[deal.II] Re: Specifying internal "boundary" conditions

[Rene Gassmöller]

Hi Melanie,
we also have a few examples in ASPECT that probably do what you are aiming 
for. E.g. the cookbook prescribed_velocity 
(https://github.com/geodynamics/aspect/blob/master/cookbooks/prescribed_velocity/prescribed_velocity.cc#L295)
 
uses the `add_line` and `set_inhomogeneity` functions to constrain the 
value of the solution to a particular value at a particular location. There 
we still use the deprecated ConstraintMatrix object (that should be 
replaced by the AffineConstraints Bruno mentioned), but the process is more 
or less identical. Let me know if you want to do something similar, but for 
the temperature, I have some code for that elsewhere.

Best,
Rene



On Thursday, September 19, 2019 at 10:55:31 AM UTC-7, Mélanie Gérault wrote:
>
> Dear Bruno,
>
> Thank you, that helps a lot.
>
> Melanie
>
> On Wednesday, September 18, 2019 at 1:58:39 PM UTC-4, Bruno Turcksin wrote:
>>
>> Mélanie,
>>
>> I am not sure I understand exactly what you want to do but often people 
>> who want internal boundary conditions, really just want to impose some 
>> constraints to a few dofs. This can be done using AffineConstraints 
>> . 
>> I am sure that you have seen it in the tutorials where it is used to 
>> constrain hanging nodes and to impose Dirichlet boundary condition. 
>> Basically, you can create one yourself to impose any constraint you want on 
>> any dofs.
>>
>> I hope this help.
>>
>> Bruno
>>
>> On Wednesday, September 18, 2019 at 11:34:12 AM UTC-4, Mélanie Gérault 
>> wrote:
>>>
>>> Hi,
>>>
>>> I am wondering if anyone has ever implemented/used internal boundary 
>>> conditions in deal.II. I need to impose displacements inside of a domain. I 
>>> am assuming that it is feasible with the code, but please let me know if I 
>>> am wrong.
>>>
>>> And in case I need to do it from scratch, I would also appreciate any 
>>> suggestion you may have.
>>>
>>> Thanks a lot!
>>>
>>> Mélanie
>>>
>>

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[deal.II] Re: Specifying internal "boundary" conditions

[Mélanie Gérault]

Dear Bruno,

Thank you, that helps a lot.

Melanie

On Wednesday, September 18, 2019 at 1:58:39 PM UTC-4, Bruno Turcksin wrote:
>
> Mélanie,
>
> I am not sure I understand exactly what you want to do but often people 
> who want internal boundary conditions, really just want to impose some 
> constraints to a few dofs. This can be done using AffineConstraints 
> . 
> I am sure that you have seen it in the tutorials where it is used to 
> constrain hanging nodes and to impose Dirichlet boundary condition. 
> Basically, you can create one yourself to impose any constraint you want on 
> any dofs.
>
> I hope this help.
>
> Bruno
>
> On Wednesday, September 18, 2019 at 11:34:12 AM UTC-4, Mélanie Gérault 
> wrote:
>>
>> Hi,
>>
>> I am wondering if anyone has ever implemented/used internal boundary 
>> conditions in deal.II. I need to impose displacements inside of a domain. I 
>> am assuming that it is feasible with the code, but please let me know if I 
>> am wrong.
>>
>> And in case I need to do it from scratch, I would also appreciate any 
>> suggestion you may have.
>>
>> Thanks a lot!
>>
>> Mélanie
>>
>

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[deal.II] Re: Specifying internal "boundary" conditions

[Bruno Turcksin]

Mélanie,

I am not sure I understand exactly what you want to do but often people who 
want internal boundary conditions, really just want to impose some 
constraints to a few dofs. This can be done using AffineConstraints 
. I 
am sure that you have seen it in the tutorials where it is used to 
constrain hanging nodes and to impose Dirichlet boundary condition. 
Basically, you can create one yourself to impose any constraint you want on 
any dofs.

I hope this help.

Bruno

On Wednesday, September 18, 2019 at 11:34:12 AM UTC-4, Mélanie Gérault 
wrote:
>
> Hi,
>
> I am wondering if anyone has ever implemented/used internal boundary 
> conditions in deal.II. I need to impose displacements inside of a domain. I 
> am assuming that it is feasible with the code, but please let me know if I 
> am wrong.
>
> And in case I need to do it from scratch, I would also appreciate any 
> suggestion you may have.
>
> Thanks a lot!
>
> Mélanie
>

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