libmesh-users

[Libmesh-users] building sphere using tetrahedral elements

[Ramakrishnan T. <thi...@gm...>]

Dear libmesh users,

I want to create sphere with tetrahedral elements. I came across this
function MeshTools::Generation::build_square. But this function supports
only HEX8/27 for 3D.  Is there any other functions in libmesh that I could
use to generate sphere with tetrahedral elements?

Thanks in advance.

-- 
Regards
Ramakrishnan T.

Re: [Libmesh-users] building sphere using tetrahedral elements

[John P. <jwp...@gm...>]

On Thu, Jan 16, 2020 at 1:21 AM Ramakrishnan Thirumalaisamy <
thi...@gm...> wrote:

> Dear libmesh users,
>
> I want to create sphere with tetrahedral elements. I came across this
> function MeshTools::Generation::build_square. But this function supports
> only HEX8/27 for 3D.  Is there any other functions in libmesh that I could
> use to generate sphere with tetrahedral elements?
>

Hi Ramakrishnan,

Your email mentions both spheres and build_square, but I'm assuming what
you're really after is spheres. The implementation doesn't currently exist,
but you could do something similar to what's currently done in the
build_cube() case when Tets are selected. That is, first a mesh of
hexahedra is created and then each hex is split into IIRC 24 tets. This
isn't the most economical splitting but it is very "symmetric" and
therefore easy to make the split elements line up consistently. This
splitting also introduces new mid-face nodes, which could be "snapped" to
the sphere surface as necessary.

Another option would be to configure/build libmesh with the
--disable-strict-lgpl option and then use the libmesh Tetgen interfaces to
create a Delaunay mesh of the sphere. If you end up implementing either of
those, it would be great if you could contribute them back as either
library code or possibly an augmented miscellaneous_ex6.

Note that libmesh also supports reading several different mesh file
formats, so if you generate a sphere mesh in e.g. Gmsh, you would be able
to read it in without doing any major programming yourself...

-- 
John

Re: [Libmesh-users] building sphere using tetrahedral elements

[Ramakrishnan T. <thi...@gm...>]

Thank you. Sorry for the typo. It should be build_sphere instead of
build_square.

Yes. I already created sphere using gmsh and did my numerical experiment.
But i do not want to keep the mesh files in the remote repository. So I was
looking to circumvent this by creating sphere using libmesh.

If I could implement either of your suggestions, I will let you know.

On Thu, 16 Jan, 2020, 8:26 AM John Peterson, <jwp...@gm...> wrote:

>
>
> On Thu, Jan 16, 2020 at 1:21 AM Ramakrishnan Thirumalaisamy <
> thi...@gm...> wrote:
>
>> Dear libmesh users,
>>
>> I want to create sphere with tetrahedral elements. I came across this
>> function MeshTools::Generation::build_square. But this function supports
>> only HEX8/27 for 3D.  Is there any other functions in libmesh that I could
>> use to generate sphere with tetrahedral elements?
>>
>
> Hi Ramakrishnan,
>
> Your email mentions both spheres and build_square, but I'm assuming what
> you're really after is spheres. The implementation doesn't currently exist,
> but you could do something similar to what's currently done in the
> build_cube() case when Tets are selected. That is, first a mesh of
> hexahedra is created and then each hex is split into IIRC 24 tets. This
> isn't the most economical splitting but it is very "symmetric" and
> therefore easy to make the split elements line up consistently. This
> splitting also introduces new mid-face nodes, which could be "snapped" to
> the sphere surface as necessary.
>
> Another option would be to configure/build libmesh with the
> --disable-strict-lgpl option and then use the libmesh Tetgen interfaces to
> create a Delaunay mesh of the sphere. If you end up implementing either of
> those, it would be great if you could contribute them back as either
> library code or possibly an augmented miscellaneous_ex6.
>
> Note that libmesh also supports reading several different mesh file
> formats, so if you generate a sphere mesh in e.g. Gmsh, you would be able
> to read it in without doing any major programming yourself...
>
> --
> John
>

Re: [Libmesh-users] building sphere using tetrahedral elements

[<ed...@op...>]

>> 
>> 
>> On Thu, Jan 16, 2020 at 1:21 AM Ramakrishnan Thirumalaisamy <
>> thi...@gm...> wrote:
>> 
>>> Dear libmesh users,
>>> 
>>> I want to create sphere with tetrahedral elements. I came across this
>>> function MeshTools::Generation::build_square. But this function 
>>> supports
>>> only HEX8/27 for 3D.  Is there any other functions in libmesh that I 
>>> could
>>> use to generate sphere with tetrahedral elements?
>>> 
>> 
>> Hi Ramakrishnan,
>> 
>> Your email mentions both spheres and build_square, but I'm assuming 
>> what
>> you're really after is spheres. The implementation doesn't currently 
>> exist,
>> but you could do something similar to what's currently done in the
>> build_cube() case when Tets are selected. That is, first a mesh of
>> hexahedra is created and then each hex is split into IIRC 24 tets. 
>> This
>> isn't the most economical splitting but it is very "symmetric" and
>> therefore easy to make the split elements line up consistently. This
>> splitting also introduces new mid-face nodes, which could be "snapped" 
>> to
>> the sphere surface as necessary.
>> 
>> Another option would be to configure/build libmesh with the
>> --disable-strict-lgpl option and then use the libmesh Tetgen 
>> interfaces to
>> create a Delaunay mesh of the sphere. If you end up implementing 
>> either of
>> those, it would be great if you could contribute them back as either
>> library code or possibly an augmented miscellaneous_ex6.
>> 
>> Note that libmesh also supports reading several different mesh file
>> formats, so if you generate a sphere mesh in e.g. Gmsh, you would be 
>> able
>> to read it in without doing any major programming yourself...
>> 
>> --
>> John
>> 
> 
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> Libmesh-users mailing list
> Lib...@li...
> https://lists.sourceforge.net/lists/listinfo/libmesh-users

On 2020-01-16 17:33, Ramakrishnan Thirumalaisamy wrote:
> Thank you. Sorry for the typo. It should be build_sphere instead of
> build_square.
> 
> Yes. I already created sphere using gmsh and did my numerical 
> experiment.
> But i do not want to keep the mesh files in the remote repository. So I 
> was
> looking to circumvent this by creating sphere using libmesh.
> 
> If I could implement either of your suggestions, I will let you know.
> 
> On Thu, 16 Jan, 2020, 8:26 AM John Peterson, <jwp...@gm...> 
> wrote:
> 

Did you know that you can have a Gmsh script instead of a .msh (or 
another type of) file? (my 2 cents).

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