Simultaneous fine and course Meshes for two parts of a solver
 

Hello All.
I have built a solver which solves turbulent mixed convection flow and Radiation heat transfer in a vertical parallel plates channel.
Does anyone know that how we can set different meshes for these two parts? I mean because radiation doesn't need a very fine mesh, can we set a course mesh for solving RTE and at the same time a fine mesh for flow part?
As you may know, after each iteration in RTE solution, result goes to energy equation via source term. Then the flow equations are solved for one iteration and this procedure goes on.
Best Regards,
Mas