Experimental study of solute dispersion in macroscopic suspension flow

Roht, Yanina Lucrecia; Boschan, Alejandro; Ippolito, I.; Chertcoff, R.

doi:10.1016/j.jconhyd.2012.11.003

Cited by 5 publications

(18 citation statements)

References 29 publications

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“…In this context, particle diffusivities in all directions result of O(10 -1 ) or smaller. In comparison, Roht et al 7 of O(10 3 ), that decreased almost 10% in the presence of the particles for Us > Uc, being the decrease of O(10 2 ). Under the strong assumption that particle random diffusive motion, characterized by a given particle dimensionless diffusivity (i.e.…”

Section: Discussionmentioning

confidence: 81%

“…Regarding the latter, recently Roht et al 7 have observed a decrease of the dispersivity of the solute in the presence of particles, for flow between parallel-plates at low Reynolds number. It is frequently considered that the diffusive random motion 6,8 exhibited by the particles, due to the long-range hydrodynamic interactions among them, is a source of dispersion enhancement for the solute, with the particles acting as mixers.…”

Section: Introductionmentioning

confidence: 98%

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Suspension flow: do particles act as mixers?

2015

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Recently, Roht et al. [J. Contam. Hydrol., 2013, 145, 10-16] observed that the presence of suspended non-Brownian macroscopic particles decreased the dispersivity of a passive solute, for a pressure-driven flow in a narrow parallel-plate channel at low Reynolds numbers. This result contradicts the idea that the streamline distortion caused by the random diffusive motion of the particles increases the dispersion and mixing of the solute. Therefore, to estimate the influence of this motion on the dispersivity of the solute, and investigate the origin of the reported decrease, we experimentally studied the probability density function (pdf) of the particle velocities, and spatio-temporal correlations, in the same experimental configuration. We observed that, as the mean suspension velocity exceeds a critical value, the pdf of the streamwise velocity of the particles markedly changes from a symmetric distribution to an asymmetric one strongly skewed to high velocities and with a peak of the most probable velocity close to the maximum velocity. The latter observations and the analysis of the suspension microstructure indicate that the observed decrease in the dispersivity of the solute is due to particle migration to the mid-plane of the channel, and consequent flattening of the velocity profile. Moreover, we estimated the contribution of particle diffusive motion to the solute dispersivity to be three orders of magnitude smaller than the reported decrease, and thus negligible. Solute dispersion is then much more affected by how particles modify the flow velocity profile across the channel than by their random diffusive motion.

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Section: Discussionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 98%

Suspension flow: do particles act as mixers?

2015

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“…Two narrow mylar strips provided a constant separation between the two plates and sealed the longest sides of the cell (see These experiments were performed at mean flow velocities ranging between 0.040 and 0.051 cm/s (leading to 350 < Pe s < 450). The range of flow velocities (of P e s ) and value of φ bulk studied in this experiments were chosen in view of the results of Roht et al [15], that observed a variation in the dispersion coefficient of the solute due to the presence of the particles only for P e s > 300 and φ > 0. 15 In addition to the displacement experiments with suspensions, a reference experiment and a light calibration, using exactly the same device assembly, were also performed.…”

Section: Experimental Device and Proceduresmentioning

confidence: 99%

“…The time variation c(x, y, t) for each point (x, y) in a measurement zone in the cell was fitted by the solution of the ADE equation to finally obtain a longitudinal Taylor dispersion coefficient D as detailed in references [28] and [15]. Both D and the dispersivity l d = D/U provide a quantitative measure of the degree of spreading of the mixing front between coloured and transparent suspension and then of the dispersion of the solute.…”

Section: Image Processing and Data Analysismentioning

confidence: 99%

“…In a previous work, Roht et al [15] measured the longitudinal dispersion coefficient D of a passive solute in the Poiseuille, parallel-plates, flow of a macroscopic suspension, for a range of particle bulk volume fractions (φ bulk ) and flow rates (quantified by the solute Péclet number P e s ). They found a decrease of D for φ bulk > 0.15 and P e s > 300 compared to φ bulk = 0, implying that the presence of the particles may reduce the dispersion of the solute in this flow configuration.…”

Section: Introductionmentioning

confidence: 99%

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Light transmission measurement of solute dispersion in non-Brownian suspension flow

Boschan

Poblete

Roht

et al. 2014

Eur. Phys. J. Appl. Phys.

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We characterize and employ a light transmission technique to measure the dispersivity of a solute in the flow of a neutrally-buoyant non-Brownian spherical particle suspension in a Hele-Shaw cell (parallelplate axial flow). Particle radii (a) were 20 and 40 μm, the particle bulk volume fraction φ bulk was 0.2, and the cell aperture was 420 ± 10 μm. In each displacement experiment a suspension with a colouring solute displaces a transparent one at constant flow rates ranging from 0.721 to 0.928 mL/min (corresponding to solute Péclet numbers (P e s) between 350 and 450). A reference measurement, identical to the displacement ones but without particles in the flow (φ bulk = 0), were performed in the same experimental assembly for comparison purposes. A light calibration related the transmitted intensity I to the solute concentration c for each combination of φ bulk and a. The time variation of the solute concentration was found to be well-fitted by the solution of the advection-dispersion equation (ADE) in the range of P es studied, and consequently a dispersion coefficient D and a dispersivity l d of the solute were measured.

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