fix(utils/meshGeneration): changed mesh format to gmsh 2.2

meshio writes vtk version 9 but mfem only supports up to version 4, so we changed to gmsh version 2.2 which is supported

utils/meshGeneration/generateMesh.py

@@ -12,7 +12,7 @@ def generate_spherical_mesh(radius=1, meshSize=0.1):
     return myMesh
 
 def write_mfem_mesh(meshData, filename):
-    meshio.write(filename, meshData, file_format='vtk')
+    meshio.write(filename, meshData, file_format='gmsh22')
 
 if __name__ == '__main__':
     parser = argparse.ArgumentParser(description='Generate a spherical mesh')
@@ -21,4 +21,4 @@ if __name__ == '__main__':
     args = parser.parse_args()
 
     meshData = generate_spherical_mesh(args.radius, args.meshSize)
-    write_mfem_mesh(meshData, 'sphere.vtk')
+    write_mfem_mesh(meshData, 'sphere.msh')