Hi,
I managed to figure out the solution myself. I was not initializing
properly the matrix_bc entries and I was missing part of the inhomogeneous
boundary condition loop, as I mentioned in the previous message. I still
have one conceptual question though: why setting the initial temperature
(and hence the boundary conditions) to a constant leads to my system being
in-homogeneously constrained?
Thank you for your time.
Le jeudi 27 juin 2024 à 11:12:47 UTC+3, Tomas Fernandez Bouvier a écrit :
> Sorry I didn't explain myself properly. On the other hand I have a better
> understanding on the problem now.
>
> Long short story: Instead of setting the initial temperature to 0 as in
> most of the examples, I set it to 1. When I tried to solve the system I saw
> the artifact that I showed in the previous picture. The program was
> reporting that I had in-homogeneous boundary conditions, that's why I
> titled my question like that. But I am now sure that every quadrature point
> in the system is set to 1 and yet when solving the first step I still have
> a smaller value that appears in the adjacent points to the boundary. I
> created a minimally refined lattice and the error persists.
>
> Le mercredi 26 juin 2024 à 18:51:55 UTC+3, Wolfgang Bangerth a écrit :
>
>>
>> Tomas,
>> I must admit that I don't understand what the issue is. What does the
>> image show, and what is it you expect it to show? Part of my confusion
>> is that you use terms initial conditions, right hand side, and (in the
>> Subject line) constraints, but these are not obviously related to each
>> other.
>>
>> It is, of course, possible that step-32 has a bug that prevents it from
>> dealing correctly with non-zero initial conditions but that doesn't show
>> up with the zero initial conditions used there.
>>
>> Best
>> W.
>>
>> On 6/26/24 07:32, Tomas Fernandez Bouvier wrote:
>> > *** Caution: EXTERNAL Sender ***
>> >
>> > EDIT:
>> >
>> > I fixed the problem that involved inhomogeneous constraints (i had not
>> > initialized the bc matrix). However I am still struggling since
>> boundary
>> > conditions are only being interpolated on the external face of my
>> > boundary cells.
>> >
>> >
>> > Le mercredi 26 juin 2024 à 14:00:46 UTC+3, Tomas Fernandez Bouvier a
>> écrit :
>> >
>> > In the context of a parallel implementation of step-26, where I
>> > inspired myself in step-32, I am trying to set a different constant
>> > in the initial and boundary conditions that I apply to my system.
>> > Below is an image of the result when I set the initial system to 1
>> > instead of 0. I tried to investigate the implementation of a rhs.
>> > Somehow the conditions appear to be inhomogeneous and therefore the
>> > rhs is modified. The only improvement that I got was when I muted
>> > this lines in my code:
>> >
>> > if (constraints.is_inhomogeneously_constrained(
>> > data.local_dof_indices[i]))
>> > {
>> > for (unsigned int j = 0; j < dofs_per_cell; ++j)
>> > data.matrix_for_bc(j, i) +=0 ;
>> > /*
>> > (scratch.phi_T[i] * scratch.phi_T[j] *
>> > (use_bdf2_scheme ? ((2 * time_step +
>> > old_time_step) /
>> > (time_step +
>> > old_time_step)) :
>> > 1.) ) *
>> > scratch.fe_values.JxW(q);
>> > */
>> > }
>> >
>> > but I am still not able to set the entire system initial temperature
>> > to 1 or any other initial value.
>> >
>> > Can you help me?
>> >
>> > Thank you!
>> >
>> >
>> >
>> > Screenshot from 2024-06-26 13-55-07.png
>> >
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>> <
>> https://groups.google.com/d/msgid/dealii/efb4046c-8d37-4243-8dba-bc959af2b0dan%40googlegroups.com?utm_medium=email&utm_source=footer>.
>>
>>
>>
>
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