Anders Logg wrote:
> On Tue, Apr 01, 2008 at 02:32:17PM +0200, Murtazo Nazarov wrote:
>
>> Anders Logg wrote:
>>
>>> On Mon, Mar 31, 2008 at 07:15:23PM +0200, Murtazo Nazarov wrote:
>>>
>>>
>>>> Anders Logg wrote:
>>>>
>>>>
>>>>> On Mon, Mar 31, 2008 at 03:52:57PM +0200, Murtazo Nazarov wrote:
>>>>>
>>>>>
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> I want to apply a boundary condition to the vertices on a boundary. For
>>>>>> that I define:
>>>>>>
>>>>>> // Sub domain for MyBC
>>>>>>
>>>>>> class MyBC_Boundary2D : public SubDomain
>>>>>> {
>>>>>> public:
>>>>>> bool inside(const real* p, bool on_boundary) const
>>>>>> {
>>>>>> return on_boundary && (p[0] < xmax - bmarg) && (p[0] > xmin +
>>>>>> bmarg);
>>>>>> }
>>>>>> };
>>>>>>
>>>>>> Then I initialize:
>>>>>> //-----------------------------------------------------------------------------
>>>>>>
>>>>>> void MyBC::init(SubDomain& sub_domain)
>>>>>> { ...
>>>>>> mesh.init(0);
>>>>>> sub_domains = new MeshFunction<uint>(mesh, 0);
>>>>>> ...}
>>>>>>
>>>>>>
>>>>>>
>>>>> Do you remember to set everything to 1 (number of subdomains) here?
>>>>>
>>>>>
>>>>>
>>>>>
>>>> Yes I do:
>>>>
>>>> // Mark everything as sub domain
>>>> 1
>>>> (*sub_domains) = 1;
>>>>
>>>>
>>>> // Mark the sub domain as sub domain
>>>> 0
>>>> sub_domain.mark(*sub_domains, 0);
>>>>
>>>> /murtazo
>>>>
>>>>
>>> Then I have no idea. You just need to dig into the code and see what
>>> goes wrong.
>>>
>>>
>>>
>> I think I found a mistake in Subdomain.mark(). The thing is bool
>> on_boundary should be defined
>> inside the loop for computing subdomain marker:
>>
>> // Always false when not marking
>> facets
>>
>>
>> //bool on_boundary =
>> false;
>>
>>
>>
>> // Compute sub domain
>> markers
>>
>>
>> for (MeshEntityIterator entity(mesh, dim); !entity.end(); ++entity)
>> {
>> bool on_boundary = false;
>> ...
>> }
>>
>> Otherwise, if you want to apply a boundary condition on vertices, it
>> becomes always
>> true after once meeting a vertex on the boundary.
>>
>>
>> It solved problem for me.
>>
>
> I'm not sure. If you are marking vertices, then they will never be on
> the boundary, unless you are doing this for a 1-dimensional mesh
> (which typically has just 2 boundary vertices). Only *facets* will
> ever be marked as being on the boundary, so for a 2-dimensional mesh,
> edges on the boundary will be marked as being on the boundary and for
> a 3-dimensional mesh, faces on the boundary will be marked as being on
> the boundary.
>
>
With the change I wrote I was able to mark vertices. Because,
if I mark facets or faces, I miss some nodes in the boundary
of the subdomain where I am applying my bc. That destroys
the solution. Now, I apply my boundary only for vertices
I need, and I do not miss any nodes. It work perfectly with
the slip BC.
/murtazo
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