[petsc-users] GAMG and linear elasticity

[Jed Brown]

Tabrez Ali <stali at geology.wisc.edu> writes:

> I had missed PCSetCoordinates in ex56.
>
> So is there a correspondence b/w the coordinates [0.x 0.y 0.z 1.x 1.y  
> 1.z ...] passed to PCSetCoordinates/MatNullSpaceCreateRigidBody and  
> the solution vector [0.ux 0.uy 0.uz ...]? 

MatNullSpaceCreateRigidBody assumes that you are in displacement form
with this association.  It just uses the coordinates to create the three
translations and three rotations (in 3D).

> What happens when I am solving the poroelasticity problem where there
> is an additional pressure field associate with each node?

Create your own near null space: 6 rigid body modes plus 1 constant
pressure mode.  Look at the code for MatNullSpaceCreateRigidBody for a
start.
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