Hello,
I am solving the stokes equations on the MAC grid using DMStag with an
approximate Schur complement based preconditioner. The preconditioner
needs a subdomain solve of the Poisson equation on both the velocity as
well as the pressure space. I am using multigrid preconditioned CG for
both the subdomain solves. While the subdomain solve on the velocity
space converges in 4-5 iterations and is independent of mesh-size, the
pressure solve is not mesh-size independent. Relevant information:
Pressure space operator has Neumann boundary conditions.
Coarse-grid operators are being generated using the Galerkin approach (A
= P*Af*Pt) for both of the subdomains.
For the pressure space, the jacobi and sor smoothers were tried with
several omega and damping parameter choices.
Symmetric smoothing (same number of pre- and post-smoothing iterations)
Has anyone tried solving the poisson operator on the cell-centered
pressure space with DMStag? Or know what might be going wrong with the
mg-cg convergence?
Thanks!
-Gautam
