CONVECTIVE INSTABILITIES INDUCED BY AN EXOTHERMIC AUTOCATALYTIC CHEMICAL-REACTION

A bistable or excitable exothermic chemical reaction can produce a tra veling front of chemical reactivity upon being triggered. The dynamics of the wave propagation are greatly influenced by the amount of heat generated at the wave front, which in turn is a function of (nonlinear ) reaction kinetics, enthalpy change, and extent of reaction. The chem ical reaction investigated here has shown complex propagative patterns , including accelerating big waves, convective rolls, double-diffusive convection, and spatiotemporal patterns. A model devised to explain t he patterns involves a laterally heated fluid layer in which the basic flow loses stability in the form of hydrothermal waves. Wave motion i s preceded by a global circulation between the hot and cold regions, w ith the velocity being proportional to the lateral temperature gradien t. In this highly exothermic reaction the spatiotemporal patterns can be explained by a stability analysis of the Benard-Marangoni convectio n with lateral heating.