Department of Electrical Engineering, Yamaguchi University, Tokiwadai 2557, Ube 755, Japan
(Received November 5, 1988; Accepted November 10, 1988)
Keywords: BZ Reaction, Hydrodynamic Instability, Pattern Dynamics, Dynamic Image Processing
Chemical patterns, such as target patterns and spiral waves, caused by propagation of chemical waves in a non-stirred Belousov-Zhabotinsky (BZ) reaction are known as typical examples of spontaneous pattern formations in non-equilibrium systems. These phenomena have attracted much attention because of an analogy with the selforganization in biological systems. Here, we report on experimental studies of pattern dynamics in the BZ-reaction and its accompanying hydrodynamic phenomena, and briefly mention recent developments in this field. The image processing techniques introduced for analysis of the pattern dynamics and hydrodynamic phenomena are also discussed. The mechanism of spontaneous pattern formation in the ferroin-catalyzed BZ reaction was investigated by two-dimensional spectrophotometry and two-dimensional velocimetry based on a microscope video imaging technique. Hydrodynamic flow accompanying the chemical reaction was measured quantitatively by velocimetry, and a correlation between the pattern dynamics and the hydrodynamic flow was observed by spectrophotometry. Important findings from our recent research are:
1) Oscillatory hydrodynamic flow is induced by periodic passage of spiral wave trains.
2) Periodic deformation and decomposition of chemical wave fronts are caused by the oscillatory flow.
3) A travelling wave of convective flow is excited by circular wave propagation in a well reduced BZ-solution.
4) A chemical wave with high negative curvature may induce a hydrodynamic instability in the BZ-solution.
Mechanisms of these complicated phenomena are extensively discussed.