How to set initital values on specific boundaries in dolfin?

1

Hi everyone,

I want to specify initial values on specific boundaries of my 2D mesh in dolfin. The mesh is imported from gmsh with boundary and domain markers via:

mesh = Mesh()
mvc_domain = MeshValueCollection("size_t", mesh, 2)
with XDMFFile("mesh/gap_mesh.xdmf") as infile:
    infile.read(mesh)
    infile.read(mvc_domain)

mvc = MeshValueCollection("size_t", mesh, 1)
with XDMFFile("mesh/gap_mf.xdmf") as infile:
    infile.read(mvc, "Boundary")

domain = cpp.mesh.MeshFunctionSizet(mesh, mvc_domain)
boundaries = cpp.mesh.MeshFunctionSizet(mesh, mvc)

Markers for the boundaries are stored in boundaries and markers for the domain are stored in domain. I know that initial values can be specified for the domain with markers by using:

def initial_values(material1):
    W = FunctionSpace(mesh, "DG", 0)
    x = W.tabulate_dof_coordinates()
    E = Function(W, name="initial_values")
    for i in range(x.shape[0]):
        if domain.array()[i] == domain_marker:
            E.vector().vec().setValueLocal(i,material1)
    return E

My approach was to change if domain.array()[i] == domain_marker: to if boundaries.array()[i] == boundary_marker: which did not produce the desired results. Any ideas how to proceed?

2

What I would suggest is that you create a DirichletBC object over the current facets for a single material, and use bc.apply(E.vector()).

Edited from bc.assign to bc.apply

1 Like
3

Perfect, thank you!. For anyone using the same approach: I think it’s bc.apply(), instead of bc.assign().