Influence of Marangoni-driven flows on A + B $\rightarrow$ C reaction fronts

When the two reactants of an A + B $\rightarrow$ C reaction are brought into contact, a reaction front is formed and the spatially localized zone where the reaction occurs evolves in time due to the interdiffusion of A and B. The properties of such fronts are well studied in reaction-diffusion systems where no flow can affect the dynamics. Here we consider horizontal aqueous solutions where the three species A, B, and C can affect the surface tension of the solution, thereby driving Marangoni flows. The resulting dynamics is studied by numerically integrating the incompressible Navier-Stokes equations coupled to reaction-diffusion-convection equations for the three chemical species. We show that the front propagation cannot be predicted anymore on the sole basis of the reaction-diffusion properties as was still possible in the presence of buoyancy-driven flows around such fronts. We relate this observation to the structure of the Marangoni-driven flow and propose a classification of the convective effects on A + B $\rightarrow$ C reaction fronts as a function of the different Marangoni numbers quantifying the effect of each species on the surface tension.