Effective velocity and effective dispersion coefficient for finite-sized particles flowing in a uniform fracture

James, Scott C.; Chrysikopoulos, Constantinos V.

doi:10.1016/s0021-9797(03)00254-6

Cited by 68 publications

(69 citation statements)

References 35 publications

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“…These contradictory findings are probably due to the very limited number of experimental data used, and the experimental conditions that led to significant mass retention caused by straining and/or attachment. The velocity enhancement of colloid particles, which is often observed in studies of colloid and biocolloid transport in fractures and micromodels, is commonly attributed to colloid exclusion from the lower-velocity regions [James and Chrysikopoulos, 2003;Auset and Keller, 2004]. However, in porous media, in addition to colloid exclusion from the lower-velocity regions [Scheibe and Wood, 2003], colloid particles experience a substantial reduction of the effective porosity [Morley et al, 1998], as illustrated in Figure 5.…”

Section: 1002/2014wr016094mentioning

confidence: 92%

Colloid particle size‐dependent dispersivity

Chrysikopoulos,

Katzourakis

2015

Water Resources Research

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115

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Laboratory and field studies have demonstrated that dispersion coefficients evaluated by fitting advection-dispersion transport models to nonreactive tracer breakthrough curves do not adequately describe colloid transport under the same flow field conditions. Here an extensive laboratory study was undertaken to assess whether the dispersivity, which traditionally has been considered to be a property of the porous medium, is dependent on colloid particle size and interstitial velocity. A total of 48 colloid transport experiments were performed in columns packed with glass beads under chemically unfavorable colloid attachment conditions. Nine different colloid diameters and various flow velocities were examined. The breakthrough curves were successfully simulated with a mathematical model describing colloid transport in homogeneous, water-saturated porous media. The experimental data set collected in this study demonstrated that the dispersivity is positively correlated with colloid particle size, and increases with increasing velocity. The dispersivity values determined in this laboratory study were compared with 380 dispersivity values from earlier laboratory and field-scale solute, colloid and biocolloid transport studies published in the literature.

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Section: 1002/2014wr016094mentioning

confidence: 92%

Colloid particle size‐dependent dispersivity

Chrysikopoulos,

Katzourakis

2015

Water Resources Research

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115

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“…As the aggregates of large size cannot pass through small pores, they tend to migrate through larger pores in the connected fractures. The effective particle velocity is elevated, while the overall particle dispersion is degraded in a fracture (James and Chrysikopoulos 2003); therefore, the pulse change in electrical conductivity caused by the nZVI tracer migration is faster, but less dispersive than that caused by the saline tracer.…”

Section: Discussion and Conclusion Discussionmentioning

confidence: 99%

“…The difference in velocity can be attributed to different viscosity, density and interference between the slurry and the solution. The difference in velocity and dispersivity can also be induced by elevated velocity and degraded dispersion coefficient due to larger size of nZVI particles than that of solutes (James and Chrysikopoulos 2003).…”

Section: Simulation Of the Nzvi Tracer Testmentioning

confidence: 99%

Mapping fracture flow paths with a nanoscale zero-valent iron tracer test and a flowmeter test

et al. 2017

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The detection of preferential flow paths and the characterization of their hydraulic properties are important for the development of hydrogeological conceptual models in fractured-rock aquifers. In this study, nanoscale zerovalent iron (nZVI) particles were used as tracers to characterize fracture connectivity between two boreholes in fractured rock. A magnet array was installed vertically in the observation well to attract arriving nZVI particles and identify the location of the incoming tracer. Heat-pulse flowmeter tests were conducted to delineate the permeable fractures in the two wells for the design of the tracer test. The nZVI slurry was released in the screened injection well. The arrival of the slurry in the observation well was detected by an increase in electrical conductivity, while the depth of the connected fracture was identified by the distribution of nZVI particles attracted to the magnet array. The position where the maximum weight of attracted nZVI particles was observed coincides with the depth of a permeable fracture zone delineated by the heat-pulse flowmeter. In addition, a saline tracer test produced comparable results with the nZVI tracer test. Numerical simulation was performed using MODFLOW with MT3DMS to estimate the hydraulic properties of the connected fracture zones between the two wells. The study results indicate that the nZVI particle could be a promising tracer for the characterization of flow paths in fractured rock.

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“…To calculate this factor, some empirical correlations are usually used, (James & Chrysikopoulos, 2003).…”

Section: General Definition Of the Enhancement Factormentioning

confidence: 99%

Mechanisms of Particle Transport Acceleration in Porous Media

2008

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Abstract. Experimental data show that the groundwater transport of radionuclides in porous media is frequently facilitated when accompanied with colloid particles. This is usually explained by the size exclusion mechanism which implies that the particles move through the largest pores where the flow velocity is higher.We call attention to three other mechanisms which influence the colloid particle motion, while determining both the probable transport facilitation and retardation. First of all, it is shown that the transport facilitation may be significantly reduced and even transformed into a retardation due to the growth of the effective suspension viscosity (a friction-limited facilitation). Secondly, we will show that the transport of particles through the largest pores can be retarded due to a reduced connectivity of the large-pore cluster (a percolation-breakup retardation). Thirdly, we highlight the Fermi mechanism of acceleration known in statistical physics which is based on the elastic collisions between particles. All three effects are analyzed in terms of the velocity enhancement factor, by using statistical models of porous media in the form of a capillary bundle and a 3D capillary network. Optimal and critical regimes of velocity enhancement are quantified. Estimations show that for realistic parameters, the maximal facilitation of colloid transport is close to the experimentally observed data.

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Effective velocity and effective dispersion coefficient for finite-sized particles flowing in a uniform fracture

Cited by 68 publications

References 35 publications

Colloid particle size‐dependent dispersivity

Colloid particle size‐dependent dispersivity

Mapping fracture flow paths with a nanoscale zero-valent iron tracer test and a flowmeter test

Mechanisms of Particle Transport Acceleration in Porous Media

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