Impact of fluid deformation on mixing-induced chemical reactions in heterogeneous flows

Tanguy Le Borgne (1) , Timothy Ginn (2) , Marco Dentz (3)

1 GR - Géosciences Rennes
2 UC - University of California
3 IDAEA - Institute of Environmental Assessment and Water Research

Fast chemical reactions in geophysical flows are controlled by fluid mixing, which perturbs local chemical equilibria and thus triggers chemical reactions. Spatial fluctuations in the flow velocity lead to deformation of material fluid elements, which form the support volumes of transported chemical species. We develop an approach based on a lamellar representation of fluid mixing that provides a direct link between fluid deformation, the distribution of concentration gradients, and the upscaled reaction rates for fast reversible reactions. The temporal evolution of effective reaction rates is determined by the flow topology and the distribution of local velocity gradients. This leads to a significant increase of the reaction efficiency, which turns out to be orders of magnitude larger than in homogeneous flow. This approach allows for the systematic evaluation of the temporal evolution of equilibrium reaction rates and establishes a direct link between the reaction efficiency and the spatial characteristics of the underlying flow field as quantified by the deformation of material fluid elements.

Mots clés: reactive transport; mixing; fluid deformation; flow topology; lamella; porous media

Domaines: Sciences de la Terre

Tanguy Le Borgne, Timothy Ginn, Marco Dentz. Impact of fluid deformation on mixing-induced chemical reactions in heterogeneous flows. Geophysical Research Letters, 2014, 41 (22), pp.7898-7906. ⟨10.1002/2014GL062038⟩. ⟨insu-01102599⟩