[dune-pdelab] Access to another cell in alpha_skeleton

[Jonas Beddrich]

Hi Bernd and Dominic,

Thank you very much for you fast replies. Mainly, I wanted to make sure,
that there is no easy work around before creating my own set of grid
operators. Since the inner workings of the assembler and assembler_engines
seem straight forward to me, I’ll give the hacking approach a shot.

I’ll also take a look at the Dumux variant, even though I’d prefer to use
pdelab.

Best regards,
Jonas

Flemisch, Bernd <bernd.flemisch at iws.uni-stuttgart.de> schrieb am Mo. 6.
Juli 2020 um 17:20:

> Hi Jonas,
>
>
> as Dominic points out, we have a NLTPFA implementation in Dumux. I think
> that this currently is still in a private application module, hosted by
> Martin Schneider (in cc). But it uses the same technical infrastructure as
> our publicly available linear MPFA, a pointer to the class documentation
> would be at
> https://dumux.org/doxygen/master/a01630.html#ga82ff36ab4394ccafc81a0750fca4c69e.
> The simplest one-phase incompressible test "test_1p_incompressible_mpfa"
> can be found at
> https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/tree/master/test/porousmediumflow/1p/implicit/incompressible.
> The discretization is based on the core modules only without involving
> PDELab.
>
>
> Kind regards
>
> Bernd
>
>
> --
> _________________________________________________________________
>
> Bernd Flemisch
> IWS, Universität Stuttgart               phone: +49 711 685 69162
> Pfaffenwaldring 61
> <https://www.google.com/maps/search/Pfaffenwaldring+61?entry=gmail&source=g>
>             email: bernd at iws.uni-stuttgart.de
> D-70569 Stuttgart           url: www.iws.uni-stuttgart.de/en/lh2/
> _________________________________________________________________
> ------------------------------
> *Von:* dune-pdelab <dune-pdelab-bounces at lists.dune-project.org> im
> Auftrag von Dominic Kempf <dominic.r.kempf at gmail.com>
> *Gesendet:* Montag, 6. Juli 2020 16:41:48
> *An:* Jonas Beddrich
> *Cc:* dune-pdelab at lists.dune-project.org
> *Betreff:* Re: [dune-pdelab] Access to another cell in alpha_skeleton
>
> Hey Jonas,
>
> welcome to PDELab! I wished I had a better welcoming gift to you...
>
> I am assuming that the scheme you are trying to implement is something
> like Figure 1b from
> "Nonlinear two-point flux approximation for modelingfull-tensor effects in
> subsurface flow simulations"
> by Chen et al. - correct me if I am wrong.
>
> We get this question and variations of it a lot, and unfortunately the
> most adequate answer is:
> The assumption that a facet integral only depends on the two neighboring
> cells
> is built quite deeply into the PDELab assembler. That being said, there is
> no clean solution to
> your problem in PDELab.
>
> I know that DuMux (www.dumux.org, a downstream project) has treated that
> problem before.
> I am not sure they are relying on the PDELab assembler in their
> implementation, but it is worth
> asking them.
>
> Of course, things can always be hacked. Most probably one can do something
> with precomputation
> of all flux values at all intersection mid points, but I am not sure about
> the details (e.g. I have no
> clues about how jacobians for such a system could be computed).
>
> Best,
> Dominic
>
> On Mon, Jul 6, 2020 at 3:30 PM Jonas Beddrich <jonas.beddrich at gmail.com>
> wrote:
>
>> Hi everyone,
>>
>> I'm looking for a method to access the values of cells in the
>> alpha_skeleton function of my local operator in addition to the values of
>> the inside and outside cell of the intersection.
>>
>> The nonlinear Two Point Flux Approximation I'm currently working on
>> requires information about 4 cells to compute the flux through each
>> intersection. So in addition to the inside and outside cell two additional
>> cells m and k are required. The cells m and k are dependent on the
>> intersection, the inside and outside cell as well as problem parameters.
>> Right now I can determine the index of those cells and then get the
>> corresponding elements by iterating over the grid.
>>
>> Sadly, I haven't found an efficient way to access the values of these
>> cells, since alpha_skeleton only gets the local vectors and local function
>> spaces of the inside and outside cell. But I guess I'm not the only person
>> encountering this problem. Can anyone give me a hint on how to solve this?
>>
>> Best regards,
>> Jonas
>> _______________________________________________
>> dune-pdelab mailing list
>> dune-pdelab at lists.dune-project.org
>> https://lists.dune-project.org/mailman/listinfo/dune-pdelab
>
> --
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