# [Gmsh] Reflect mesh

Christophe Geuzaine cgeuzaine at ulg.ac.be
Mon Feb 5 14:32:45 CET 2007

```Amit.Itagi at seagate.com wrote:
> Hi,
>
> Consider the following surface geometry ( I am working on a more involved
> geometry. However, to explain the problem I am facing, the following
> geometry is good enough.)
>
> - - - - - - - - - -           - - - - - - - - - -
> |                     |         |                       |
> |                     |_ _ _|                       |
> |                                                       |
> |                                                       |
> - - - - - - - - - - - - - - - - - - - - - - - - -
>
> I need to apply a boundary condition connecting the left boundary to the
> right ( eg: Periodic boundary condition). After searching the mailing list,
> I found that the two boundaries need to have one to one correspondence in
> terms of the points/edges. One way to do this is to make the two surfaces
> transfinite. However, in my problem, the points at the top and the points
> at the bottom have different characteristic length. Thus, when I mesh the
> geometry with triangles, I have a gradient in the triangle size from top to
> bottom. Thus, I end up with skewed/divided triangles near the boundary (
> Ideally, I would like the transfinite points to be spaced with the same
> progression as the characterictic size of the triangles).  My questions
> follow:
>
> 1) What progression does the interpolation of characteristic length  follow
> from top to bottom ? If I know this, I can use the same progression for the
> transfinite points.

Linear interpolation. (But we actually never implemented linear
interpolation for 1D transfinite grids ;-)... I've added this to our
TODO list.)

>
> 2) Another way is, not to make the lines transfinite, and hope to use the
> mirror symmetry of the problem. I know that I can create the geometry using
> a symmetry transformation. But is there a way to mesh one half and use the
> mirror symmetry to generate the mesh for the mirrored half ?
>

Unfortunately, that's not implemented in the current version. We are

> Thanks
>
> Rgds,
> Amit
>
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> 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

```