Effect of transient solute loading on free convection in porous media

Xie, Yueqing; Simmons, Craig T.; Werner, Adrian D.; Ward, James

doi:10.1029/2010wr009314

Cited by 27 publications

(39 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since then, it has become a well‐studied typical example of natural convection phenomena both for benchmarking numerical simulators [e.g., Oldenburg and Pruess , 1995; Kolditz et al , 1998; Ackerer et al , 1999] and for serving as a base case to investigate more complicated free convection problems [e.g., Prasad and Simmons , 2003; Post and Prommer , 2007]. It was adopted by Xie et al [2010] to investigate the effect of time‐variant solute loading upon natural convection in porous media. Xie et al [2010] pointed out that the classic Elder problem is more relevant to natural salt lake settings [e.g., Van Dam et al , 2009] because of the high density of the imposed solute (1,200 kg m −3 ), equivalent to a salinity of 360,000 mg L −1 [ Adams and Bachu , 2002].…”

Section: Mathematical Modelingmentioning

confidence: 99%

“…It was adopted by Xie et al [2010] to investigate the effect of time‐variant solute loading upon natural convection in porous media. Xie et al [2010] pointed out that the classic Elder problem is more relevant to natural salt lake settings [e.g., Van Dam et al , 2009] because of the high density of the imposed solute (1,200 kg m −3 ), equivalent to a salinity of 360,000 mg L −1 [ Adams and Bachu , 2002]. In order to adjust the classic Elder problem to be more representative of natural settings, two significant modifications were made, which included replacing the thermal diffusion coefficient with solute hydrodynamic dispersion and changing the bottom concentration boundary condition to a no‐solute flux boundary condition.…”

Section: Mathematical Modelingmentioning

confidence: 99%

“…Consequently, the modified dispersive Elder problem demonstrated a large number of unstable fingers beneath the top boundary layer and is a more realistic example for solute‐driven natural convection. The reader is referred to the work by Xie et al [2010] for a detailed description of the modified dispersive Elder problem. In the current study, we adapted this dispersive Elder problem as our natural free convection base case by two slight modifications in order to weaken aquifer‐scale circulation and shorten simulation times, as discussed in the rest of this section.…”

Section: Mathematical Modelingmentioning

confidence: 99%

“…In the dispersive Elder problem, Xie et al [2010] still retained the middle half concentration boundary condition on the top from the solute analogous Elder problem [ Voss and Souza , 1987] to supply solute to the groundwater system. This boundary condition may, for example, represent a salt lake above an extensive groundwater system.…”

Section: Mathematical Modelingmentioning

confidence: 99%

See 3 more Smart Citations

Speed of free convective fingering in porous media

Xie

Simmons

Werner

2011

Water Resources Research

Self Cite

View full text Add to dashboard Cite

[1] Previous studies have examined free convection and the development of fingers in variable-density groundwater environments, but the penetration rates of fingering processes (i.e., fingering speeds) have not been systematically investigated. Unlike common groundwater processes driven by advection and whose flow rates may be computed using Darcy's law, fingering speeds are far less intuitive. In this study, fingering speeds are analyzed in a natural convection system using two measurable diagnostics: deepest plume front (DPF, providing upper bounds on plume speeds) and vertical center of solute mass (COM, providing global speeds). The permeability, porosity, and dispersion (longitudinal and transverse dispersivities) were varied using a perturbation-based stochastic approach to investigate their effects on fingering speeds. Modeling results show that the characteristic convective velocity, commonly used to represent theoretical fingering speeds, needs to incorporate effective porosity in a similar fashion to hydraulically driven average linear velocity and needs to be further adjusted by multiplying by a corrective factor f for predicting various fingering behaviors (approximately f ¼ 0.115 for DPF and f ¼ 0.034 for COM) in this study. A stochastic analysis demonstrates small variability in the time-varying speed of both DPF and COM between model realizations. This indicates that reproducing fingering speeds is likely to be achieved and that one single realization can adequately produce f for the characteristic convective velocity. This study also identifies that f for speeds of DPF is most likely to be constrained by (0.115, 1.000), which is extremely useful in the design of laboratory and field experimentation.

show abstract

Section: Mathematical Modelingmentioning

confidence: 99%

Section: Mathematical Modelingmentioning

confidence: 99%

Section: Mathematical Modelingmentioning

confidence: 99%

Section: Mathematical Modelingmentioning

confidence: 99%

See 2 more Smart Citations

Speed of free convective fingering in porous media

Xie

Simmons

Werner

2011

Water Resources Research

Self Cite

View full text Add to dashboard Cite

show abstract

“…Number of fingers (NOF) has been used by a few studies as an indicator for quantifying unstable fingering flows [Prasad and Simmons, 2003;2005;Xie et al, 2010] and it is defined by regions bounded by the salinity contour of 15.1 ppt. Figure 6.8 compares the variation of NOF for all unstable cases on the Rayleigh-Péclet plot (Figure 6.6) at different elapsed times.…”

Section: Number Of Fingersmentioning

confidence: 99%

Effects of salinity variations on subsurface flow in salt marshes

Shen¹

View full text Add to dashboard Cite

Salt marshes are important intertidal wetlands at the land-ocean interface with a wide range of ecological functions, such as providing essential habitats for intertidal fauna, affecting the productivity of coastal waters via nutrient exchange, maintaining coastal biodiversity and moderating greenhouse gas emission. However, over the past few decades the area of salt marshes worldwide has declined sharply due to human activities. To reverse such a trend, it is urgent for us to understand the various processes that underpin the ecological functions of marsh systems. Among these processes, the pore-water flow plays an important role. Many studies, including field investigations and numerical simulations, have been conducted to examine the pore-water flow in salt marshes under the influences of tidal oscillation, evapotranspiration, precipitation, soil properties, topography and inland freshwater input.However, the impacts of salinity variations have been neglected.The study in this thesis aimed to explore the effects of salinity variations, especially due to salinity differences between the surface and subsurface water, on pore-water flow in salt marshes. Laboratory experiments and numerical simulations were carried out to examine the influences of upward and downward salinity gradients on pore-water flow and associated solute transport in the marsh soil. The study also provided insights into unstable pore-water flow in the soil under variably-saturated conditions.In the investigation on the impacts of upward salinity gradient on pore-water flow in salt marshes, both laboratory experiment and numerical simulations revealed that, combined with tidal fluctuations, the upward salinity gradient modified the stability of the system, and induced unstable flow and salt fingers in the marsh soil. The size and number of salt fingers both varied from the near-creek zone to marsh interior. Near the creek the finger size was larger but there were less fingers, while in the interior area there were more fingers but of smaller sizes. This was because that a relatively strong circulation and advection near the creek overwhelmed the density effect, which became dominant as the circulation and advection weakened in marsh interior. The unstable fingers altered largely the pore-water ii flow locally and the associated solute transport, especially in the marsh interior. The results of particle tracking showed that the downward penetration of fingers led to wider and faster exchange in the marsh interior. However, the overall water exchange between marsh sediments and coastal water was only slightly enhanced as it was still largely controlled by the tidal oscillation.In the investigation on the effects of downward salinity gradient on pore-water flow in salt marshes, both laboratory experiments and numerical simulations found that, unlike the case of upward salinity gradient, the downward salinity gradient maintained the stability of the system with the plume moving steadily downward in a manner similar to that of the case wit...

show abstract

Numerical investigation of coupled density‐driven flow and hydrogeochemical processes below playas

Hamann

Post

Kohfahl

et al. 2015

Water Resources Research

Self Cite

View full text Add to dashboard Cite

Numerical modeling approaches with varying complexity were explored to investigate coupled groundwater flow and geochemical processes in saline basins. Long‐term model simulations of a playa system gain insights into the complex feedback mechanisms between density‐driven flow and the spatiotemporal patterns of precipitating evaporites and evolving brines. Using a reactive multicomponent transport model approach, the simulations reproduced, for the first time in a numerical study, the evaporite precipitation sequences frequently observed in saline basins (“bull's eyes”). Playa‐specific flow, evapoconcentration, and chemical divides were found to be the primary controls for the location of evaporites formed, and the resulting brine chemistry. Comparative simulations with the computationally far less demanding surrogate single‐species transport models showed that these were still able to replicate the major flow patterns obtained by the more complex reactive transport simulations. However, the simulated degree of salinization was clearly lower than in reactive multicomponent transport simulations. For example, in the late stages of the simulations, when the brine becomes halite‐saturated, the nonreactive simulation overestimated the solute mass by almost 20%. The simulations highlight the importance of the consideration of reactive transport processes for understanding and quantifying geochemical patterns, concentrations of individual dissolved solutes, and evaporite evolution.

show abstract

Effect of transient solute loading on free convection in porous media

Cited by 27 publications

References 36 publications

Speed of free convective fingering in porous media

Speed of free convective fingering in porous media

Effects of salinity variations on subsurface flow in salt marshes

Numerical investigation of coupled density‐driven flow and hydrogeochemical processes below playas

Contact Info

Product

Resources

About