imrgra is an integer so remove the .d0. If you type "code_saturne compile" whilst in the SRC folder it will tell you any issues which might save you time waiting for answers on here. The subroutines you use are up to you. But I believe usclim and usini1 are required yes. You might also wan...
Try changing gradient reconstruction to least squares by partial extended neighbourhood. Write in usini1 (in the usipsu subroutine, i.e. near where you set the time-step): imrgra = 3. You currently have it to solve by iterative reconstruction of non-orthogonalities. If you want to stick with this bu...
If you think the coupling is a problem then I think you could (as I previously suggested) make a simpler example in 2D. This way it will be easier to find where the problems are. Afraid I cannot provide help with coupling as I do not use it any more. Having no outlet is fine, just give the surface a...
The Courant number is not set how you suggest, that is merely defining an output. If you're keeping parameters the same but shrinking the cell size you will also need to reduce your time-step to keep the same CFL. Given that your simulation ran previously and you have only changed the mesh then you ...
The solver is diverging for turbulent dissipation. It's hard to give advice when that is all the info about the error you give. Given that you've just refined the mesh it could be that your new mesh is not of good enough quality (have you checked for this?). Or the cells are much smaller and you've ...