[Gmsh] Help to use Gmsh for BEM

[Alexander Kalinin]

Hello Jose,

I also use Gmsh as a mesh generator for the 3D BEM method. I use Gmsh as:
(1) surface modeling tool and (2) 3D surface mesh generator.

I my software I also use discontinues elements in two ways: (1)
Geometrically BEM node is the same as mesh node, but functionally they are
the different nodes.  I use this approach when I treat the normals
direction in the corner. (2) BEM node geometrically shifted into the
element.

But I don't use Gmsh for such nodes generation. I working only with
resulting 3D mesh and use local coordinates bases. For example, when I use
the shifted nodes for each element I set the shifted BEM nodes local
coordinates as (0.75, 1.0, 1.0), (1.0, 0.75, 1.0), (1.0, 1.0, 0.75).

Sincerely,
Alexander Kalinin

On Sat, Sep 22, 2012 at 11:09 PM, José Jeferson Rêgo Silva <
jjregosilva at gmail.com> wrote:

>  Dear Sirs.
>
> We are trying to use *Gmsh* as a mesh generator for a 3D boundary element
> software (surface modeling).
> Do you have any experience in doing so?
>
> The purpose of our work is academic, for teaching and research, helping to
> use our BE software.
> We understand that for others purposes it will be necessary a different
> type of license.
>
> It seems that modeling surfaces with *Gmsh* could help.
> Our major difficulty is when dealing with adjacent elements that do not
> share the same functional nodes.
> The geometric nodes, however, are kept the same, naturally.
>
> For these cases, we are used to employ the so-called "discontinuous
> element" (also known as "non-conforming" element).
> An alternative is to use "double nodes", that is not our case.
>
> The idea of discontinuous element is to place the functional nodes inside
> the element, instead of on its boundary (edge).
> On the contrary of FEM, this do not affect BEM formulations.
>
> So, we would like to know if *Gmsh *has this capability of creating new
> nodes inside the elements, when necessary, accordingly to different types
> of connectivity between adjacent elements. Sometimes an surface element can
> share functional nodes with one (or more) of its adjacent elements, and do
> not share functional nodes with the others.
>
> It is not necessary *Gmsh* generate the coordinates for these new nodes.
> Our software can handle it.
> It is necessary, however, to number these new nodes and associate them to
> each element (keeping the same element orientation - ordering of their
> nodes), as it is already done for the others standard (geometric) nodes.
>
> Thanks in advance.
> Greetings.
>
> J. Jeferson Rêgo Silva
> Civil Engineering Department - UFPE
>
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