How to preserve stress field when deforming the mesh using ALE.move()

[dokken]

@Mohsen

gradu.interpolate(grad(u))

You need to use dolfinx.fem.Expression in the interpolation, see

How to write stresses to a xdmf file?

You should use dolfinx.fem.Expression to interpolate the stress into a suitable function space (DG of some order) and use dolfinx.io.VTXWriter to write it to file preserving the function space. You can see how B is computed in Electromagnetics example — FEniCSx tutorial E.g. W = VectorFunctionSpace(mesh, ("DG", 0)) B = Function(W) B_expr = Expression(as_vector((A_z.dx(1), -A_z.dx(0))), W.element.interpolation_points()) B.interpolate(B_expr) https://jsdokken.com/fenics22-tutorial/heat_eq.html…

and to move the mesh use

deformation_array = u.x.array.reshape((-1, mesh.geometry.dim))
    mesh.geometry.x[:, :mesh.geometry.dim] += deformation_array

as done in

Changing the shape in the surface normal directions

The simplest mesh deformation can be described as follows: import dolfinx from mpi4py import MPI from typing import List import numpy as np def deform_mesh(V, bcs: List[dolfinx.fem.DirichletBCMetaClass]): mesh = V.mesh u = dolfinx.fem.Function(V) dolfinx.fem.petsc.set_bc(u.vector, bcs) deformation_array = u.x.array.reshape((-1, mesh.geometry.dim)) mesh.geometry.x[:, :mesh.geometry.dim] += deformation_array mesh = dolfinx.mesh.create_unit_square(MPI.COMM_WORLD, 10, 10) …