> On 26 May 2016, at 21:50, Karl Kästner <[email protected]> wrote:
>
> Hello,
>
> I want to vary the element size over a surface. More specifically I want to
> geometrically increase the element size with increasing distance from the
> boundary. I tried to use the boundary layer option but this did not work, as
> the surface shape is nontrivial and the edge length has also to vary along
> the boundary.
>
> Therefore I first generate an initial mesh, then compute the local element
> size at the interior points of the initial mesh, add the interior points of
> the initial mesh to the geometry file and finally generate a second mesh.
>
> Unfortunately the points of the first mesh are also vertices of the second
> mesh, thus the element size of the second mesh cannot be lower than that of
> the first mesh. I tried to add the points to an attractor field, but gmsh
> displayed following warning and crashes:
>
> Error : Wrong mesh element size lc = 0 (lcmin = 0, lcmax = 1e+22)
>
(the attractor returns distances, which can here be equal to zero when you are
on the points)
Replace everything after
Plane Surface(1) = {1};
in your file with this:
// field 1 computes the distance to your boundary
Field[1] = Attractor;
Field[1].NNodesByEdge = 100;
Field[1].EdgesList = {1:32};
// field 2 processes this distance to create a size field from 0.01 to 0.1
Field[2] = Threshold;
Field[2].IField = 1;
Field[2].LcMin = 0.01;
Field[2].LcMax = 0.1;
Field[2].DistMin = 0.02;
Field[2].DistMax = 0.5;
Background Field = 2;
// don't extend the size field from the boundary
Mesh.CharacteristicLengthExtendFromBoundary = 0;
which will do what you want.
> Attached a trivial example reproducing the behaviour. Any help is appreciated.
>
> Kind regards,
>
> --
> Karl Kästner
> ------------
> Phd Student at Wageningen University & Research centre
> Hydrology and Quantitative Water Management Group
> Droevendaalsesteeg 3, Lumen building, 6708 PB Wageningen, The Netherlands
> Phone: +31617876970 (Netherlands) +491627351075 (Germany)
> Mail: [email protected]
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--
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine
Tetrahedron V, July 4-5 2016: http://tetrahedron.montefiore.ulg.ac.be
Free software: http://gmsh.info | http://getdp.info | http://onelab.info
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