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
On Wednesday, 5 August 2020 20:36:09 UTC-4, yuesu jin wrote:
>
> 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
>
>
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