Boundary condition for a wild object

[dokken]

As all of them are lines you can use subdomains to mark a mesh function, as shown here:

Define boundaries for intersection of two cylinders

Please consider the following: class cyl1(SubDomain): def inside(self, x, on_boundary): return on_boundary and np.isclose(np.sqrt((x[0]-c1)**2+(x[1]-c1)**2), 0.075, rtol=3e-2) class cyl2(SubDomain): def inside(self, x, on_boundary): return on_boundary and np.isclose(np.sqrt((x[0]-c2)**2+(x[1]-c1)**2), 0.075, rtol=3e-2) mf = MeshFunction("size_t", mesh, 2, 0) cyl1().mark(mf, 2) cyl2().mark(mf, 3) File("mf.pvd") << mf Then you can use the DirichletBC interface to enfo…