Modifying gmsh input files

In this example we will use mooseherder’s input modifier to programmatically change variables in a gmsh .geo script.

We start by importing the packages we need for this example.

from pathlib import Path

# Pyvale imports
import pyvale.dataset as dataset
from pyvale.mooseherder import InputModifier

We are going to use a gmsh geo file that is for a 2D rectangular plate with a hole in the center which we retrieve from pyvale’s simulation library. We then use this to create an input modifier which has the correct comment string ‘//’ for gmsh and the required line terminator “;”.

gmsh_input = dataset.sim_case_gmsh_file_path(case_num=17)
gmsh_mod = InputModifier(gmsh_input, "//", ";")

Note that the input modifier class only looks for variables between specified sentinel characters in comment lines which starts with ‘_*’ and ends with ‘**’ . An example variable block can be found in the gmsh input file.

We then print the variables found in the gmsh input file to the console which are returned to us as a dictionary keyed by the variables string name in the file:

print(gmsh_mod.get_vars())
print()

We can update the variables in the input modifier using a dictionary keyed by the variable names we want to change and the values being what we want to change them to. We do not have to use numeric values for these we can use expressions in strings.

new_vars = {"plate_width": 150e-3, "plate_height": "plate_width + 100e-3"}
gmsh_mod.update_vars(new_vars)

Now we print the variables that are currently in the input modifier to check our modification worked.

print(gmsh_mod.get_vars())
print()

Finally we want to save the modified input file to disk so we can run it with gmsh. First we create the standard pyvale-output directory so we can save the file there. Then we save the gmsh input file to the directory with a suitable name. Have a look at the file in the directory to ensure our modifications have worked.

output_path = Path.cwd() / "pyvale-output"
if not output_path.is_dir():
    output_path.mkdir(parents=True, exist_ok=True)

gmsh_save = output_path/"gmsh-mod-vars.geo"
gmsh_mod.write_file(gmsh_save)