Comparison of Numerical Techniques Used for Simulating Variable-Density Flow and Transport Experiments

Goswami, Rohit; Clement, T. Prabhakar; Hayworth, Joel H.

doi:10.1061/(asce)he.1943-5584.0000428

Cited by 12 publications

(7 citation statements)

References 28 publications

(45 reference statements)

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“…The wedge data shown in these figures were obtained by visually delineating the wedge location by comparing the color intensity with the reference wedges that are prepared using a salt solution colored with different dye concentration levels. In some of our previous studies we have also employed image analysis procedures to test and verify different types of interfaces (Goswami et al, ; Goswami et al, ). All the saltwater wedge experiments analyzed in this study formed extremely sharp interfaces, which can be seen in Figure data.…”

Section: Modeling Results For the Experimental Data Setmentioning

confidence: 99%

Laboratory and Numerical Investigation of Saltwater Intrusion Processes in a Circular Island Aquifer

Memari

Bedekar

Clement

2020

Water Resources Research

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A novel radial flow experimental system to study saltwater intrusion processes in an island aquifer is presented. The study investigated steady state and transient scenarios involving advancing and receding saltwater wedges in a circular island. The experimental results were simulated using the density‐coupled version of the MODFLOW‐USG code. The experimental data along with the model simulation results are employed to develop a new radial benchmark problem for testing density‐coupled models used for simulating saltwater intrusion processes. The experimental data for transient changes in toe position and freshwater storage level indicated an asymmetric pattern where the intrusion time scale is greater than the recession time scale. Numerical experiments were completed to further investigate this asymmetric effect and to intercompare the associated transient transport processes in circular and linear strip islands. We also analyzed the sensitivity of island geometry in controlling the freshwater storage levels under different recharge conditions. Modeling results show that for similar‐sized systems, circular islands are more efficient in storing freshwater than linear strip islands.

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Section: Modeling Results For the Experimental Data Setmentioning

confidence: 99%

Laboratory and Numerical Investigation of Saltwater Intrusion Processes in a Circular Island Aquifer

Memari

Bedekar

Clement

2020

Water Resources Research

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“…These transport processes have been investigated by several researchers via laboratory and/or numerical experiments e.g., [12,[14][15][16][17][18][19][20][21][22][23]. In many of these physical model studies, heavier fluids, containing salt, were placed on top of a column or tank filled with saturated porous media containing freshwater.…”

Section: Past Experimental and Numerical Studiesmentioning

confidence: 99%

“…Fingering was observed in most of these experiments either visually through photographs [12,14,15,17,18], or by some sort of digital processing [20,22]. Mulqueen et al [24] stated that the nonlinear dynamics of the unstable system made it impossible to predict where a finger would grow or how it might develop.…”

Section: Past Experimental and Numerical Studiesmentioning

confidence: 99%

Stochastic Nature of Salt Mass Transport in Porous Media Under Unstable Conditions

Mamoua¹,

Pandit²,

Heck³

2017

Hydrol Current Res

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The two main transport mechanisms that occur simultaneously under unstable flow conditions are transport of saltwater from an overlying salt source to the porous media, and transport of salt through the porous media. These mechanisms were simultaneously studied through two fixed mass experiments conducted over 15 days. The transport through the porous media was also studied via three continuous injection experiments lasting between 5 to 29 days. There was no hydraulic gradient across the porous media in any of the experiments. Experiments were conducted in a 1 cm thick plexiglass rectangular sand column (1.70 m × 0.61 m × 0.61 m). The saline source concentration was 36 g/l, and the source heights were 4.5 cm. The sand porosity and hydraulic conductivity were 32% and 9.0 m/d, respectively. The rate of mass transport from the source to the porous media was observed by measuring the salt concentration within the source, while the salt transport through the porous media was documented by measuring breakthrough curves at five locations within the sand column. Fixed mass experiment results, using mass analysis, showed that the salt transport from the source to the porous media was deterministic since both experiments produced identical rates of mass transport from the source to the porous media, the salt transport through the porous media was stochastic since the observed breakthrough curves at the five locations were considerably different. The breakthrough curves measured in three identical continuous injection experiments were also very different supporting the results of the fixed mass experiments. The implications of these findings are that, under unstable conditions, one can predict the salt mass that would enter from a salt source into the underlying porous media with certainty, one cannot predict the rate or pattern of salt transport through the porous media itself.

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“…The SEAWAT runs were solved using the total variation diminishing (TVD) scheme for advective flow with dispersivities set to zero, minimizing the width of the fresh/salt mixing zone. Compared to the finite‐difference solution scheme, TVD increases run times but reduces numerical dispersion (Goswami et al ).…”

Section: Details Of Anaqsim Swi and Seawat Comparisons Modelsmentioning

confidence: 99%

Analytic Element Modeling of Steady Interface Flow in Multilayer Aquifers Using AnAqSim

Fitts¹,

Godwin²,

Feiner³

et al. 2014

Groundwater

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This paper presents the analytic element modeling approach implemented in the software AnAqSim for simulating steady groundwater flow with a sharp fresh-salt interface in multilayer (three-dimensional) aquifer systems. Compared with numerical methods for variable-density interface modeling, this approach allows quick model construction and can yield useful guidance about the three-dimensional configuration of an interface even at a large scale. The approach employs subdomains and multiple layers as outlined by Fitts (2010) with the addition of discharge potentials for shallow interface flow (Strack 1989). The following simplifying assumptions are made: steady flow, a sharp interface between fresh- and salt water, static salt water, and no resistance to vertical flow and hydrostatic heads within each fresh water layer. A key component of this approach is a transition to a thin fixed minimum fresh water thickness mode when the fresh water thickness approaches zero. This allows the solution to converge and determine the steady interface position without a long transient simulation. The approach is checked against the widely used numerical codes SEAWAT and SWI/MODFLOW and a hypothetical application of the method to a coastal wellfield is presented.

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Comparison of Numerical Techniques Used for Simulating Variable-Density Flow and Transport Experiments

Cited by 12 publications

References 28 publications

Laboratory and Numerical Investigation of Saltwater Intrusion Processes in a Circular Island Aquifer

Laboratory and Numerical Investigation of Saltwater Intrusion Processes in a Circular Island Aquifer

Stochastic Nature of Salt Mass Transport in Porous Media Under Unstable Conditions

Analytic Element Modeling of Steady Interface Flow in Multilayer Aquifers Using AnAqSim

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