Mixed convection processes below a saline disposal basin

Simmons, Craig T.; Narayan, Kumar A.

doi:10.1016/s0022-1694(96)03204-0

Cited by 89 publications

(87 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…When the density-dependent flow is involved, salt marshes are subject to mixed convection (free and forced convection). According to the work of Simmons and Narayan [1997], besides the Rayleigh number, the P eclet number should also be considered under the scenario of mixed convection to identify the onset condition of unstable flow.…”

Section: Discussionmentioning

confidence: 99%

Effects of salinity variations on pore water flow in salt marshes

Shen

Jin

Xin

et al. 2015

Water Resources Research

View full text Add to dashboard Cite

Spatial and temporal salinity variations in surface water and pore water commonly exist in salt marshes under the combined influence of tidal inundation, precipitation, evapotranspiration, and inland freshwater input. Laboratory experiments and numerical simulations were conducted to investigate how density gradients associated with salinity variations affect pore water flow in the salt marsh system. The results showed that upward salinity (density) gradients could lead to flow instability and the formation of salt fingers. These fingers, varying in size with the distance from the creek, modified significantly the pore water flow field, especially in the marsh interior. While the flow instability enhanced local salt transport and mixing considerably, the net effect was small, causing only a slight increase in the overall mass exchange across the marsh surface. In contrast, downward salinity gradients exerted less influence on the pore water flow in the marsh soil and slightly weakened the surface water and groundwater exchange across the marsh surface. Numerical simulations revealed similar density effects on pore water flow at the field scale under realistic conditions. These findings have important implications for studies of marsh soil conditions concerning plant growth as well as nutrient exchange between the marsh and coastal marine system.

show abstract

Section: Discussionmentioning

confidence: 99%

Effects of salinity variations on pore water flow in salt marshes

Shen

Jin

Xin

et al. 2015

Water Resources Research

View full text Add to dashboard Cite

show abstract

“…Several studies have focused on CO 2 density-driven convection in homogeneous porous media and its relevant applications (Simmons and Narayan 1997;Hassanzadeh et al 2005Hassanzadeh et al , 2007Farajzadeh et al 2007;Lu and Lichtner 2007;Kandaswamy and Eswaramurthi 2008;Pau et al 2010; Musuuza et al 2011). Typical approaches for creating instability convection rely on applying initial perturbations to trigger the developments of fingerings for dissolved CO 2 .…”

Section: Introductionmentioning

confidence: 99%

Effects of Permeability Variations on CO2 Convection in Anisotropic and Heterogeneous Saline Formations

Lin¹,

Lee³

et al. 2016

Terr. Atmos. Ocean. Sci.

View full text Add to dashboard Cite

This study simulated the natural convection of dissolved carbon dioxide (CO 2 ) in a small-scale heterogeneous saline formation using the state module ECO2N equation in the TOUGHREACT model. A one-way downscaling approach that involves using a series of sub-models in simulation procedures was proposed to efficiently simulate problems with high-scale discrepancies. This study evaluated the effects of different degrees of small-scale permeability variations on the vertical migration of dissolved CO 2 . The sequential Gaussian simulation model was used to generate unconditional random permeability fields for different natural logarithm of permeability (lnk) variations (i.e., lnk variances and correlations in x and z directions). The results showed an identical transition zone of dissolved CO 2 near the top boundary, where a constant CO 2 gas saturation was specified. The local permeability variations can trigger fingerings and enhance the vertical convection of the dissolved CO 2 . The number of fingerings depends on the variations in permeability near the front interface of the dissolved CO 2 (i.e., the bottom edge of the transition zone for the dissolved CO 2 ). However, the fingering patterns and developments are constrained by the permeability variations along the fingering paths. At the same mean lnk permeability the convection fluxes increase with an increase in lnk variances. However, an increase in lateral correlations (i.e., increase in the correlation lengths in the x direction) can slightly reduce the convection fluxes at the same lnk variance. The highly variable flux rates of the dissolved CO 2 occur early and the variations in the flux rate decrease with time.

show abstract

“…For example, this is fairly common at landfills and waste dump sites [1][2][3], saline disposal basins [4], seawater inundation along coastal aquifers [5], and in estuaries [6][7][8][9][10][11]. Typically, when saltwater and freshwater are in contact with each other, the groundwater flow is due to natural hydraulic gradients, and the movement of the fluid is termed "forced" convection.…”

Section: Forced Free and Mixed Convective Flowmentioning

confidence: 99%

“…Some of the key findings regarding the transport of salt through the porous media are: 1) under free convection conditions, saltwater moves through the porous media in the form of lobe shaped fingers, and convective dispersion, as opposed to molecular and mechanical dispersion, is the key transport mechanism [12,15,20], 2) the number and configuration of these fingers were not reproducible in practical experiments [12,15], 3) fingering causes rapid and erratic redistribution of solutes [15], and the salt travels faster and farther when fingers are formed as opposed to when the transport is due to mechanical dispersion [15,17], 4) salt plumes move faster and farther with increasing source concentrations [4,15], 5) fingers tend to coalesce as they move greater distances [14,16,17], and 6) not only does the salt move faster and farther once it enters the porous media, the total mass of the salt transported during free convection is typically far greater than transported by diffusion [23]. 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].…”

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

View full text Add to dashboard Cite

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.

show abstract

Mixed convection processes below a saline disposal basin

Cited by 89 publications

References 20 publications

Effects of salinity variations on pore water flow in salt marshes

Effects of salinity variations on pore water flow in salt marshes

Effects of Permeability Variations on CO2 Convection in Anisotropic and Heterogeneous Saline Formations

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

Contact Info

Product

Resources

About