[petsc-users] [petsc-maint] How to impose boundary conditions using DMDA

[Smith, Barry F.]

    Matt,

       How difficult would it be to impose such boundary conditions with DMPlex? Presumably you just connect the mesh up "properly" and it is straightforward?

   Barry


> On Oct 27, 2018, at 10:23 AM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Sat, Oct 27, 2018 at 2:02 AM Fengwen Wang <fwan at mek.dtu.dk> wrote:
> Dear Colleagues,
> 
> 
> 
> I use the finite element method to solve my problem in Petsc.
> 
> 
> 
> Mesh is defined as a  regular mesh using DMDA.  I have a special boundary condition which I  do not know how to impose it in Petsc. 
> 
> 
> 
> In a 2D problem, the domain is unit size, two degrees of freedom per node (u, v). I would like impose the following boundary condition:
> 
> 
> 
> u(x=1) = -v ( y=1) and v(x=1 )= -u (y=1) .
> 
> 
> 
> How can I impose such a boundary condition in Petsc?  
> 
> In a serial code, you could do this just by equating those variables, but in parallel we have no support for such a boundary condition.
> 
>   Thanks,
> 
>      Matt
> Thanks a lot. 
> 
> 
> 
> Best regards
> 
> Fengwen
> 
> 
> 
> 
> 
> ____________________________________________________
> Senior Researcher
> Department of Mechanical Engineering, DTU
> Nils Koppels Allé       
> Building 404    
> 2800  Kgs. Lyngby 
> fwan at mek.dtu.dk
> 
> 
> -- 
> 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
> 
> https://www.cse.buffalo.edu/~knepley/