Oscillatory flow induced by the coupling between Marangoni and buoyancy-driven convection in a reactive system

When two reactants A and B, initially separated in space, react upon diffusive mixing, the product C can generate connective flows by locally changing the surface tension of the solution or its density.
By means of numerical simulations, we show that, if the reactants are sufficiently more surface-active than the product, a transient Marangoni oscillatory flow can be observed. The antagonistic coupling with buoyancy-driven convection, arising from density changes during the chemical reaction, can enhance the oscillatory instability, leading to self-sustained oscillations.
The dynamics is characterized in the relevant parametric space spanned by the thickness of the solution layer and the Marangoni and buoyancy numbers, quantifying the effect of each chemical on the surface tension and solution density, respectively.