[Gmsh] Boundary layers in gmsh?

[David Colignon]

Hi Eric,

there is the "Boundary{}" command :

http://www.geuz.org/gmsh/doc/texinfo/gmsh.html#Transformations

Boundary { transform-list }
     (Not a transformation per-se.) Returns the boundary of the elementary entities in transform-list.

with

      transform-list:
        Point | Line | Surface | Volume { expression-list };

Regards,

Dave

-- 
David Colignon, Ph.D.
Collaborateur Logistique du F.R.S.-FNRS
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On 26/02/10 08:39, Eric Nutsch wrote:
> Christophe,
>
>
> It appears that the surface loop method to the boundary layer will
> work in most all cases, but I may have found a more efficient way.
>
> The BL extrude command returns a volume number as well. If it were
> possible to take the farfield and preform a boolean operation with the
> BL volumes, it would make the process very simple even for complex
> BLs.
>
> I attempted this for in your sphere example:
> Volume(1001) = {1002, 1,2,3,4,5,6,7,8};
>   ,but gmsh replied with "Unknown surface loop 1"
>
> Is there any way to convert a volume (created via extrude for example)
> to be converted into a surface loop?
> Perhaps I am missing an important leap in the coding structure, but if
> it was possible it would be an extremely handy function.
>
> What are your thoughts?
>
>
> Thanks,
> Eric Nutsch
>
>
>
>
> On Wed, Feb 24, 2010 at 4:03 AM, Christophe Geuzaine
> <cgeuzaine at ulg.ac.be>  wrote:
>> On 24/02/10 11:26, julien hoessler wrote:
>>>
>>> Hi Eric,
>>> If it is a flat surface or if you know where the interface would be
>>> located you can just move your domain line/surface to the interface and
>>> extrude it towards the outside, but otherwise I can't seem to find a way
>>> to link the interface with the rest of the mesh
>>
>> Hi Guys - boundary layers are still a bit experimental, but the basics are
>> there to connect them with other geometrical entities. Attached are two
>> examples:
>>
>> * sphere_boundary_layer.geo shows how to connect volumes to boundary layer
>> faces ;
>>
>> * t1_boundary_layer_connection.geo shows how you can also connect things to
>> the lines or vertices created during the boundary layer generation.
>>
>> Retrieving the id numbers of the extruded entities can be done in a script
>> the usual way (list[] = Extrude...), but as usual this only gives access to
>> the ids of the "top" surface, the new volume and the "lateral" surfaces.
>>
>> To retrieve the ids of the new lines and the new points, you have at the
>> moment to resort to the GUI (in "Tools->Options->General->General" select
>> "Enable mouse hover over meshes" to see the numbers displayed at the bottom
>> of the graphical window).
>>
>> Hope this helps,
>>
>> Christophe
>>
>>> regards
>>> Julien
>>> On 24 Feb 2010, at 02:03, Eric Nutsch wrote:
>>>
>>>> Hi,
>>>>
>>>>
>>>> Has anyone successfully gotten an extruded boundary layer to interface
>>>> with a mesh?
>>>>
>>>>
>>>> Thanks,
>>>> Eric Nutsch
>>>>
>>>> _______________________________________________
>>>> gmsh mailing list
>>>> gmsh at geuz.org
>>>> http://www.geuz.org/mailman/listinfo/gmsh
>>>
>>> Julien Hoessler
>>> PhD Student
>>> Department of Aeronautics
>>> Imperial College London
>>>
>>> Phone: +44 (0) 20759 45042
>>> Email: julien.hoessler06 at imperial.ac.uk
>>>
>>>
>>> _______________________________________________
>>> gmsh mailing list
>>> gmsh at geuz.org
>>> http://www.geuz.org/mailman/listinfo/gmsh
>>>
>>>
>>
>>
>> --
>> Prof. Christophe Geuzaine
>> University of Liege, Electrical Engineering and Computer Science
>> http://www.montefiore.ulg.ac.be/~geuzaine
>>
>
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