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Reactive mixing in heterogeneous porous media flows: concentration gradient distribution, spatial intermittency and temporal scaling of effective reaction kinetics

Abstract : Reactive mixing processes play a central role in a range of porous media systems, including CO2 sequestration operations, reactive geothermal dipoles, biofilms, or flow-through reactors. Many of these reactions are limited by fluid mixing processes that bring the reactants into contact. Hence, the temporal dynamics of effective global reactivity is determined by the creation of concentration gradients by fluid stretching and their dissipation by diffusion [1,2]. From the analysis of the elongation and aggregation of lamellar structures formed in the transported scalar fields, we derive analytical predictions for the probability density functions of concentration gradients in heterogeneous Darcy flows over a large range of Péclet numbers and permeability field variances. In this framework, we show that heterogeneous Darcy fields generate highly intermittent concentration fields, as manifested by the spatial scaling of structure functions. The resulting effective reaction rates display a range of temporal behaviors that depend on the degree of heterogeneity. In the large Damköhler limit, we derive analytical expressions for these temporal scalings in the different regimes that arise when exploring the Péclet number space. We generalize these results for different random flows, including turbulent flows. References: [1] Le Borgne, T., M. Dentz, E. Villermaux, The lamellar description of mixing in porous media, J. of Fluid Mech., vol. 770, pp. 458-498 [2] Le Borgne, T., M. Dentz, E. Villermaux, Stretching, coalescence and mixing in porous media, Phys. Rev. Lett., 110, 204501 (2013)
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https://hal-insu.archives-ouvertes.fr/insu-01241980
Contributor : Isabelle Dubigeon <>
Submitted on : Friday, December 11, 2015 - 11:37:21 AM
Last modification on : Thursday, January 23, 2020 - 6:22:07 PM

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  • HAL Id : insu-01241980, version 1

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Tanguy Le Borgne, Marco Dentz, Timothy Ginn, Emmanuel Villermaux. Reactive mixing in heterogeneous porous media flows: concentration gradient distribution, spatial intermittency and temporal scaling of effective reaction kinetics. AGU Fall Meeting 2015, American Geophysical Union, Dec 2015, San Francisco, United States. pp.H24A-02. ⟨insu-01241980⟩

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