COMSOL Multiphysics for Efficient Solution of a Transient Reaction-Diffusion System with Fast Reaction

A reaction between chemical species is modeled by a particular reaction pathway, in which one reaction is very fast relative to the other one. The diffusion controlled reactions of these species together with a reaction intermediate are described by a system of three transient reactiondiffusion equations over a two-dimensional spatial domain. In the asymptotic limit of the reaction parameter tending to infinity, an equivalent two component model can be used in numerical simulations that is significantly more computationally efficient. But this model has features such as an unusual coupling of the two components in a boundary condition that bring out important advantages of COMSOL Multiphysics. We discuss the use of COMSOL and present representative simulation results starting with an initial condition with interesting structure throughout the domain.