## Some details you have to be aware of

A coupled simulation involve different codes that exchange data in order to improve physical predictions.
For aerothermal computations with fluid dynamics, conduction and radiation, the type of exchange data are:

- Fluid <-> Conduction: boundary conditions
- Fluid <-> Radiation: volumic source terms
- Radiation <-> Conduction: boundary conditions

The choice of the boundary condition for conjugate heat transfer have an impact on the stability of the numerical problem.
It is then recommanded to:

- Impose the temperature of the solid solver to the fluid one,
- Impose the heat flux of the fluid solver to the solid one.

Thus, you have to choose adequate boundary conditions for AVBP and AVTP. For example:

- AVBP: WALL_NOSLIP_ISOT, WALL_NOSLIP_RELAX_T, WALL_NOSLIP_LOSS, WALL_NOSLIP_CTHFLUX, WALL_WAVE_NOSLIP_ISOT, WALL_LAW(_COUPLED)_ISOT ...
- AVTP: WALL_FLUX, WALL_TEMP_FLUX

In order to ensure that heat fluxes at the wall are available for coupling, you have to turn on the

*istoreadd* parameter in the

*run.dat* file of AVBP to 3.

When radiation is involved in the coupled problem, the only choice consists in:

- Impose the temperature of the solid solver to the radiation one,
- Impose the heat flux of the radiation solver to the solid one,
- Impose the composition of the fluid mixture as well as its temperature and pressure to the radiation solver,
- Impose the radiation source term in the energy equation of the fluid solver.

Thus, for radiation coupling, there are just two things to be aware of: the boundary condition of the thermal solver AVTP must be as described for the fluid/solid coupling (imposition of a flux like condition), and the the radition model in the *input_radiation.dat* of AVBP must be 2 (for coupled model).