'Set' of GridFunction do not work correctly for surface mesh.

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1

Hi,

When I set a grid function defined on a surface, the results seem wrong. See the following code and output.

When I set the parameter to BND, the values of h_n are still all zeros.

[code]from ngsolve import *
from netgen.csg import *
from netgen.meshing import MeshingStep

from ngsolve.webgui import Draw

geo = CSGeometry()
sphere = Sphere(Pnt(0, 0, 0), 1).bc(‘inner’)
left = Plane(Pnt(0.75, 0, 0), Vec(-1, 0, 0))
fsphere = sphere*left

geo.AddSurface(sphere, fsphere)
geo.NameEdge(sphere, fsphere, ‘boundary’)
mesh = Mesh(geo.GenerateMesh(maxh=0.3))

Draw(mesh)

print_vec = lambda u: print([_ for _ in u.vec.data])

V_H = H1(mesh)
print(V_H.FreeDofs())

h = CoefficientFunction(1)
h_n = GridFunction(V_H)

h_n.Set(h)
print_vec(h_n)

h_n.Set(h, BND)
print_vec(h_n)

h_n.Set(h, BBND)
print_vec(h_n)[/code]

0: 1111111111111111111111111111 [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0] [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0] [1.0, 1.0, 1.0, 1.0, 0.9999999999999999, 1.0, 1.0, 1.0, 1.0, 0.9999999999999998, 1.0, 0.9999999999999999, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]

2

Hi,

to set a function on the whole boundary, which is not marked explicitly as Dirichlet boundary, you have to use the syntax

h_n.Set(h, definedon=mesh.Boundaries(".*"))

When setting explicitly the whole boundary as Dirichlet boundary then the code works

V_H = H1(mesh, dirichlet=".*")
...
h_n.Set(h, BND)

Best,
Michael

3

Thanks, Michael.

Best wishes,
Zongze Yang