[petsc-users] How to solve the pressure possion equations with four neuman bc

[Matthew Knepley]

On Fri, Sep 23, 2016 at 9:38 AM, 丁老师 <ztdepyahoo at 163.com> wrote:

> Dear friends:
>      In the projection method for the solution of incompressible flow,  a
> pressure equation with four neuman bcs need to be solved.
> but the pressure matrix is singular. it gives divergence solution.  how to
> solve this kind of equations.
>

Tell the matrix it has a nullspace of constants:

http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatSetNullSpace.html

  Thanks,

    Matt


> Regards
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-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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