Capillary Trapping of Air on Satiated Hydraulic Conductivity of Sands Interpreted by X-ray Microtomography

Princ

Fideles

Koestel

et al. 2020

Water

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The relationship between entrapped air content and the corresponding hydraulic conductivity was investigated experimentally for two coarse sands. Two packed samples of 5 cm height were prepared for each sand. Air entrapment was created by repeated infiltration and drainage cycles. The value of K was determined using repetitive falling-head infiltration experiments, which were evaluated using Darcy’s law. The entrapped air content was determined gravimetrically after each infiltration run. The amount and distribution of air bubbles were quantified by micro-computed X-ray tomography (CT) for selected runs. The obtained relationship between entrapped air content and satiated hydraulic conductivity agreed well with Faybishenko’s (1995) formula. CT imaging revealed that entrapped air contents and bubbles sizes were increasing with the height of the sample. It was found that the size of the air bubbles and clusters increased with each experimental cycle. The relationship between initial and residual gas saturation was successfully fitted with a linear model. The combination of X-ray computed tomography and infiltration experiments has a large potential to explore the effects of entrapped air on water flow.

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Residual air saturation changes during consecutive drainage–imbibition cycles in an air–water fine sandy medium

Cited by 12 publications

References 51 publications

Factors Influencing Dynamic Nonequilibrium Effects in Drainage Processes of an Air‐Water Two‐Phase Fine Sandy Medium

Factors Influencing Dynamic Nonequilibrium Effects in Drainage Processes of an Air‐Water Two‐Phase Fine Sandy Medium

The Displacement of the Resident Wetting Fluid by the Invading Wetting Fluid in Porous Media Using Direct Numerical Simulation

The Impact of Capillary Trapping of Air on Satiated Hydraulic Conductivity of Sands Interpreted by X-ray Microtomography

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