[petsc-users] PetscFEIntegrateBdResidual_Basic
Matthew Knepley
knepley at gmail.com
Tue Nov 21 05:32:23 CST 2017
On Mon, Nov 20, 2017 at 7:19 PM, David Fuentes <fuentesdt at gmail.com> wrote:
> Sorry, If I call this AddBoundary Twice with different markers/ids, the
> bcFunc seems to be applied to set values for DM_BC_ESSENTIAL not
> DM_BC_NATURAL?
>
> Can I call ierr = PetscDSSetBdResidual(prob, 0, f0_bd_u, f1_bd_zero)
> twice to set the f0 functions different for each boundary ?
>
Okay, this is the problem I was citing before. AddBoundary() does take
natural conditions, but it just ignores the inhomogeneous ones, which are
properly
integrated in the weak form. However, DS only takes a single pointfunction
and integrates over the whole boundary. Thus your fix. I will get this
fixed, but
since it entails some programming, it might take me a while. Sorry about
that.
Thanks,
Matt
>
> /*@C
> PetscDSAddBoundary - Add a boundary condition to the model
>
> Input Parameters:
> + ds - The PetscDS object
> . type - The type of condition, e.g. DM_BC_ESSENTIAL/DM_BC_ESSENTIAL_FIELD
> (Dirichlet), or DM_BC_NATURAL (Neumann)
> . name - The BC name
> . labelname - The label defining constrained points
> . field - The field to constrain
> . numcomps - The number of constrained field components
> . comps - An array of constrained component numbers
> . bcFunc - A pointwise function giving boundary values
> . numids - The number of DMLabel ids for constrained points
> . ids - An array of ids for constrained points
> - ctx - An optional user context for bcFunc
>
> Options Database Keys:
> + -bc_<boundary name> <num> - Overrides the boundary ids
> - -bc_<boundary name>_comp <num> - Overrides the boundary components
>
> Level: developer
>
> .seealso: PetscDSGetBoundary()
> @*/
>
> On Mon, Nov 20, 2017 at 11:33 AM, David Fuentes <fuentesdt at gmail.com>
> wrote:
>
>> Thanks! will give that a try!
>> df
>>
>> On Mon, Nov 20, 2017 at 11:23 AM, Matthew Knepley <knepley at gmail.com>
>> wrote:
>>
>>> On Mon, Nov 20, 2017 at 12:20 PM, David Fuentes <fuentesdt at gmail.com>
>>> wrote:
>>>
>>>> Thanks for the quick reply. Indeed it does work like this. I have added
>>>> a location dependence on the boundary to differentiate the two. However,
>>>> when my mesh moves then the BC will be applied incorrectly.
>>>>
>>>
>>> I don't think you should have to do that. You can call AddBoundary
>>> twice. Once with a function with the first branch and marker value 3, and
>>> the next with the second branch and marker value 2. Does
>>> that make sense?
>>>
>>> Thanks,
>>>
>>> Matt
>>>
>>>> *// PetscFEIntegrateBdResidual_Basic DMPlexComputeBdResidual_Internal*
>>>>
>>>>
>>>> *static* *void** f0_bd_u(PetscInt dim, PetscInt Nf, PetscInt NfAux,*
>>>>
>>>> *const** PetscInt uOff[], **const** PetscInt
>>>> uOff_x[], **const** PetscScalar u[], **const** PetscScalar u_t[], *
>>>> *const** PetscScalar u_x[],*
>>>>
>>>> *const** PetscInt aOff[], **const** PetscInt
>>>> aOff_x[], **const** PetscScalar a[], **const** PetscScalar a_t[], *
>>>> *const** PetscScalar a_x[],*
>>>>
>>>> * PetscReal t, **const** PetscReal x[], **const**
>>>> PetscReal n[], PetscInt numConstants, **const** PetscScalar
>>>> constants[], PetscScalar f0[])*
>>>>
>>>> *{ *
>>>>
>>>> * PetscInt d;*
>>>>
>>>> *double** radius = **0.0**;*
>>>>
>>>> *const* *double** zthresh = (**3.** - **4.5**/**2.**)***.01**; **//
>>>> [m]*
>>>>
>>>> *for** (d = **0**; d < **2**; ++d) radius += x[d]*x[d];*
>>>>
>>>> * radius = sqrt(radius); *
>>>>
>>>> *if** ( radius > **.001**/**2.** ) *
>>>>
>>>> * {f0[**0**] = constants[**2**] * u[**0**];}*
>>>>
>>>> *else*
>>>>
>>>> * {*
>>>>
>>>> * f0[**0**] = -constants[**3**] ; *
>>>>
>>>> * }*
>>>>
>>>> *} *
>>>>
>>>>
>>>> On Mon, Nov 20, 2017 at 11:02 AM, Matthew Knepley <knepley at gmail.com>
>>>> wrote:
>>>>
>>>>> On Mon, Nov 20, 2017 at 11:46 AM, David Fuentes <fuentesdt at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> *Is there a way to pass the boundary set id to the function pointers
>>>>>> for the residual evaluation on the boundary ?*
>>>>>>
>>>>>> *https://bitbucket.org/petsc/petsc/src/d89bd21cf2b5366df29efb6006298d2bc22fb509/src/dm/dt/interface/dtfe.c?at=master&fileviewer=file-view-default#dtfe.c-4245
>>>>>> <https://bitbucket.org/petsc/petsc/src/d89bd21cf2b5366df29efb6006298d2bc22fb509/src/dm/dt/interface/dtfe.c?at=master&fileviewer=file-view-default#dtfe.c-4245>*
>>>>>>
>>>>>> *I want to pass the boundary condition/constraint ID (ids):
>>>>>> PetscErrorCode PetscDSAddBoundary(PetscDS ds, DMBoundaryConditionType type,
>>>>>> const char name[], const char labelname[], PetscInt field, PetscInt
>>>>>> numcomps, const PetscInt *comps, void (*bcFunc)(void), PetscInt numids,
>>>>>> const PetscInt *ids, void *ctx)*
>>>>>>
>>>>>> *to the functions for the residual evaluation on the boundary.*
>>>>>>
>>>>>>
>>>>>> *For example, I have two side sets in an exodus file. I want to
>>>>>> implement Neumann boundary conditions on side set = 2 and Mixed/Cauchy BC
>>>>>> on side set = 3. Or similarly use different*
>>>>>>
>>>>>> *gmsh BC tags for Neumann/Mixed BC.*
>>>>>>
>>>>> I am not completely against this, but let me respond with my rationale
>>>>> first. What I thought you would do, is call AddBoundary() twice. Once with
>>>>> the
>>>>> Neumann function and value 2, and once with the Cauchy function and
>>>>> value 3. Does that not work in your situation?
>>>>>
>>>>> Also, I am refectoring this right now because a DS object can only
>>>>> take a single boundary integral point function (which is a pain for
>>>>> inhomogeneous Neumann),
>>>>> so I welcome input.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Matt
>>>>>
>>>>> --
>>>>> 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.caam.rice.edu/~mk51/>
>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> 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.caam.rice.edu/~mk51/>
>>>
>>
>>
>
--
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.caam.rice.edu/~mk51/>
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