Reaction front dynamics under shear flow for arbitrary Damköhler numbers

International audienceReaction fronts where two reactive fluids displace one another play an important role in a range of applications,including contaminant plume transport and reaction, soil and aquifer remediation, CO2 sequestration, geothermaldipoles and the development of hotspots of reaction in mixing zones. The background flow induces enhancedmixing, and therefore reaction, through interfacial shear. Hence the coupling of fluid flow with chemical reactionsis pivotal in understanding and quantifying effective reaction kinetics in reaction fronts. While this problem hasbeen addressed in the limit of fast reactions (e.g. de Simoni 2005, Le Borgne 2014), in natural systems reactionscan span a large range of Damköhler numbers since their characteristic reaction times vary over a large range oftypical values. Here the coupling of shear flow and reversible chemical reactions is studied for a reaction front withinitially separated reactants at arbitrary Damköhler numbers. Approximate analytical expressions for the globalproduction rate are derived based on a reactive lamella approach. We observe three distinct regimes, each of themcharacterized by different scalings of the global production rate and width of the reactive zone. We describe thedependency of these scalings and the associated characteristic transition times as a function of Damköhler and Pécletnumbers. These results are validated against 2D numerical simulations. The study is expected to shed light onthe inherently complex cases of reactive mixing with varying reaction rates under the influence of an imposed flow.de Simoni et al. (2005) Water Resour. Res., 41, W11410Le Borgne et al. (2014) GRL, 41(22), 789