How to apply a force load at a known node number

[dokken]

See for instance

Point Sources (Redux)

For dolfinx 0.8.0, simply use cmap = mesh.geometry.cmap. For dolfinx main branch (future 0.9.0), a few further changes in the call to dolfinx.cpp.geometry.determine_point_ownership are required due to Make standalone function for interpolation over non-matching meshes (… · FEniCS/dolfinx@ab79530 · GitHub. I copy the updated code below # Create a point source for Poisson problem # Author: Jørgen S. Dokken # SPDX-License-Identifier: MIT from mpi4py import MPI from petsc4py import PETSc import …

There are various other ways to do this as well, for instance with locate_dofs_topological or geometrical, see for instance How to apply a pointwise force using dolfinx - #6 by lyunfei1211
How to apply component wise dirichlet boundary condition on a point - #2 by dokken
or by looking at a map from global input index to dof:
How to apply a boundary condition to a range of DOFs? - #7 by dokken