How to get facet diameter in 3D mesh

Dear Fenics community.

I am working on a variational formulation with a 3D mesh. In particular, I find myself calculating integrals on faces and accessing to local values like the MWE below.

from dolfin import *
mesh = UnitCubeMesh(1, 1, 1)
V = FunctionSpace(mesh, "DG", 0)
he = FacetArea(mesh)
w = TestFunction(V)
value = assemble(avg(he)*avg(w) * dS)

I thought FacetArea(mesh) would give me the diameter of the facet (triangles for this case). However, it gives me the areas of the faces. I would like to know if it is possible to define a symbolic function that evaluates to the facet diameter on each facet of the 3D mesh (similar to CellDiameter(mesh) in 2D).

Thanks in advance!

Hi @Jesus_Vellojin ,

I do not have the clear solution for your question, but the following code may be useful for you.

from fenics import *

mesh = UnitCubeMesh(10,10,10)
Bmesh = BoundaryMesh(mesh, 'exterior')
a = CellDiameter(Bmesh)