Failure in importing second-order mesh in legacy FEniCS

[dokken]

@yuki_y

FYI, I have also succeeded in loading the box.msh(with second-order mesh) in a Fenicsx script using gmshio.read_from_msh, and the problem can be solved without any issues. I want to stick with Fenics because there are some arc_length solvers available here, while Fenicsx doesn’t have them yet.

Legacy FEniCS does not have out of the box support for second order meshes. One would manually have to permute the topological entities when adding them through the use of dolfin.MeshEditor.
Some of this has been explained in: Generation of second-order triangular meshes in legacy FEniCS - #4 by dokken

Maybe what you need is implemented in DOLFINy? (dolfiny/src/dolfiny/continuation.py at 39ddc50e99e38235c2aac8c489605726fbee64df · fenics-dolfiny/dolfiny · GitHub, ref: file:///home/dokken/Downloads/fenics2022-tdc-zilian-2.pdf)