Hi Hardik, The domain shape is not critical but the element shapes are. Your 100:1 domain aspect ratio is bad if you have N^3 mesh and thus element aspect ratios of 100:1. If that is the case then you probably want to look at semi-coarsening multigrid.
Mark On Fri, May 9, 2025 at 9:55 AM Hardik Kothari <hardik.koth...@corintis.com> wrote: > Dear PETSc team, > > We are solving the Stokes equations using PETSc (via Firedrake) on a > highly anisotropic 3D domain (L_x=1, L_y=0.01, L_z=0.1). > > In this setup, standard Schur complement preconditioners using a mass > inverse for pressure struggle to converge. We could solve the problem with > the LSC preconditioner (solver parameters are shown in the script). > > We have the following questions: > > - Why standard preconditioners struggle in such domains? > - Why is the preconditioned residual norm for the Schur complement > system much higher than the true residual norm? > - Would you recommend alternative or more robust preconditioners for > such geometries? > > > Thank you for your help. > > Best regards, > Hardik > > > > > *HARDIK KOTHARI* > *hardik.koth...@corintis.com* <hardik.koth...@corintis.com> > > Corintis SA > EPFL Innovation Park Building C > 1015 Lausanne > > > > [image: Logo-black.png] > Here at Corintis we care for your privacy. That is why we have taken > appropriate measures to ensure that the data you have provided to us is > always secure >
