# [Gmsh] uniform mesh refinement

**Jaensson, N.O.**
n.o.jaensson at tue.nl

*Sat Feb 22 12:01:56 CET 2014*

Dear Gmsh users,
I use Gmsh to generate quite simple 2nd-order 2D meshes, where one of
the boundaries is part of a circle. I would like to perform a mesh
convergence study of my FEM code, so I would like to be able to start
with a coarse mesh, which is subsequently uniformly refined a number of
times. If I load my .geo file into the GUI, I generate the coarsest mesh
by subsequently clicking "2D" in the "Mesh" section, and then "Set order
2", this aligns the midpoints of the quadratic elements nicely on the
circle. If I now click "Refine by splitting", a first order, refined
mesh is created. Clicking "set order 2", converts this into a second
order mesh where the midpoints of the quadratic elements align nicely
with the circle again. The problem is that I have no idea how to do this
using the command line, which I mainly use to generate meshes from
within the FEM code.
I am able to uniformly refine my mesh using the command line, by
following the suggestions in this thread:
http://www.geuz.org/pipermail/gmsh/2013/008004.html
However, the midpoints of the quadratic elements on the boundary are
just inserted between the existing nodes, and not on the circle. I guess
since the .msh file is used, the geometric information is lost, and new
nodes are just inserted between the existing nodes.
Since the GUI is able to do this, I expect that it is also possible from
the command line. Any help would be much appreciated!
Kind regards,
Nick