On Wed, 13 Mar 2019, Renato Poli wrote:
> In the same run (other timesteps), I also see DIVERGED_INDEFINITE_MAT. > In many timesteps it converges. It happens sometimes... > I am using LU preconditioners. Built-in PETSc LU? If so then you might try MUMPS or you might try different dof ordering options; I've seen each of those fix LU failures in the past. > I have a 2D circumference inside the domain (petroleum wellbore). > I need to set a Neumann BC (total oil rate), but the pressure must be > constant in the circumference. That... sounds like it'll be well-defined even in the discrete case (N-1 constraints for strong enforcement of that constant, 1 summed BC for total flow rate) but it couldn't hurt to check what the matrix conditioning looks like. > Similar to a distributed total force in a rigid plate - for mechanical > solvers. > > My approach: > 1) select a DOF for the circumference. > 2) tie all other DOFs in the circumference to this one with > "add_constrain_row". Darcy flow, using one LAGRANGE variable for pressure I assume? > Can you see another way to do that? Add a SCALAR variable to use as a Lagrange multiplier? We don't have any examples corresponding to your case precisely but systems_of_equations_ex3 and ex5 might be helpful. --- Roy _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
