Nonlinear waves in a shear flow with a diffusive exothermic reaction and its qualitative reasoning

Abstract

In nonlinear chemical reaction systems, the occurence of the macroscopic structure is well known as the oscillatory pattern formation, the solitary wave, the chaotic behavior and so on. In this paper, the occurrence of nonlinear waves in a liquid shear flow with a diffusive exothermic reaction is reported and its qualitative reasoning using a timed Petri net is investigated. It is considered that the viscosity is a direct effective factor on the occurrence of waves. Such viscous nonlinear waves induced by a diffusive exothermic reaction are experimentally shown and qualitatively analyzed. The waves with the almost constant frequency, about 1.7 Hz, can be detected by visual observation, temperature measurements, and velocity measurements. A qualitative model on the mechanism of oscillation is proposed based on the interaction among concurrent events i.e., reaction, molecular mass transfer, molecular heat transfer, molecular momentum transfer and forced-convective transfer. It is confirmed by Petri net simulations that the relationship of Sc &>; Pr &>; 1 in the liquid phase is closely connected with the continuation of the oscillatory phenomena. Moreover, it is expected that an increase of entire fluid viscosity induces an increase of the frequency, and it can be experimentally confirmed.