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

[Matthew Knepley]

On Mon, Oct 29, 2018 at 9:37 AM Fengwen Wang <fwan at mek.dtu.dk> wrote:

> Yes.  I would like to a rotational BCs(Twist bcs).
>
You can do that with some work. I have implemented a Mobius strip (see
DM_BOUNDARY_TWIST). However,
I have no idea how to put a function space down on a non-orientable
manifold.

  Thanks,

     Matt


> Such a boundary is needed to reduce the computational domain.
>
>
> Thanks 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:* Lawrence Mitchell <wence at gmx.li>
> *Sent:* Monday, October 29, 2018 1:17:34 PM
> *To:* Matt Knepley
> *Cc:* Fengwen Wang; PETSc; PETSc
> *Subject:* Re: [petsc-users] [petsc-maint] How to impose boundary
> conditions using DMDA
>
>
>
> > On 29 Oct 2018, at 10:56, Matthew Knepley <knepley at gmail.com> wrote:
> >
> > You can certainly map the right edge to the top edge (its topologically
> a square again), but that
> > mapping is not smooth, and I do not know how you would make a global
> basis for the approximation space.
>
> Yeah, I thought this was topologically just a cone, but that would have:
>
> u(x=1) = -v(y=1)
>
> and
>
> v(x=1) = u(y=1) (note matching sign).
>
> So if you wanted the v(x=1) = -u(y=1) there would be a twist somehow, and
> then a discontinuity in the mapping.
>
> Lawrence
>


-- 
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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