Hello, Below is a minimum working example showing that ufl.FacetArea can not be used with quadrilateral mesh. from mpi4py import MPI import numpy as np import dolfinx from dolfinx.fem.petsc import assemble_matrix import ufl # msh = dolfinx.mesh.create_rectangle(comm=MPI.COMM_WORLD, points=((0.0, …

Sorry, I did something wrong in my script. I confirm that the script in the above post works.

You can create a sub-mesh of the facets of the mesh, and use the h function on the submesh: dolfinx/python/dolfinx/mesh.py at b694be6e66f9043de039ebc18c166733d044409f · FEniCS/dolfinx · GitHub

Thank you for the answer, I understand the idea but I don’t know how to implement it. I tried: facets = dolfinx.mesh.locate_entities(msh, msh.geometry.dim - 1, lambda x: np.full_like(x[0], 1, dtype=np.int8)) submesh_facets, _, _, _ = dolfinx.mesh.create_submesh(msh, msh.geometry.dim-1, facets) Ve =…

Something like the following may help. Here I’ve used both the Mesh::h function as suggested by @dokken and an assembly of \int_\kappa \mathrm{d}\vec{x}, \kappa \in \mathcal{T}^h(\Omega), exploiting a degree 0 DG space. Both in this instance yield the same result; however, if you have a high order m…

Thank you Nate for your help. However I still have the error ValueError: Multiple domains found, making the choice of integration domain ambiguous. The issue is not really how to compute the facet areas but rather how to use in a form like ufl.dot(ufl.grad(u) * fa, ufl.grad(v)) * ufl.ds Here is t…

Hello, I still did not find any solution to my problem (basically computing something like ufl.dot(ufl.grad(u) * facet_area, ufl.grad(v)) * ufl.dS'). In the examples above, facet_area is defined as a function on submesh_facets then assembling the above expression fails because u and v are defined…

I think you should use entity_maps, see for instance Multiphysics: Solving PDEs on subdomains — FEniCS Workshop

Hi, I took me while but I understood how to use entity_maps. But now I can compute form_a corresponding to a = ufl.inner(ufl.grad(u) * fa, ufl.grad(v)) * ds in the example below. However, I don’t know how to compute form_b (see again in the example below) corresponding to b = ufl.inner(ufl.grad(u)…

ufl.FacetArea for quadrilaterals

General

dokken March 19, 2026, 9:17pm 9

What version of DOLFINx are you running? I cannot reproduce the error on my system. This error reminds me of before the support of codim-1 and codim-2 support, ref:

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ufl.FacetArea for quadrilaterals

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