Characterization of Bimolecular Reactive Transport in Heterogeneous Porous Media

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• 作者：Yaniv Edery ; Giovanni M. Porta ; Alberto Guadagnini…
• 关键词：Reactive solute transport ; Heterogeneous conductivity fields ; Numerical simulation ; Particle tracking ; Preferential pathways formation
• 刊名：Transport in Porous Media
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：115
• 期：2
• 页码：291-310
• 全文大小：4,255 KB
• 刊物类别：Earth and Environmental Science
• 刊物主题：Earth sciences
  Geotechnical Engineering
  Industrial Chemistry and Chemical Engineering
  Civil Engineering
  Hydrogeology
  Mechanics, Fluids and Thermodynamics
  
• 出版者：Springer Netherlands
• ISSN：1573-1634
• 卷排序：115

文摘

We characterize the role of preferential pathways in controlling the dynamics of bimolecular reactive transport in a representative model of a heterogeneous porous medium. We examine a suite of numerical simulations that quantifies the irreversible bimolecular reaction \(A+B\rightarrow C\), in a two-dimensional heterogeneous domain (with log-conductivity, Y), wherein solute A is injected along an inlet boundary to displace the resident solute B under uniform (in the mean) flow conditions. We explore the feedback between the reactive process and (a) the degree of system heterogeneity, as quantified by the unconditional variance of Y, \(1 \le \sigma _Y^2\le 7\), representing moderately to strongly heterogeneous media, and (b) the relative strengths of advective and diffusive mechanisms, as quantified by a grid Péclet number, \(\textit{Pe}_ {\Delta }\). Our analysis is based on the identification of particle preferential pathways, focusing on particle residence time within cells employed to discretize the flow domain. These preferential pathways are formed mainly by high conductivity cells and generally contain an important component of (sometimes isolated and a relatively small number of) lower conductivity values. A key finding of our analysis is that while the former dominate the behavior, the latter are shown to provide a non-negligible contribution to the global number of reactions taking place in the domain for strongly heterogeneous media, i.e., for the largest investigated values of \(\sigma _Y^2 \). Reactions are detected across the complete simulation time window (of about 5.5 pore volumes) for the strongly advective case. When diffusion plays an important role, the reactive process essentially stops after the injection of a limited amount (\(\sim \)2.5) of pore volumes.