5.2.1 Coupling

If possible one would try to avoid constructing a merged hydrodynamics plus radiation transport scheme.

Instead one constructs and tests a hydrodynamics and a radiation transport scheme separately.

The coupling can be done via operator splitting or adding.

Often radiation transport requires small time-steps to achieve stability.

These can be handled by

• sub-steps for the radiation transport (many small radiation steps per large hydrodynamics step)
• or by an implicit treatment of the radiation transport (while the hydrodynamics operator is still explicit).