that would be great if someone could give me a hint on the following. I need to assign boundary conditions to the faces of my mesh, exactly what is done by Mesh->Edit Boundary Condition… in NGSolve GUI, but from a script, because I will have to do it many times and there are many faces.
I am trying to do it with a python script, a simplified version of which looks like this:
from netgen.meshing import *
from netgen.csg import *
from ngsolve import *
geometry = CSGeometry()
bigball = Sphere(Pnt(0.0, 0.0, 0.0), 100.0);
smallball = Sphere(Pnt(0.0, 0.0, 0.0), 20.0);
vac = bigball - smallball
ngmesh = geometry.GenerateMesh()
ngmesh.Export(‘.’, ‘Elmer Format’)
mesh = Mesh(ngmesh)
This script can be executed, but it will not assign boundary 2 to face 1 and boundary 1 to face 2, as I would like it to. Instead, it will assign:
face – boundary
1 – 1
2 – 2
3 – 2
4 – 1
So it simply adds non-existing faces 3 and 4 instead of changing the assignments for faces 1 and 2. Does anybody know how to make netgen change boundary numbers assigned to faces instead of adding new faces?
Or any other way to change these assignments automatically? I thought about replacing the boundary numbers in the mesh.boundary file afterwards, but netgen only assigns boundary numbers from 1 to 22 and I have more faces, so I can’t identify faces by boundary numbers.