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GMSH 3D mesh generation

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Old   May 9, 2024, 04:47
Default GMSH 3D mesh generation
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sr
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Dear all,



I'm trying to generate a 3D mesh for an external CFD problem in gmsh. I have generated the domain shape and imported the .stp file of the body but I can't understand how to subtract this body from the volume domain (I want the mesh only outside of the body). Here you can find a simple example in which I want to create an external mesh around a sphere:


---------------------------------------

SetFactory('OpenCASCADE');

Point(1) = {1, -1, -1, 1.0};
Point(2) = {1, 1, -1, 1.0};
Point(3) = {-1, 1, -1, 1.0};
Point(4) = {-1, -1, 1, 1.0};
Point(5) = {1, -1, 1, 1.0};
Point(6) = {1, 1, 1, 1.0};
Point(7) = {-1, 1, 1, 1.0};
Point(8) = {-1, -1, -1, 1.0};
Line(1) = {7, 6};
Line(2) = {6, 5};
Line(3) = {5, 1};
Line(4) = {1, 8};
Line(5) = {8, 3};
Line(6) = {3, 7};
Line(7) = {7, 4};
Line(8) = {4, 8};
Line(9) = {4, 5};
Line(10) = {2, 1};
Line(11) = {2, 6};
Line(12) = {2, 3};
//+
Line Loop(1) = {6, 1, -11, 12};
Plane Surface(1) = {1};
Line Loop(2) = {11, 2, 3, -10};
Plane Surface(2) = {2};
Line Loop(3) = {2, -9, -7, 1};
Plane Surface(3) = {-3};
Line Loop(4) = {6, 7, 8, 5};
Plane Surface(4) = {-4};
Line Loop(5) = {8, -4, -3, -9};
Plane Surface(5) = {5};
Line Loop(6) = {10, 4, 5, -12};
Plane Surface(6) = {6};
//+
Merge "sphere.stp";
//+
Physical Surface(1) = {4, 3, 2, 6};
Physical Surface(2) = {1};
Physical Surface(3) = {5};
Physical Surface(4) = {7, 8};
//+
Surface Loop(2) = {6, 2, 1, 4, 3, 5};
Volume(2) = {2, 1};
----------------------------------------------

Does anyone know how to do it?


With kind regards,
Silvio
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Old   May 22, 2024, 02:43
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Gaurav Gupta
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Hii,
I guess you want to generate a 3D mesh for flow around a sphere. I am also trying to do the same but a structured one in gmsh. Having a tough time with that.

For subtracting the sphere from the domain, you can use the BooleanDifference command in gmsh. I am not sure how to use it with a imported model but if its a volume the boolean operation can be done.

Hope it helps !

Gaurav.
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