From bd9d205f831a0eddfa265f91c57813f32edb13f6 Mon Sep 17 00:00:00 2001
From: SudiptaBiswas <sudipta.besu@gmail.com>
Date: Wed, 17 Jul 2024 11:17:40 -0700
Subject: [PATCH] Add option to use absolute value in
 ElementIntegralVariablePostprocessor  #28162`

---
 .../ElementIntegralVariablePostprocessor.h    |  2 +
 .../ElementIntegralVariablePostprocessor.C    | 10 ++-
 .../element_integral_absolute_test.i          | 64 +++++++++++++++++++
 .../postprocessors/element_integral/tests     | 12 +++-
 4 files changed, 84 insertions(+), 4 deletions(-)
 create mode 100644 test/tests/postprocessors/element_integral/element_integral_absolute_test.i

diff --git a/framework/include/postprocessors/ElementIntegralVariablePostprocessor.h b/framework/include/postprocessors/ElementIntegralVariablePostprocessor.h
index 62aa13d01f4d..e3012a9f4a19 100644
--- a/framework/include/postprocessors/ElementIntegralVariablePostprocessor.h
+++ b/framework/include/postprocessors/ElementIntegralVariablePostprocessor.h
@@ -33,4 +33,6 @@ class ElementIntegralVariablePostprocessor : public ElementIntegralPostprocessor
   const VariableValue & _u;
   /// Holds the solution gradient at the current quadrature points
   const VariableGradient & _grad_u;
+  /// Option to use absolute variable value
+  bool _use_abs_value;
 };
diff --git a/framework/src/postprocessors/ElementIntegralVariablePostprocessor.C b/framework/src/postprocessors/ElementIntegralVariablePostprocessor.C
index 3075d92e96d2..2dcad08538e3 100644
--- a/framework/src/postprocessors/ElementIntegralVariablePostprocessor.C
+++ b/framework/src/postprocessors/ElementIntegralVariablePostprocessor.C
@@ -17,6 +17,8 @@ ElementIntegralVariablePostprocessor::validParams()
   InputParameters params = ElementIntegralPostprocessor::validParams();
   params.addRequiredCoupledVar("variable", "The name of the variable that this object operates on");
   params.addClassDescription("Computes a volume integral of the specified variable");
+  params.addParam<bool>(
+      "use_absolute_value", false, "Whether to use abolsute value of the variable or not");
   return params;
 }
 
@@ -29,7 +31,8 @@ ElementIntegralVariablePostprocessor::ElementIntegralVariablePostprocessor(
                                  Moose::VarKindType::VAR_ANY,
                                  Moose::VarFieldType::VAR_FIELD_STANDARD),
     _u(coupledValue("variable")),
-    _grad_u(coupledGradient("variable"))
+    _grad_u(coupledGradient("variable")),
+    _use_abs_value(getParam<bool>("use_absolute_value"))
 {
   addMooseVariableDependency(&mooseVariableField());
 }
@@ -37,5 +40,8 @@ ElementIntegralVariablePostprocessor::ElementIntegralVariablePostprocessor(
 Real
 ElementIntegralVariablePostprocessor::computeQpIntegral()
 {
-  return _u[_qp];
+  if (_use_abs_value)
+    return std::abs(_u[_qp]);
+  else
+    return _u[_qp];
 }
diff --git a/test/tests/postprocessors/element_integral/element_integral_absolute_test.i b/test/tests/postprocessors/element_integral/element_integral_absolute_test.i
new file mode 100644
index 000000000000..13c9f01166d8
--- /dev/null
+++ b/test/tests/postprocessors/element_integral/element_integral_absolute_test.i
@@ -0,0 +1,64 @@
+[Mesh]
+  [./square]
+    type = GeneratedMeshGenerator
+    nx = 2
+    ny = 2
+    dim = 2
+  [../]
+[]
+
+[Variables]
+  active = 'u'
+
+  [./u]
+    order = FIRST
+    family = LAGRANGE
+  [../]
+[]
+
+[Kernels]
+  active = 'diff'
+
+  [./diff]
+    type = Diffusion
+    variable = u
+  [../]
+[]
+
+[BCs]
+  active = 'left right'
+
+  [./left]
+    type = DirichletBC
+    variable = u
+    boundary = 3
+    value = 0
+  [../]
+
+  [./right]
+    type = DirichletBC
+    variable = u
+    boundary = 1
+    value = -1
+  [../]
+[]
+
+[Executioner]
+  type = Steady
+
+  solve_type = 'PJFNK'
+[]
+
+[Postprocessors]
+  [./integral]
+    type = ElementIntegralVariablePostprocessor
+    variable = u
+    use_absolute_value = true
+  [../]
+[]
+
+[Outputs]
+  file_base = out
+  exodus = false
+  csv = true
+[]
diff --git a/test/tests/postprocessors/element_integral/tests b/test/tests/postprocessors/element_integral/tests
index 1751be3b67ea..fba50656ed0d 100644
--- a/test/tests/postprocessors/element_integral/tests
+++ b/test/tests/postprocessors/element_integral/tests
@@ -10,7 +10,7 @@
       input = 'element_integral_test.i'
       csvdiff = 'out.csv'
 
-      detail = 'over the whole domain and'
+      detail = 'over the whole domain, and'
     []
 
     [block_test]
@@ -18,7 +18,15 @@
       input = 'element_block_integral_test.i'
       csvdiff = 'out_block.csv'
 
-      detail = 'over a subset of the domain.'
+      detail = 'over a subset of the domain,'
+    []
+
+    [test_abs]
+      type = 'CSVDiff'
+      input = 'element_integral_absolute_test.i'
+      csvdiff = 'out.csv'
+
+      detail = 'and also optionally, using the absolute variable value.'
     []
   []
 []