aprilnovak · MohamedElkamash · Apr 10, 2023 · Apr 11, 2023 · Apr 11, 2023 · Apr 11, 2023
diff --git a/framework/doc/content/source/meshgenerators/FlipSidesetGenerator.md b/framework/doc/content/source/meshgenerators/FlipSidesetGenerator.md
@@ -0,0 +1,14 @@
+# FlipSidesetGenerator
+
+!syntax description /Mesh/FlipSidesetGenerator
+
+## Overview
+
+The `FlipSidesetGenerator` object flips the normal of a sideset by changing the element the sideset is attached to. 
+The sideset can't be flipped if the original element it is attached to doesn't have a neighbor through the sideset. 
+
+!syntax parameters /Mesh/FlipSidesetGenerator
+
+!syntax inputs /Mesh/FlipSidesetGenerator
+
+!syntax children /Mesh/FlipSidesetGenerator
@@ -0,0 +1,24 @@
+#pragma once
+
+#include "MeshGenerator.h"
+
+/**
+ * MeshGenerator for flipping sideset
+ */
+class FlipSidesetGenerator : public MeshGenerator
+{
+public:
+  static InputParameters validParams();
+
+  FlipSidesetGenerator(const InputParameters & parameters);
+
+protected:
+  std::unique_ptr<MeshBase> generate() override;
+
+private:
+  ///Input mesh the operation will be applied to
+  std::unique_ptr<MeshBase> & _input;
+
+  ///Name of the sideset to flip
+  const BoundaryName _sideset_name;
+};
@@ -0,0 +1,87 @@
+//* This file is part of the MOOSE framework
+//* https://www.mooseframework.org
+//*
+//* All rights reserved, see COPYRIGHT for full restrictions
+//* https://github.com/idaholab/moose/blob/master/COPYRIGHT
+//*
+//* Licensed under LGPL 2.1, please see LICENSE for details
+//* https://www.gnu.org/licenses/lgpl-2.1.html
+
+#include "FlipSidesetGenerator.h"
+
+#include "CastUniquePointer.h"
+
+registerMooseObject("MooseApp", FlipSidesetGenerator);
+
+InputParameters
+FlipSidesetGenerator::validParams()
+{
+  InputParameters params = MeshGenerator::validParams();
+  params.addClassDescription("A Mesh Generator which flips a given sideset");
+  params.addRequiredParam<MeshGeneratorName>("input", "The mesh we want to modify");
+  params.addRequiredParam<BoundaryName>("boundary", "The sideset (boundary) that will be flipped");
+  return params;
+}
+
+FlipSidesetGenerator::FlipSidesetGenerator(const InputParameters & parameters)
+  : MeshGenerator(parameters),
+    _input(getMesh("input")),
+    _sideset_name(getParam<BoundaryName>("boundary"))
+{
+}
+
+std::unique_ptr<MeshBase>
+FlipSidesetGenerator::generate()
+{
+  //get boundary info
+  BoundaryInfo & boundary_info = _input->get_boundary_info();
+  //get id of the input sideset
+  boundary_id_type sideset_id = boundary_info.get_id_by_name(_sideset_name);
+
+  //Throw an error if the sideset doesn't exist
+  if (sideset_id == libMesh::BoundaryInfo::invalid_id)
+    mooseError("sideset doesn't exist in mesh");
+
+  //get sideset map
+  std::multimap<const Elem *, std::pair<unsigned short int, boundary_id_type>> sideset_map = boundary_info.get_sideset_map();
+
+  //old_elem is the original element attached to the sideset before flipping
+  //new_elem is the element attached to the sideset after flipping
+  for(const auto & [old_elem, id_pair] : sideset_map)
+  {
+    boundary_id_type boundary_id = std::get<1>(id_pair);
+    if (boundary_id == sideset_id)
+    {
+      unsigned short int old_side_id = std::get<0>(id_pair);
+      dof_id_type old_elem_id = old_elem->id();
+      const Elem * new_elem = old_elem->neighbor_ptr(old_side_id);
+
+      //Throw an error if the old element doesn't have a neighbor on the old side
+      if (!new_elem)
+        mooseError("elem " + std::to_string(old_elem_id) + " doesn't have a neighbor through side " + 
+                    std::to_string(old_side_id) + " therefore it can't be flipped");
+
+      unsigned int new_elem_n_sides = new_elem->n_sides();
+      unsigned int new_side_id;
+
+      //To find the new_side_id:
+      //loop over new_elem sides until you find the neighbor which have the same id as the old elem
+      for (unsigned int i = 0; i < new_elem_n_sides; ++i)
+      {
+        const Elem * neighbor = new_elem->neighbor_ptr(i);
+        if(neighbor)
+        {
+          dof_id_type neighbor_id = neighbor->id();
+          if(neighbor_id == old_elem_id)
+          {
+            new_side_id = i;
+            boundary_info.remove_side(old_elem, old_side_id, sideset_id);
+            boundary_info.add_side(new_elem, new_side_id, sideset_id);
+            break;
+          } 
+        }
+      }
+    }    
+  } 
+  return dynamic_pointer_cast<MeshBase>(_input);
+}
@@ -0,0 +1,97 @@
+[Mesh]
+    [gmg]
+        type = GeneratedMeshGenerator
+        dim = 2
+        nx = 3
+        ny = 3
+        xmax = 3
+        ymax = 3
+    []
+    [s1]
+        type = ParsedGenerateSideset
+        input = gmg
+        combinatorial_geometry = 'x > 0.9 & x < 1.1 & y > -0.1 & y < 1.1'
+        normal = '1 0 0'
+        new_sideset_name = s1
+    []
+    [s2]
+        type = ParsedGenerateSideset
+        input = s1
+        combinatorial_geometry = 'x > 0.9 & x < 2.1 & y > 0.9 & y < 1.1'
+        normal = '0 1 0'
+        new_sideset_name = s2
+    []
+    [s3]
+        type = ParsedGenerateSideset
+        input = s2
+        combinatorial_geometry = 'x > 1.9 & x < 2.1 & y > 0.9 & y < 2.1'
+        normal = '1 0 0'
+        new_sideset_name = s3
+    []
+    [s4]
+        type = ParsedGenerateSideset
+        input = s3
+        combinatorial_geometry = 'x > 1.9 & x < 3.1 & y > 1.9 & y < 2.1'
+        normal = '0 1 0'
+        new_sideset_name = s4
+    []
+    [sideset]
+        type = SideSetsFromBoundingBoxGenerator
+        input = s4
+        bottom_left = '0 0 0'
+        top_right = '3 3 3'
+        boundaries_old = 's1 s2 s3 s4'
+        boundary_new = 's_combined'
+    []
+    [flip]
+        type = FlipSidesetGenerator
+        input = sideset
+        boundary = s_combined
+    []
+[]
+
+[AuxVariables]
+    [u]
+    []
+[]
+
+[AuxKernels]
+    [diffusion]
+        type = FunctionAux
+        variable = u
+        function = func
+    []
+[]
+
+[Functions]
+    [func]
+        type = ParsedFunction
+        expression = x+y
+    []
+[]
+
+[Problem]
+    type = FEProblem
+    solve = false
+[]
+
+[Postprocessors]
+    [flux]
+        type = SideDiffusiveFluxIntegral
+        variable = u
+        boundary = s_combined
+        diffusivity = 1
+    []
+    [area]
+        type = AreaPostprocessor
+        boundary = s_combined
+    []
+[]
+
+[Executioner]
+    type = Steady
+[]
+
+[Outputs]
+    csv = true
+[]
@@ -0,0 +1,76 @@
+[Mesh]
+  [gmg]
+    type = GeneratedMeshGenerator
+    dim = 3
+    nx = 3
+    ny = 3
+    nz = 3
+    xmax = 3
+    ymax = 3
+    zmax = 3
+  []
+  [subdomains]
+    type = ParsedSubdomainMeshGenerator
+    input = gmg
+    combinatorial_geometry = 'x < 1 & y > 1 & y < 2'
+    block_id = 1
+  []
+  [sideset]
+    type = ParsedGenerateSideset
+    input = subdomains
+    combinatorial_geometry = 'z < 1'
+    included_subdomains = '1'
+    normal = '1 0 0'
+    new_sideset_name = interior
+  []
+  [flip]
+    type = FlipSidesetGenerator
+    input = sideset
+    boundary = interior
+  []
+[]
+[AuxVariables]
+    [u]
+    []
+[]
+
+[AuxKernels]
+    [diffusion]
+        type = FunctionAux
+        variable = u
+        function = func
+    []
+[]
+
+[Functions]
+    [func]
+        type = ParsedFunction
+        expression = x+y+z
+    []
+[]
+
+[Problem]
+    type = FEProblem
+    solve = false
+[]
+
+[Postprocessors]
+    [flux]
+        type = SideDiffusiveFluxIntegral
+        variable = u
+        boundary = interior
+        diffusivity = 1
+    []
+    [area]
+        type = AreaPostprocessor
+        boundary = interior
+    []
+[]
+
+[Executioner]
+    type = Steady
+[]
+
+[Outputs]
+    csv = true
+[]
@@ -0,0 +1,3 @@
+time,area,flux
+0,0,0
+1,4,4
@@ -0,0 +1,3 @@
+time,area,flux
+0,0,0
+1,1,1
@@ -0,0 +1,16 @@
+[Mesh]
+    [gmg]
+        type = GeneratedMeshGenerator
+        dim = 2
+        nx = 1
+        ny = 1
+    []
+    [flip]
+        type = FlipSidesetGenerator
+        input = gmg
+        boundary = 'right'
+    []
+[]
+[Outputs]
+    exodus = true
+[]
@@ -0,0 +1,16 @@
+[Mesh]
+    [gmg]
+        type = GeneratedMeshGenerator
+        dim = 2
+        nx = 1
+        ny = 1
+    []
+    [flip]
+        type = FlipSidesetGenerator
+        input = gmg
+        boundary = 'side'
+    []
+[]
+[Outputs]
+    exodus = true
+[]
@@ -0,0 +1,40 @@
+[Tests]
+    [flux_2D]
+      type = 'CSVDiff'
+      input = 'flux_flip_2D.i'
+      csvdiff = 'flux_flip_2D_out.csv'
+      recover = false
+      issues = '#25528'
+      design = 'FlipSidesetGenerator.md'
+      requirement = 'This system allows the sideset to be flipped'
+    []
+
+    [flux_3D]
+      type = 'CSVDiff'
+      input = 'flux_flip_3D.i'
+      csvdiff = 'flux_flip_3D_out.csv'
+      recover = false
+      requirement = 'This system allows the sideset to be flipped'
+      design = 'FlipSidesetGenerator.md'
+      issues = '#25528'
+    []
+    [no_sideset_exception]
+      type = 'RunException'
+      input = 'no_sideset.i'
+      cli_args = '--mesh-only'
+      expect_err = "sideset doesn't exist in mesh"
+      requirement = 'The system shall error'
+      design = 'FlipSidesetGenerator.md'
+      issues = '#25528'
+    []
+    [no_neighbor_exception]
+      type = 'RunException'
+      input = 'no_neighbor.i'
+      cli_args = '--mesh-only'
+      expect_err = "neighbor"
+      requirement = 'The system shall error'
+      design = 'FlipSidesetGenerator.md'
+      issues = '#25528'
+    []
+[]
+