Set up boundary id in gmsh

[yuesu jin]

Dear all,

  I want to set up one Dirchlet boundary condition and one Neumann boundary condition on a 2d  mesh, which is generated by gmsh. How can I set up the mesh file in order to tell dealii with the boundary id when I input the .msh file into dealii? Thanks!

Best regards,

--

Yuesu Jin,

Ph.D student,

University of Houston,

College of Natural Sciences and Mathematics,

Department of Earth and Atmospheric Sciences,
Houston, Texas 77204-5008


346-404-2062

[Bruno Blais]

The best way to proceed is to set the boundary conditions using Physical Entities in GMSH.

An example is always better. For example, the following GMSH code :

 lc = 2.0e-1;
 lf = 2.0e-1;
 RO=1;
 RI=0.25;
 
 Point(0) = {0, 0, 0, lc};
 Point(1) = {RO, 0, 0, lc};
 Point(2) = {0, -RO , 0, lc};
 Point(3) = {-RO, 0, 0, lc};
 Point(4) = {0, RO, 0, lc};
 
 Point(5) = {RI, 0, 0, lf};
 Point(6) = {0, -RI , 0, lf};
 Point(7) = {-RI, 0, 0, lf};
 Point(8) = {0, RI, 0, lf};
 
 Circle(1)={1,0,2};
 Circle(2)={2,0,3};
 Circle(3)={3,0,4};
 Circle(4)={4,0,1};
 
 Circle(5)={5,0,6};
 Circle(6)={6,0,7};
 Circle(7)={7,0,8};
 Circle(8)={8,0,5};
 
 Line Loop(1) = {1,2,3,4};
 Line Loop(2) = {5,6,7,8};
 
 Plane Surface(1) = {1,2} ;
 //Transfinite Surface{1}={1,2,3,4};
 Recombine Surface{1,2};
 
 // Creates a physical entity 1 (i.e. for a BC)
 //Physical Point(1) = {1,2} ;
 Physical Line(0)={1,2,3,4};
 Physical Line(1)={5,6,7,8};
 
 Physical Surface(0) = {1};

Produces a 2D mesh of a single surface with id 0. It has two boundary conditions (0) and (1). One on the outer circle and the other on the inner circle. We use it to simulate a Taylor-Couette flow.

If you wanted to use a 3D mesh, then you would make a Physical Volume(0) and you would use the Physical Surface for the boundary conditions

Best

Bruno

[yuesu jin]

Dear Bruno,

  Thank you very much!!! This solved my problem. This is very helpful! 

Best regards,

Yuesu

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[Bruno Blais]

The pleasure is mine.

You will find that people the deal.II community are very helpfull :)!

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