code_saturne User's Forum

Hello all,

I am now using version 3.0.0 of Saturne, having upgraded from version 2.0.4. I am having trouble with my boundary conditions. I have read through the theory manual and looked in some of the subroutines and I thought that I understood what I was doing...

I am trying to apply Robin type boundary conditions to my flows. I managed to make all of this work in version 2.0.4 but I can't seem to figure out how to do it now.

In version 2.0.4 my understanding was that the gradient condition provided the values needed to work out grad(U) at the cell centre, and the flux boundary conditions were used to work out grad(U) at the boundary face. Is this correct? And has this changed in version 3.0.0?

I am frustrated because my simulations converged in version 2.0.4 but don't do in verison 3.0.0...

Thank you all for your time.

Hello,

The boundary condition formulation has changed in version 3.0. The new formulation is described in the theory guide.

Anyway this new formulation should not have any impact in the user setups (only if rcodcl and icodcl arrays are used to impose your BCs in cs_user_boundary_conditions.f90).

Could you post your dataset on this forum? This may help us to find the issue.

Regards,
JF

There are a lot of subroutines and 4 input data files for the case I am looking at, so it might be a little bit messy to start posting them here.

Hi,

as already wrote Jacques, we have changed the writing of the diffusive boundary conditions coefficients. It is up to date in the theory guide. It was done for conveniency purpose and everything which was possible in 2.0 is in 3.0, just a matter of rewriting.

By the way, it is formally forbidden to fix the value of the velocity (Dirichlet BC) AND the value of the gradient (dot the normal) (Neumann BC). As you wrote, the only possibility is to link the two, which is called a Robin type BC.

Best Regards,

Martin