Thermal convection in reaction fronts confined between conductive walls

Abstract

Exothermic autocatalytic reaction fronts propagating between two conductive walls shows an increase of speed and change in shape due to buoyancy driven convection. We modeled the system using reaction-diffusion-advection equations for chemical concentration and temperature. In these equations, a cubic autocatalytic exothermic reaction leads to a propagating front. The fluid flow is determined by the Stokes equation allowing for density changes due to thermal expansion. The front propagates in a liquid confined in a narrow rectangular domain resembling a two dimensional tube. Fluid motion enhances the front speed and modifies its curvature. In vertical domains, a transition to a nonaxisymmetric front takes place as the width increases. Heat conductivity across the walls delays the transition to larger critical widths. We find regions of bistability between nonaxisymmetric fronts and lower speed fronts at different values of conductivity. Heat losses diminish convection in horizontal tubes, resulting in a decrease of front speed.