Entropy-based critical reaction time for mixing-controlled reactive transport

Chiogna G, Rolle M (2017)

Publication Type: Journal article

Publication year: 2017

Journal

Water Resources Research American Geophysical Union (AGU)

Book Volume: 53

Pages Range: 7488-7498

Journal Issue: 8

DOI: 10.1002/2017WR020522

Abstract

Entropy-based metrics, such as the dilution index, have been proposed to quantify dilution and reactive mixing in solute transport problems. In this work, we derive the transient advection dispersion equation for the entropy density of a reactive plume. We restrict our analysis to the case where the concentration distribution of the transported species is Gaussian and we observe that, even in case of an instantaneous complete bimolecular reaction, dilution caused by dispersive processes dominates the entropy balance at early times and results in the net increase of the entropy density of a reactive species. Successively, the entropy of the reactant decreases until it vanishes. We show the existence of a unique critical value of dilution, which corresponds to the complete consumption of one of the reactants. This critical dilution index is independent of advective and dispersive processes, and depends only on the dimensionality of the problem, on the stoichiometry of the reaction and on the initial concentrations of the reactants. Furthermore, we provide simple analytical expressions to compute the critical reaction time, i.e., the time at which the critical dilution index is reached, for selected flow configurations. Our results show that, differently from the critical dilution index, the critical reaction time depends on solute transport processes such as advection and hydrodynamic dispersion.

Authors with CRIS profile

Gabriele Chiogna

Involved external institutions

Technische Universität München (TUM) DE Germany (DE) Technical University of Denmark / Danmarks Tekniske Universitet (DTU) DK Denmark (DK)

How to cite

APA:

Chiogna, G., & Rolle, M. (2017). Entropy-based critical reaction time for mixing-controlled reactive transport. Water Resources Research, 53(8), 7488-7498. https://doi.org/10.1002/2017WR020522

MLA:

Chiogna, Gabriele, and Massimo Rolle. "Entropy-based critical reaction time for mixing-controlled reactive transport." Water Resources Research 53.8 (2017): 7488-7498.

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