A tomographic study of desynchronization and complex dynamics of scroll waves in an excitable chemical reaction with a gradient

Abstract

The evolution of scroll waves in an excitable chemical medium with a gradient parallel to the scroll filament is studied. Depending on the excitability and the gradient, twisted scroll waves and scroll wave attachment to the boundary of the reaction volume are observed by optical tomography, which allows the full three-dimensional reconstruction of the vortex structure in the Belousov–Zhabotinsky reaction as well as estimates on the shape and dynamics of the organizing center of the scroll (the filament). This behavior is reproduced in numerical simulations with the generic Barkley model for excitable media supplemented by a gradient along the filament. In particular, the study deals with scroll waves in a cylindrical reaction system with a free surface open to the air. Oxygen penetrating through the free surface inhibits the evolution of waves and establishes a twist of the filament. Cooling of the reaction system enhances this twist, eventually leading to a bending of the initially straight filament. Finally, the bending becomes so pronounced that the filament touches the container boundary and breaks into two pieces, each of which has its distinct rotation frequency.