On Fri, Apr 17, 2020 at 1:58 PM Roberto Federico Ausas <rfausas@icmc.usp.br> wrote:
Hello,
Thanks for your answer. The solution you provided worked.

Effectively, I was using Fenics, but then I needed to switch to firedrake because of the possibility of using Hermite elements to solve the structure part (a Kirchhoff beam). In the FSI interaction scheme I'm thinking, I will probably need a few dozens of variables belonging to R spaces (these essentially are the dofs associated with the beam problem). I hope the strategy you provided will work as well in such a case. Another difficulty I will face is that in order to construct the residual of my problem, I will need to integrate over the fluid and the beam meshes, the coupling being done through these Real space variables. A fully monolithic approach is probably out of question.

Hermite is certainly a way to go for beams, but have you looked at the Morley element?

  Thanks,

     Matt
 
Regards











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Today's Topics:

   1.  Issue solving problem involving function in R space
      (Roberto Federico Ausas)
   2. Re:  Issue solving problem involving function in R space
      (Patrick Farrell)


----------------------------------------------------------------------

Message: 1
Date: Fri, 17 Apr 2020 00:22:02 -0300
From: Roberto Federico Ausas <rfausas@icmc.usp.br>
To: firedrake@imperial.ac.uk
Subject: [firedrake] Issue solving problem involving function in R
        space
Message-ID:
        <CAH6Ec4msgbi57NxOuLHB-W3LZm1yzhpa86DORwdobSWr2KmEUg@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Hello,

I need to solve a problem involving functions belonging to an R space.

For robustness, I need to use direct solvers for the linear part, but I'm
getting the following:

ValueError: Monolithic matrix assembly is not supported for systems with
R-space blocks.

Is there any way of doing this?
Any help would be appreciated
Regards

--
Roberto F. Ausas
Instituto de Ci?ncias Matem?ticas e de Computa??o - ICMC/USP
S?o Carlos, SP - Brasil
*http://www.lmacc.icmc.usp.br/~ausas* <http://www.lmacc.icmc.usp.br/~ausas>
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Message: 2
Date: Fri, 17 Apr 2020 08:48:59 +0100
From: Patrick Farrell <patrick.farrell@maths.ox.ac.uk>
To: firedrake@imperial.ac.uk
Subject: Re: [firedrake] Issue solving problem involving function in R
        space
Message-ID: <4e5c170e-23f7-73e6-f867-17a7918e5161@maths.ox.ac.uk>
Content-Type: text/plain; charset=utf-8; format=flowed

Hi Roberto,

I've solved this before. Please see the solver options in
tests/regression/test_moore_spence.py:

https://github.com/firedrakeproject/firedrake/blob/master/tests/regression/test_moore_spence.py#L77

The idea is to use a fieldsplit to take the Schur complement onto
the R block; solve the top-left block with LU, and use GMRES on the
Schur complement. Since the Schur complement is 1x1 it will solve in
one iteration without a preconditioner.

A warning: support for problems with variables in R is not great
in firedrake. It's probably the one area (that I use) where firedrake's
support is painfully weaker than FEniCS'.

Patrick

On 17/04/2020 04:22, Roberto Federico Ausas wrote:
> Hello,
>
> I need to solve a problem involving functions belonging to an R space.
>
> For robustness, I need to use direct solvers for the linear part, but I'm getting the following:
>
> ValueError: Monolithic matrix assembly is not supported for systems with R-space blocks.
>
> Is there any way of doing this?
> Any help would be appreciated
> Regards
>
> --
> Roberto F. Ausas
> Instituto de Ci?ncias Matem?ticas e de Computa??o- ICMC/USP
> S?o Carlos, SP - Brasil
> _http://www.lmacc.icmc.usp.br/~ausas_
>
> _______________________________________________
> firedrake mailing list
> firedrake@imperial.ac.uk
> https://mailman.ic.ac.uk/mailman/listinfo/firedrake
>




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End of firedrake Digest, Vol 40, Issue 8
****************************************


--
Roberto F. Ausas
Instituto de Ciências Matemáticas e de Computação - ICMC/USP
São Carlos, SP - Brasil
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