# [Gmsh] Parameters for mesh refinement in 3D

Christophe Geuzaine cgeuzaine at uliege.be
Fri Jul 27 08:27:52 CEST 2018

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> On 13 Jul 2018, at 16:46, Octavio Castillo Reyes <ocastilloreyes at gmail.com> wrote:
>
> Dear all,
>
> I'm writing to you because I need some tips/advices for mesh refinement. Given a simple model like the one attached to this mail, If the spacing for material 1 is d1 = 300 m, and for material 2 it is d2 = 220 m. How to define the spacing for points p1, p2, p3, p4, p5, p6? How to refine near points p7, p8, ...., p14? For these points, I want a refinement equal to d1/20 and that extends up to 80 m from each point.
>
> I have already done experiments but it is not clear to me how to handle the attractor option, namely I don't know if following lines are correct:
>
> d1 = 300;
> d2 = 220;
>
> Field[1] = Attractor;
> Field[1].NodesList = {7:14};
> Field[2] = Threshold;
> Field[2].IField = 1;
> Field[2].LcMin = d1/20;
> Field[2].LcMax = ds;
> Field[2].DistMin = d1/20;
> Field[2].DistMax = 80;
> Field[3] = Min;
> Field[3].FieldsList = {2};
> Background Field = 3;

Looks ok (the Min field is not necessary) ; it will work both in 2D and 3D.

Also make sure to add Mesh.CharacteristicLengthExtendFromBoundary = 0 so that this automatic interpolation is not applied.

CG

>
> Characteristic Length {1, 2, 3, 6} = d1;
> Characteristic Length {4, 5} = d2;
>
> Finally, I don't know if this options are valid for a 3D case.
>
> Thank you for your time and support.
>
> Best regards
>
> <Mesh_example.pdf>_______________________________________________
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—
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine

Free software: http://gmsh.info | http://getdp.info | http://onelab.info

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