Fronts and trigger wave patterns in an array of oscillating vortices

We present experiments on reaction fronts and self-sustaining trigger wave patterns in an advection-reaction-diffusion system with chaotic mixing. The flow is a two-dimensional array of oscillating vortices, and the reaction is the excitable Belousov-Zhabotinsky chemical reaction. Reaction fronts are found to mode-lock for a wide range of frequencies, and the mode-locking results in “faceted” fronts that line up along the directions of the underlying vortex array. Self-sustaining trigger wave patterns are also found composed of large scale spiral and spiral-pair patterns, similar to patterns in the reaction-diffusion (no flow) limit but with a significantly larger typical length scale and with clear anisotropy that reflects the vortex array