[aspect-devel] Problems with periodic boundary conditions

Wolfgang Bangerth bangerth at tamu.edu
Wed Dec 10 08:45:48 PST 2014

On 11/06/2014 06:51 PM, Max Rudolph wrote:
> Thanks for your help. Another way of dealing with the null space
> associated with a net translation (or net rotation in 3D spherical
> geometry) would be to fix the horizontal velocity for one vx degree of
> freedom (essentially a dirichlet boundary condition for one dof). I
> suppose that it would be key to do this in such a way as to keep the
> stiffness matrix symmetric. Then, calculate the net translation or
> linear momentum in the x-direction and subtract it after solving the
> momentum and continuity equations. Would this solve the problem?

Max, did you figure out how to deal with your situation? I recognize 
that it's been a while since you asked your question :-( but still 
wanted to point out that there are parameter settings to allow you to 
remove this null space -- see the null space parameters for the input file.


Wolfgang Bangerth               email:            bangerth at math.tamu.edu
                                 www: http://www.math.tamu.edu/~bangerth/

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