clear_spline_nodes param in FileMesh, FM Generator

This lets us choose to load an IsoGeometric Analysis mesh without spline
nodes and spline node constraints, whether for debugging purposes or to
experiment with solver behavior or just because libMesh doesn't
parallelize those constraints efficiently enough yet.

Refs idaholab#18768

framework/src/mesh/FileMesh.C

@@ -15,6 +15,7 @@
 #include "RestartableDataIO.h"
 
 #include "libmesh/exodusII_io.h"
+#include "libmesh/mesh_tools.h"
 #include "libmesh/nemesis_io.h"
 #include "libmesh/parallel_mesh.h"
 
@@ -25,6 +26,11 @@ FileMesh::validParams()
 {
   InputParameters params = MooseMesh::validParams();
   params.addRequiredParam<MeshFileName>("file", "The name of the mesh file to read");
+  params.addParam<bool>("clear_spline_nodes",
+                        false,
+                        "If clear_spline_nodes=true, IsoGeometric Analyis spline nodes "
+                        "and constraints are removed from an IGA mesh, after which only "
+                        "C^0 Rational-Bernstein-Bezier elements will remain.");
   params.addClassDescription("Read a mesh from a file.");
   return params;
 }
@@ -112,6 +118,9 @@ FileMesh::buildMesh()
       MooseUtils::checkFileReadable(_file_name);
       getMesh().read(_file_name);
 
+      if (getParam<bool>("clear_spline_nodes"))
+        MeshTools::clear_spline_nodes(getMesh());
+
       // we also read declared mesh meta data here if there is meta data file
       RestartableDataIO restartable(_app);
       std::string fname = _file_name + "/meta_data_mesh" + restartable.getRestartableDataExt();

framework/src/meshgenerators/FileMeshGenerator.C

@@ -15,6 +15,7 @@
 #include "libmesh/face_quad4.h"
 #include "libmesh/exodusII_io.h"
 #include "libmesh/mesh_communication.h"
+#include "libmesh/mesh_tools.h"
 
 registerMooseObject("MooseApp", FileMeshGenerator);
 
@@ -35,6 +36,11 @@ FileMeshGenerator::validParams()
                         false,
                         "True to skip partitioning, only after this mesh generator, "
                         "because the mesh was pre-split for example.");
+  params.addParam<bool>("clear_spline_nodes",
+                        false,
+                        "If clear_spline_nodes=true, IsoGeometric Analyis spline nodes "
+                        "and constraints are removed from an IGA mesh, after which only "
+                        "C^0 Rational-Bernstein-Bezier elements will remain.");
   params.addClassDescription("Read a mesh from a file.");
   return params;
 }
@@ -72,7 +78,12 @@ FileMeshGenerator::generate()
     else
     {
       if (mesh->processor_id() == 0)
+      {
         exreader->read(_file_name);
+
+        if (getParam<bool>("clear_spline_nodes"))
+          MeshTools::clear_spline_nodes(*mesh);
+      }
       MeshCommunication().broadcast(*mesh);
     }
     // Skip partitioning if the user requested it