Modelling of multispecies reactive transport on pore-space images

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Title: Modelling of multispecies reactive transport on pore-space images
Authors: Oliveira, TDS
Blunt, MJ
Bijeljic, B
Item Type: Journal Article
Abstract: We present a new model, named poreReact, to simulate multispecies reactive transport on pore space images. We solve the Navier–Stokes equations and the advection-diffusion equation for concentration on an unstructured grid using the finite volume method implemented in OpenFOAM. We couple it with the chemical model Reaktoro, which we use to calculate the chemical equilibrium of homogeneous reactions in each grid cell, considered as a completely mixed batch reactor. We validate the model against analytical solutions and experimental data, and investigate, for a range of Péclet numbers, the interplay between transport and reaction for multispecies reactive transport in a 3D bead pack where two streams of reactants at different pH are injected in parallel. We analyse the distribution of species and the rates of formation and consumption in the pore space and find that, despite the relative homogeneity of the bead pack and symmetry in injection conditions, the concentration fields of the products can be asymmetric because of the interplay between transport and chemical equilibrium. For different Péclet numbers, we calculate relative yields (the ratio between the observed change in concentration and the change that would be obtained if the reactants were completely mixed). We observe that lower Péclet numbers give rise to higher relative yields because of increased transverse mixing by diffusion. However, higher absolute yields are obtained at higher injection velocities because of the larger amount of matter available for reaction in a given time. Reaction is more favoured in the faster-flowing regions of the pore space. However, this effect is more marked for species for which advection is the dominant mechanism of transport to reactive sites, as opposed to diffusion-mediated reactions where the full velocity distribution is sampled before reaction occurs.
Issue Date: 1-May-2019
Date of Acceptance: 17-Mar-2019
ISSN: 0309-1708
Publisher: Elsevier
Start Page: 192
End Page: 208
Journal / Book Title: Advances in Water Resources
Volume: 127
Copyright Statement: © 2019 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence
Keywords: 0905 Civil Engineering
0907 Environmental Engineering
Environmental Engineering
Publication Status: Published
Embargo Date: 2020-03-23
Online Publication Date: 2019-03-23
Appears in Collections:Faculty of Engineering
Earth Science and Engineering

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