Read VTK file of an old dolfin 2019's solution

dolfinx
1

Hello, I’m trying to read a VTK file into dolfinx. In this file I’ve defined a velocity field c which I’ll use in the bilinear form :

a = fem.form(c*inner(grad(u),grad(v))*dx)

This VTK file was generated with dolfin 2019 as a solution.

Dolfinx: 0.3.1.0

2

Save the function in xdmf format ( XDMFFile, use write_checkpoint rather than write to ensure the details of the FEM is preserved). Then it may be easier to read the xdmf file from dolfinx.

Disclaimer: I haven’t tried it myself, so I’m not certain if the file formats are completely compatible.

3

In DOLFINx, we do not have any way of reading in data yet. This is work in progress.

4

Thank you for your tips and help dparsons and dokken.

5

I’m trying to recreate the field I created in dolfin.
Since I’m new in dolfinx I’ve being having some troubles. My goal is to create a subsection with some markers.
My problem is that on side I’ve dof indices and on the other cells indices.

tau.x.array[cells] = np.full(num_cells_ref,tau_value)

It’s probably something really easy to fix, but I’m not really familiar with all dolfinx functions.
Hole code:

import dolfinx
from mpi4py import MPI
import dolfinx.io
import ufl
import numpy as np

point = [.7, 0.55,0]


msh = dolfinx.mesh.create_unit_square(MPI.COMM_WORLD, 4, 4)
tdim = msh.topology.dim

V = dolfinx.fem.FunctionSpace(msh,('CG',1))
x = V.tabulate_dof_coordinates()

def marker1(x): return x[0] <= 0.5+1e-7


indices1 = dolfinx.mesh.locate_entities(msh, 2, marker1)

num_cells = msh.topology.index_map(tdim).size_local + \
            msh.topology.index_map(tdim).num_ghosts
            
cell_marker = np.zeros(num_cells, dtype=np.int32)
cell_marker[indices1] = 1
cell_tag = dolfinx.mesh.meshtags(msh, dim=tdim, indices=np.arange(num_cells),
                                         values=cell_marker)


tau = dolfinx.fem.Function(V)
tau.x.array[:] = 0

cells=cell_tag.indices[cell_tag.values==1]
num_cells_ref= len(cells)
tau_value=50

tau.x.array[cells] = np.full(num_cells_ref,tau_value)
6

this did the trick:

dof=dolfinx.fem.locate_dofs_topological(V,tdim,cells)