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

[Fengwen Wang]

Hi Matt and Barry,


I only have  a regular 2D  square domain of a unit cell.


How can I use DMPlex to apply such a boundary condition?


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
________________________________
From: Matthew Knepley <knepley at gmail.com>
Sent: Monday, October 29, 2018 10:24:36 AM
To: Barry Smith
Cc: Fengwen Wang; PETSc; PETSc
Subject: Re: [petsc-maint] How to impose boundary conditions using DMDA


On Sun, Oct 28, 2018 at 12:18 PM Smith, Barry F. <bsmith at mcs.anl.gov<mailto:bsmith at mcs.anl.gov>> wrote
    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?

If you figure out what topology is meant by this, it should not be hard. However, I
cannot figure out what they mean right now.

  Thanks,

    Matt

   Barry


> On Oct 27, 2018, at 10:23 AM, Matthew Knepley <knepley at gmail.com<mailto:knepley at gmail.com>> wrote:
>
> On Sat, Oct 27, 2018 at 2:02 AM Fengwen Wang <fwan at mek.dtu.dk<mailto: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<mailto: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/



--
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/<http://www.cse.buffalo.edu/~knepley/>
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