Import a Function and a mesh, and derive corresponding vector-field

mesh
1

I am quite new with FEniCS so probably my problem is standard but I did not find a solution anywhere else. I am working on a tetrahedral mesh which is stored as a dolfin mesh file mesh.xml.gz. I have another file potential.xml.gz with the dof values derived from a “previous solution” and externally processed, defined on the mesh from a “CR” function space. These are scalar values defined at the barycenter of each facet of the tetrahedron. I would like to visualize the corresponding “gradient” as vector field defined in each Tet in Paraview. I am stuck with the following:

  1. How to import potential.xml.gz? Do I need to create a Function and map the corresponding values per dof? (something like vertex_to_dof_map)
  2. How to derive the corresponding gradient vector field?

Exporting the mesh with the vector field to ParaView is fine. Any help will be welcome

Thank you very much

2

Allright, so finally I found how to do it. It was not so complicated. I needed just to find the correct function spaces. This is my code to solve the problem

mesh = Mesh("mesh.xml.gz")
F = FunctionSpace(mesh,'CR',1)
f = Function(F,"potential.xml.gz")

G = VectorFunctionSpace(mesh,'DG',0)
g = Function(G)

vf = project(grad(f),g.function_space())

File("vector_field.pvd")<<vf

Thanks again

3

@Ra_Faniry

first of all hello,
I think i got the same problem as you but i don’t know how to fix it. Do you think you can help me?

Best regards