Hi Folks, I am trying to solve the momentum equation in a projection preconditioner using GAMG or Hypre solver. The equation looks like for velocity variable *v* looks like:
[image: Screenshot 2024-10-28 at 4.15.17 PM.png] Here, μ is spatially varying dynamic viscosity and λ is spatially varying bulk viscosity. I understand that I need to specify rigid body nullspace modes to the multigrid solver in order to accelerate its convergence. Looking into this routine MatNullSpaceCreateRigidBody() ( https://urldefense.us/v3/__https://petsc.org/release/manualpages/Mat/MatNullSpaceCreateRigidBody/__;!!G_uCfscf7eWS!eKqgIJjCdMzIU76f7X65AmGxrU_-lC7W02BMWafJ77DNf_IuQk6O1X3qU1x9Ez8NJ20vZEL-mF6T1yNmDnwv0eWa2w$ ), I see that I need to provide the coordinates of each node. I am using staggered grid discretization. Do I need to provide coordinates of staggered grid locations? Thanks, -- --Amneet
