This PR adds an operator splitting implementation intended to support stiff reactions. Specifically, we use Lie splitting within ReactingFlow. The 'spatial' terms, specifically advection-diffusion, are discretized with backward Euler. The 'reaction' terms, including the source term in the temperature equation due to chemical reactions, are discretized with forward Euler at a user-specified subdivision of the advection-diffusion time step. This allows the time step seen by the chemistry to be set arbitrarily small, enabling stable integration of stiff reactions, without affecting the time step of the advection-diffusion component of the system.
This PR adds an operator splitting implementation intended to support stiff reactions. Specifically, we use Lie splitting within
ReactingFlow. The 'spatial' terms, specifically advection-diffusion, are discretized with backward Euler. The 'reaction' terms, including the source term in the temperature equation due to chemical reactions, are discretized with forward Euler at a user-specified subdivision of the advection-diffusion time step. This allows the time step seen by the chemistry to be set arbitrarily small, enabling stable integration of stiff reactions, without affecting the time step of the advection-diffusion component of the system.