BOUNDARY-LAYER ANALYSIS OF WAVES PROPAGATING IN AN EXCITABLE MEDIUM -MEDIUM CONDITIONS FOR WAVE-FRONT-OBSTACLE SEPARATION

In an excitable medium, wave breaks are essential for spiral wave form ation. Although wave breaks can result from collisions between a wave and an obstacle, it is only when the resultant wave fragments separate from the obstacle (wave-front-obstacle separation) that a spiral wave will begin to develop. We explored collisions between a piecewise lin ear obstacle and an incident wave front while varying the excitability of the media and the angle between the linear obstacle segments. Wave -front-obstacle separation was observed to occur within the small boun dary layer of the order of the wave-front thickness. Conditions for wa ve-front-obstacle separation were determined by the relationship betwe en reaction-diffusion flows within this boundary-layer region. We deve loped a theoretical characterization of the boundary-layer region that permits estimation of the critical values of medium parameters and ob stacle geometry that define the transition from wave-front-obstacle at tachment to wave-front-obstacle separation. Theoretical predictions re vealed good agreement with results of the numerical simulations.