How to apply a load on a single point or a node

[dokken]

See for instance:

How to define different materials / importet 3D geometry (gmsh)

Following Dolfinx discontinous expression, this code can be modified for the syntax in dolfin as follows: import dolfin mesh = dolfin.UnitCubeMesh(9, 9, 9) V = dolfin.FunctionSpace(mesh, "DG", 0) v = dolfin.Function(V) x = V.tabulate_dof_coordinates() mf = dolfin.MeshFunction("size_t", mesh, mesh.topology().dim()) class Obstacle(dolfin.SubDomain): def inside(self, x, on_boundary): return (dolfin.between(x[1], (0.2, 0.7)) and dolfin.between(x[0], (0.3, 0.7))) Obstacl…

Or
https://fenicsproject.org/olddocs/dolfin/latest/python/demos/subdomains-poisson/documentation.html?highlight=subdomain