Session AM - Chaos and Fractals.
ORAL session, Sunday morning, November 23
Saratoga, SMH
We present results of experimental studies of pattern formation in the Belousov-Zhabotinsky (BZ) chemical reaction in a blinking vortex flow. The flow is based on the model first proposed by Aref in 1984 to demonstrate chaotic advection. The flow is generated using a magnetohydrodynamic forcing technique, and the system can be filled either with an aqueous solution (for mixing studies) or the chemicals used for the BZ reaction. The patterns that develop for the BZ system are compared with those observed for the mixing of a passive impurity in the same flow. A mixing time is defined based on the intersection of graphs of decaying striation thickness (for the mixing of a passive impurity) and growing diffusive length scales. For the BZ experiments, if the mixing time is significantly smaller than typical correlation times for the BZ oscillation, then large-scale patterns form. If the mixing time is larger, then smaller-scale patterns form. The same sort of analysis is used to describe BZ patterns in an oscillating vortex chain, a system for which the mixing is also chaotic.