Spiral Waves: Recreating the BZ reaction in COMSOL

The Belousov–Zhabotinsky (BZ) reaction is a chemical oscillator: in a thin dish its colour changes in waves, and those waves curl up into rotating spirals. I wanted to reproduce this pattern in a simulation.

In COMSOL I solved a two-variable reaction–diffusion model of an excitable medium. Starting from a disordered state, the waves break up and organise themselves into many rotating spirals. I also studied a single travelling front in one dimension, following it in a space–time plot and computing the eigenvalue spectrum of the linearised problem.

Next to it I wrote a much simpler Python version: a cellular automaton with three species where each one beats the next, like rock–paper–scissors. It produces strikingly similar spirals in a few seconds.