[Gmsh] Issue with multiple fields ( attractor and thresholds)

DILASSER Guillaume Guillaume.DILASSER at cea.fr
Thu Apr 27 08:19:55 CEST 2017


The Background Field = <field_id> ; command is used to declare that field <field_id> should be used to set the local mesh size. Therefore, the result you get is perfectly normal : as you set field 4 to be used as background, all refinement information that should come from field 2 is simply never applied. To combine the effect of fields 2 and 4, use a Min field, like in Gmsh tutorial 10<http://gmsh.info/doc/texinfo/gmsh.html#t10_002egeo>. By declaring field 5 that is the minimum of field 2 and 4 and then applying 5 as the background field, you will get the refinement of field 2 and 4 combined.

Faithfully Yours,

Guillaume DILASSER
Doctorant SACM / LEAS
CEA - Centre de Saclay - Bât.123 - PC 319c
91191 Gif sur Yvette Cedex - France -

guillaume.dilasser at cea.fr<mailto:guillaume.dilasser at cea.fr>

De : gmsh [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be] De la part de Prithivirajan V
Envoyé : mercredi 26 avril 2017 18:20
À : gmsh at geuz.org
Objet : [Gmsh] Issue with multiple fields ( attractor and thresholds)

Dear Gmsh users,

I am trying to create 3D volume mesh from .STL files that I have. In addition, I am trying to refine my 3D mesh locally around known points. I am using 2 sets of attractor /threshold to carry out differential refinements.However,  I am not able to carry out these two simultaneous refinements, I am only getting a refined mesh only at one of the locations.

Could you help me fix this - am I doing anything wrong ?

Also, could you make me understand what precisely the background field does ?

An excerpt from the code :

Merge "F:\Research\Work\Dream3D_v5.1_wrking\Meshfiles\Grain_1.stl";
Surface Loop(1)={1};
Physical Volume(1)={1};
Merge "F:\Research\Work\Dream3D_v5.1_wrking\Meshfiles\Grain_2.stl";
Surface Loop(2)={2};
Physical Volume(2)={2};
Merge "F:\Research\Work\Dream3D_v5.1_wrking\Meshfiles\Grain_3.stl";
Surface Loop(3)={3};
Physical Volume(3)={3};

Field[1] = Attractor;
Field[1].NodesList = {108706};
Field[2] = Threshold;
Field[2].IField = 1;
Field[2].LcMin = 0.75;
Field[2].LcMax = 3;
Field[2].DistMin = 15;
Field[2].DistMax = 30;

Field[3] = Attractor;
Field[3].NodesList = {90000,90001,90002,90003};
Field[4] = Threshold;
Field[4].IField = 3;
Field[4].LcMin = 1.5;
Field[4].LcMax = 3;
Field[4].DistMin = 3;
Field[4].DistMax = 7.5;

Background Field = 4;
Mesh.CharacteristicLengthExtendFromBoundary = 0;

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