Stirring rate effects in the Belousov-Zhabotinskii reaction

Queiroz JP, Faria RB. The Chlorate-Nitrous Acid-Iodine-Iodide Oscillating Reaction

This work presents a new oscillating reaction based on chlorate and observed in a CSTR at room temperature. This can be the first member of a new family of oscillating reactions. In addition, it is also the first oscillating reaction to use nitrous acid as a reactant. Four different behaviors were observed: simple oscillations, mixed mode oscillations, bursts, and quasiperiodicity. The period of oscillations is very short, which is around 1 s. Together with the fact that it also shows fast bursts, it opens the possibility that it can be used to simulate fast biological events, like the neuron's communications signals.

Stirring-Controlled Bifurcations in the 1,4-Cyclohexanedione−Bromate Reaction

We report the experimental observation that stirring in a closed 1,4-cyclohexanedione-bromate reaction can induce transitions not only between oscillatory and nonoscillatory states but also between simple and period-doubled oscillations. Notably, the transition from simple to complex oscillations occurs as a result of increasing stirring rate. When illumination was employed to characterize the importance of microfluctuations of concentrations, the threshold stirring rate for inducing a bifurcation was found to increase proportionally to the intensity of the applied light. Numerical simulations with an existing model illustrate that the experimental phenomena could be qualitatively reproduced by considering effects of mixing on diffusion-limited radical reactions, namely, the disproportion reaction of hydroquinone radicals.

Homogenization induced by chaotic mixing and diffusion in an oscillatory chemical reaction

A model for an imperfectly mixed batch reactor with the chlorine dioxide-iodine-malonic acid (CDIMA) reaction, with the mixing being modelled by chaotic advection, is considered. The reactor is assumed to be operating in oscillatory mode and the way in which an initial spatial perturbation becomes homogenized is examined. When the kinetics are such that the only stable homogeneous state is oscillatory then the perturbation is always entrained into these oscillations. The rate at which this occurs is relatively insensitive to the chemical effects, measured by the Damköhler number, and is comparable to the rate of homogenization of a passive contaminant. When both steady and oscillatory states are stable, spatially homogeneous states, two possibilities can occur. For the smaller Damköhler numbers, a localized perturbation at the steady state is homogenized within the background oscillations. For larger Damköhler numbers, regions of both oscillatory and steady behavior can co-exist for relatively long times before the system collapses to having the steady state everywhere. An interpretation of this behavior is provided by the one-dimensional Lagrangian filament model, which is analyzed in detail.