Add test

refs idaholab#26592

framework/doc/content/syntax/AuxKernels/index.md

@@ -67,12 +67,12 @@ is done to allow the syntax to be consistent regardless of the AuxKernel flavor:
 
 In order to compute properties in the mortar sense, it is necessary to loop over the mortar segment
 mesh to spatially integrate variables. `MortarNodalAuxKernel`s offer this functionality where these "weighted" variables,
-which intervene in the computation of contact constraints and their residuals, can be coupled to generate the desired output value. 
-Therefore, if postprocessing of mortar quantities is required, nodal mortar auxiliary kernels can be employed. 
+which intervene in the computation of contact constraints and their residuals, can be coupled to generate the desired output value.
+Therefore, if postprocessing of mortar quantities is required, nodal mortar auxiliary kernels can be employed.
 Objects inheriting from `MortarNodalAuxKernel` allow for said operations on the mortar lower-dimensional domains featuring similar
 functionality to other nodal auxiliary kernels, including the possibility of computing quantities in an
 `incremental` manner.
- 
+
 ## Execute Flags
 
 AuxKernel objects inherit from the [SetupInterface.md] so they include the "execute_on" variable.
@@ -88,6 +88,17 @@ execution of a simulation. In this case, the `EXEC_LINEAR` flag should be remove
 `EXEC_INITIAL` flag should be added to perform the auxiliary variable calculation during the initial
 setup phase as well.
 
+## Populating lower-dimensional auxiliary variables
+
+Lower-dimensional auxiliary variables may be populated using boundary restricted
+auxiliary kernels. The boundary restriction of the aux kernel should be
+coincident with (a subset of) the lower-dimensional blocks that the
+lower-dimensional variable lives on. Using a boundary restricted auxiliary
+kernel as opposed to a lower-d block-restricted auxiliary kernel (which is not
+supported) allows pulling
+in coincident face evaluations of higher-dimensional variables and material
+properties as well as evaluations of coupled lower-dimensional variables.
+
 ## Example A: Post processing with AuxKernel
 
 The following example is extracted from step 4 of the

framework/src/auxkernels/AuxKernel.C

@@ -351,14 +351,16 @@ AuxKernelTempl<ComputeValueType>::compute()
       _local_ke.resize(_n_local_dofs, _n_local_dofs);
       _local_ke.zero();
 
+      const auto & test = _lower_d_calc ? _var.phiLower() : _test;
+
       // assemble the local mass matrix and the load
-      for (unsigned int i = 0; i < _test.size(); i++)
+      for (unsigned int i = 0; i < test.size(); i++)
         for (_qp = 0; _qp < _qrule->n_points(); _qp++)
         {
-          ComputeValueType t = _JxW[_qp] * _coord[_qp] * _test[i][_qp];
+          ComputeValueType t = _JxW[_qp] * _coord[_qp] * test[i][_qp];
           _local_re(i) += t * computeValue();
-          for (unsigned int j = 0; j < _test.size(); j++)
-            _local_ke(i, j) += t * _test[j][_qp];
+          for (unsigned int j = 0; j < test.size(); j++)
+            _local_ke(i, j) += t * test[j][_qp];
         }
       // mass matrix is always SPD but in case of boundary restricted, it will be rank deficient
       _local_sol.resize(_n_local_dofs);

test/tests/auxkernels/lower_d_var/gold/lower-d-aux-var_out.csv

@@ -0,0 +1,3 @@
+time,avg_lower_constant_bottom,avg_lower_constant_left,avg_lower_constant_right,avg_lower_constant_top,avg_lower_first_bottom,avg_lower_first_left,avg_lower_first_right,avg_lower_first_top
+0,0,0,0,0,0,0,0,0
+1,0.5,0.5,1.5,1.5,0.5,0.5,1.5,1.5

test/tests/auxkernels/lower_d_var/lower-d-aux-var.i

@@ -0,0 +1,141 @@
+[Mesh]
+  [gen]
+    type = GeneratedMeshGenerator
+    dim = 2
+    nx = 10
+    ny = 10
+  []
+  [lower_left]
+    type = LowerDBlockFromSidesetGenerator
+    input = gen
+    sidesets = 'left'
+    new_block_name = 'lower_left'
+  []
+  [lower_right]
+    type = LowerDBlockFromSidesetGenerator
+    input = lower_left
+    sidesets = 'right'
+    new_block_name = 'lower_right'
+  []
+  [lower_top]
+    type = LowerDBlockFromSidesetGenerator
+    input = lower_right
+    sidesets = 'top'
+    new_block_name = 'lower_top'
+  []
+  [lower_bottom]
+    type = LowerDBlockFromSidesetGenerator
+    input = lower_top
+    sidesets = 'bottom'
+    new_block_name = 'lower_bottom'
+  []
+[]
+
+[Problem]
+  solve = false
+[]
+
+[AuxVariables]
+  [lower_constant]
+    family = MONOMIAL
+    order = CONSTANT
+    block = 'lower_top lower_right lower_bottom lower_left'
+  []
+  [lower_first]
+    family = MONOMIAL
+    order = FIRST
+    block = 'lower_top lower_right lower_bottom lower_left'
+  []
+  [higher]
+    family = MONOMIAL
+    order = CONSTANT
+    block = '0'
+  []
+[]
+
+[AuxKernels]
+  [lower_constant]
+    type = MaterialRealAux
+    property = 'prop'
+    variable = lower_constant
+    boundary = 'top bottom right left'
+  []
+  [lower_first]
+    type = MaterialRealAux
+    property = 'prop'
+    variable = lower_first
+    boundary = 'top bottom right left'
+  []
+  [higher]
+    type = MaterialRealAux
+    property = 'prop'
+    variable = higher
+    block = 0
+  []
+[]
+
+[Functions]
+  [func]
+    type = ParsedFunction
+    expression = 'x + y'
+  []
+[]
+
+[Materials]
+  [func]
+    type = GenericFunctionMaterial
+    prop_names = 'prop'
+    prop_values = 'func'
+  []
+[]
+
+[Outputs]
+  csv = true
+[]
+
+[Executioner]
+  type = Steady
+[]
+
+[Postprocessors]
+  [avg_lower_constant_left]
+    type = ElementAverageValue
+    variable = lower_constant
+    block = lower_left
+  []
+  [avg_lower_first_left]
+    type = ElementAverageValue
+    variable = lower_first
+    block = lower_left
+  []
+  [avg_lower_constant_bottom]
+    type = ElementAverageValue
+    variable = lower_constant
+    block = lower_bottom
+  []
+  [avg_lower_first_bottom]
+    type = ElementAverageValue
+    variable = lower_first
+    block = lower_bottom
+  []
+  [avg_lower_constant_top]
+    type = ElementAverageValue
+    variable = lower_constant
+    block = lower_top
+  []
+  [avg_lower_first_top]
+    type = ElementAverageValue
+    variable = lower_first
+    block = lower_top
+  []
+  [avg_lower_constant_right]
+    type = ElementAverageValue
+    variable = lower_constant
+    block = lower_right
+  []
+  [avg_lower_first_right]
+    type = ElementAverageValue
+    variable = lower_first
+    block = lower_right
+  []
+[]

test/tests/auxkernels/lower_d_var/tests

@@ -0,0 +1,10 @@
+[Tests]
+  design = 'AuxKernels/index.md'
+  issues = '#26592'
+  [csv]
+    type = CSVDiff
+    input = lower-d-aux-var.i
+    csvdiff = lower-d-aux-var_out.csv
+    requirement = 'The system shall allow populating lower-dimensional auxiliary variables using boundary restricted auxiliary kernels.'
+  []
+[]