[Gmsh] 3d Delaunay Mesh

[Juan Sanchez]

Hi,

On Wed, Jun 17, 2020 at 10:54 AM Christophe Geuzaine <cgeuzaine at uliege.be>
wrote:

>
> Hi Juan,
>
> This is expected: to get a 3D mesh that satisfies the Delaunay criterion
> we would need to modify the surface mesh - this is something we try hard to
> avoid.
>


In TetGen, I started experimenting with using a background mesh from the
initial mesh generated from the PLC.  Specifying smaller edge lengths on
the nodes of the bad elements results in a greatly improved mesh.

For a simple cube experiment:
If I subdivided a tetrahedron into 4, using the the center of the
circumsphere as the common vertex:
    The sum of the volumes of the subdivided elements was 50% higher than
the actual volume of the cube.

Using the background mesh, where I specified smaller edge lengths at the
vertices of the bad elements,
    The sum of the volumes of the subdivided elements matched the volume of
the cube.

I will port this refinement strategy back to Gmsh when I have the
opportunity.

Regards,

Juan


>
> Christophe
>
>
> > On 14 Jun 2020, at 20:17, Juan Sanchez <juan.e.sanchez at gmail.com> wrote:
> >
> > Hello,
> >
> > I am having a hard time getting a 3d delaunay mesh, so that the
> circumcenters of the tetrahedra are inside the element.
> >
> > In my simulator, I am seeing that about 50% of the elements are not
> delaunay if:
> > Mesh.CharacteristicLengthExtendFromBoundary = 1;
> >
> > and about 90% are not Delaunay if:
> > Mesh.CharacteristicLengthExtendFromBoundary = 0;
> >
> > Is there a way to improve this when running the tool from the command
> line or with an option in the geo file?
> >
> > I am using:
> > /Applications/Gmsh.app/Contents/MacOS/gmsh -format msh2 -3  3dblock.geo
> >
> > with version 4.5.6 on macOS 10.14.6 (Mojave).
> >
> > Regards,
> >
> > Juan
> > <3dblock.geo>_______________________________________________
> > gmsh mailing list
> > gmsh at onelab.info
> > http://onelab.info/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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