Simple bimolecular reactions A+B→C can exhibit exotic dynamics, previously observed only in the presence of complex kinetics. When these simple reactions are actively coupled with hydrodynamics, spatio-temporal oscillations of the chemical species concentrations can be induced under isothermal batch conditions.

Abstract

Self-organizing behaviors have long been studied in complex chemical systems involving a nonlinear chemical feedback (e. g. the Belousov-Zhabotinsky and Bray-Liebhafsky reactions). Here we explore the emergence of oscillatory dynamics by coupling simpler chemical processes, in the form of a bimolecular reaction, and natural convection (i. e. flows induced by changes in density and surface tension occurring during the reaction). We study and classify different possible scenarios based on the interplay between chemically-driven Marangoni- (surface tension induced) and buoyancy-driven (density induced) flows. This coupling can either be antagonistic, whereby both generated flows are opposing (e. g. a reaction increasing the surface tension and decreasing the density), or cooperative if both flows act in the same direction (e. g. a reaction increasing both surface tension and density). We further investigate the impact of these oscillations on the mixing and reaction rate.