ModularGapConductanceConstraint

Computes the residual and Jacobian contributions for the 'Lagrange Multiplier' implementation of the thermal contact problem. For more information, see the detailed description here: http://tinyurl.com/gmmhbe9

The ModularGapConductanceConstraint class is used specify a heat flux across a gap. The flux is computed by user objects derived from GapFluxModelBase. Such as

Multiple models can be specified with their contributions getting summed up.

Gap geometry types

Plate, cylindrical, and spherical gap geometries can be specified using the "gap_geometry_type" parameter.

For cylindrical geometries, e.g. gap_geometry_type = cylinder, the axis of the cylinder can be specified using the "cylinder_axis_point_1" and "cylinder_axis_point_2" parameters. In 2D Cartesian coordinate systems (e.g. Mesh/coord_type=XYZ), these parameters can be omitted to automatically determine the cylinder axis. This is accomplished by averaging positions over the primary side set, which should yield the center of the cylinder, assuming the side set spans the entire 360 degree rotation around the theoretical axis. The axis is then extended in z-direction.

For spherical geometries the origin of the sphere can be specified using the "sphere_origin" parameter. If the parameter is omitted, the sphere origin is deduced by averaging positions over the primary side set.

note

If the gap is sliced by a symmetry plane (e.g. only a quarter of a cylinder or an eighth of a sphere are modeled), the positional average over the primary side set will not yield the correct origin or axis and they will need to be supplied manually.

Input Parameters

primary_boundaryThe name of the primary boundary sideset.
C++ Type:BoundaryName
Controllable:No
Description:The name of the primary boundary sideset.
primary_subdomainThe name of the primary subdomain.
C++ Type:SubdomainName
Controllable:No
Description:The name of the primary subdomain.
secondary_boundaryThe name of the secondary boundary sideset.
C++ Type:BoundaryName
Controllable:No
Description:The name of the secondary boundary sideset.
secondary_subdomainThe name of the secondary subdomain.
C++ Type:SubdomainName
Controllable:No
Description:The name of the secondary subdomain.

Required Parameters

aux_lmAuxiliary Lagrange multiplier variable that is utilized together with the Petrov-Galerkin approach.
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:Auxiliary Lagrange multiplier variable that is utilized together with the Petrov-Galerkin approach.
compute_lm_residualsTrueWhether to compute Lagrange Multiplier residuals
Default:True
C++ Type:bool
Controllable:No
Description:Whether to compute Lagrange Multiplier residuals
compute_primal_residualsTrueWhether to compute residuals for the primal variable.
Default:True
C++ Type:bool
Controllable:No
Description:Whether to compute residuals for the primal variable.
correct_edge_droppingFalseWhether to enable correct edge dropping treatment for mortar constraints. When disabled any Lagrange Multiplier degree of freedom on a secondary element without full primary contributions will be set (strongly) to 0.
Default:False
C++ Type:bool
Controllable:No
Description:Whether to enable correct edge dropping treatment for mortar constraints. When disabled any Lagrange Multiplier degree of freedom on a secondary element without full primary contributions will be set (strongly) to 0.
debug_meshFalseWhether this constraint is going to enable mortar segment mesh debug information. An exodusfile will be generated if the user sets this flag to true
Default:False
C++ Type:bool
Controllable:No
Description:Whether this constraint is going to enable mortar segment mesh debug information. An exodusfile will be generated if the user sets this flag to true
displacementsDisplacement variables
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:Displacement variables
ghost_higher_d_neighborsFalseWhether we should ghost higher-dimensional neighbors. This is necessary when we are doing second order mortar with finite volume primal variables, because in order for the method to be second order we must use cell gradients, which couples in the neighbor cells.
Default:False
C++ Type:bool
Controllable:No
Description:Whether we should ghost higher-dimensional neighbors. This is necessary when we are doing second order mortar with finite volume primal variables, because in order for the method to be second order we must use cell gradients, which couples in the neighbor cells.
ghost_point_neighborsFalseWhether we should ghost point neighbors of secondary face elements, and consequently also their mortar interface couples.
Default:False
C++ Type:bool
Controllable:No
Description:Whether we should ghost point neighbors of secondary face elements, and consequently also their mortar interface couples.
interpolate_normalsTrueWhether to interpolate the nodal normals (e.g. classic idea of evaluating field at quadrature points). If this is set to false, then non-interpolated nodal normals will be used, and then the _normals member should be indexed with _i instead of _qp
Default:True
C++ Type:bool
Controllable:No
Description:Whether to interpolate the nodal normals (e.g. classic idea of evaluating field at quadrature points). If this is set to false, then non-interpolated nodal normals will be used, and then the _normals member should be indexed with _i instead of _qp
matrix_onlyFalseWhether this object is only doing assembly to matrices (no vectors)
Default:False
C++ Type:bool
Controllable:No
Description:Whether this object is only doing assembly to matrices (no vectors)
minimum_projection_angle40Parameter to control which angle (in degrees) is admissible for the creation of mortar segments. If set to a value close to zero, very oblique projections are allowed, which can result in mortar segments solving physics not meaningfully, and overprojection of primary nodes onto the mortar segment mesh in extreme cases. This parameter is mostly intended for mortar mesh debugging purposes in two dimensions.
Default:40
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Parameter to control which angle (in degrees) is admissible for the creation of mortar segments. If set to a value close to zero, very oblique projections are allowed, which can result in mortar segments solving physics not meaningfully, and overprojection of primary nodes onto the mortar segment mesh in extreme cases. This parameter is mostly intended for mortar mesh debugging purposes in two dimensions.
periodicFalseWhether this constraint is going to be used to enforce a periodic condition. This has the effect of changing the normals vector for projection from outward to inward facing
Default:False
C++ Type:bool
Controllable:No
Description:Whether this constraint is going to be used to enforce a periodic condition. This has the effect of changing the normals vector for projection from outward to inward facing
primary_variablePrimal variable on primary surface. If this parameter is not provided then the primary variable will be initialized to the secondary variable
C++ Type:VariableName
Unit:(no unit assumed)
Controllable:No
Description:Primal variable on primary surface. If this parameter is not provided then the primary variable will be initialized to the secondary variable
quadratureDEFAULTQuadrature rule to use on mortar segments. For 2D mortar DEFAULT is recommended. For 3D mortar, QUAD meshes are integrated using triangle mortar segments. While DEFAULT quadrature order is typically sufficiently accurate, exact integration of QUAD mortar faces requires SECOND order quadrature for FIRST variables and FOURTH order quadrature for SECOND order variables.
Default:DEFAULT
C++ Type:MooseEnum
Options:DEFAULT, FIRST, SECOND, THIRD, FOURTH
Controllable:No
Description:Quadrature rule to use on mortar segments. For 2D mortar DEFAULT is recommended. For 3D mortar, QUAD meshes are integrated using triangle mortar segments. While DEFAULT quadrature order is typically sufficiently accurate, exact integration of QUAD mortar faces requires SECOND order quadrature for FIRST variables and FOURTH order quadrature for SECOND order variables.
secondary_variablePrimal variable on secondary surface.
C++ Type:VariableName
Unit:(no unit assumed)
Controllable:No
Description:Primal variable on secondary surface.
use_petrov_galerkinFalseWhether to use the Petrov-Galerkin approach for the mortar-based constraints. If set to true, we use the standard basis as the test function and dual basis as the shape function for the interpolation of the Lagrange multiplier variable.
Default:False
C++ Type:bool
Controllable:No
Description:Whether to use the Petrov-Galerkin approach for the mortar-based constraints. If set to true, we use the standard basis as the test function and dual basis as the shape function for the interpolation of the Lagrange multiplier variable.
variableThe name of the lagrange multiplier variable that this constraint is applied to. This parameter may not be supplied in the case of using penalty methods for example
C++ Type:NonlinearVariableName
Unit:(no unit assumed)
Controllable:No
Description:The name of the lagrange multiplier variable that this constraint is applied to. This parameter may not be supplied in the case of using penalty methods for example

Optional Parameters

absolute_value_vector_tagsThe tags for the vectors this residual object should fill with the absolute value of the residual contribution
C++ Type:std::vector<TagName>
Controllable:No
Description:The tags for the vectors this residual object should fill with the absolute value of the residual contribution
extra_matrix_tagsThe extra tags for the matrices this Kernel should fill
C++ Type:std::vector<TagName>
Controllable:No
Description:The extra tags for the matrices this Kernel should fill
extra_vector_tagsThe extra tags for the vectors this Kernel should fill
C++ Type:std::vector<TagName>
Controllable:No
Description:The extra tags for the vectors this Kernel should fill
matrix_tagssystemThe tag for the matrices this Kernel should fill
Default:system
C++ Type:MultiMooseEnum
Options:nontime, system
Controllable:No
Description:The tag for the matrices this Kernel should fill
vector_tagsnontimeThe tag for the vectors this Kernel should fill
Default:nontime
C++ Type:MultiMooseEnum
Options:nontime, time
Controllable:No
Description:The tag for the vectors this Kernel should fill

Contribution To Tagged Field Data Parameters

control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Controllable:No
Description:Adds user-defined labels for accessing object parameters via control logic.
enableTrueSet the enabled status of the MooseObject.
Default:True
C++ Type:bool
Controllable:Yes
Description:Set the enabled status of the MooseObject.
implicitTrueDetermines whether this object is calculated using an implicit or explicit form
Default:True
C++ Type:bool
Controllable:No
Description:Determines whether this object is calculated using an implicit or explicit form
search_methodnearest_node_connected_sidesChoice of search algorithm. All options begin by finding the nearest node in the primary boundary to a query point in the secondary boundary. In the default nearest_node_connected_sides algorithm, primary boundary elements are searched iff that nearest node is one of their nodes. This is fast to determine via a pregenerated node-to-elem map and is robust on conforming meshes. In the optional all_proximate_sides algorithm, primary boundary elements are searched iff they touch that nearest node, even if they are not topologically connected to it. This is more CPU-intensive but is necessary for robustness on any boundary surfaces which has disconnections (such as Flex IGA meshes) or non-conformity (such as hanging nodes in adaptively h-refined meshes).
Default:nearest_node_connected_sides
C++ Type:MooseEnum
Options:nearest_node_connected_sides, all_proximate_sides
Controllable:No
Description:Choice of search algorithm. All options begin by finding the nearest node in the primary boundary to a query point in the secondary boundary. In the default nearest_node_connected_sides algorithm, primary boundary elements are searched iff that nearest node is one of their nodes. This is fast to determine via a pregenerated node-to-elem map and is robust on conforming meshes. In the optional all_proximate_sides algorithm, primary boundary elements are searched iff they touch that nearest node, even if they are not topologically connected to it. This is more CPU-intensive but is necessary for robustness on any boundary surfaces which has disconnections (such as Flex IGA meshes) or non-conformity (such as hanging nodes in adaptively h-refined meshes).
seed0The seed for the master random number generator
Default:0
C++ Type:unsigned int
Controllable:No
Description:The seed for the master random number generator
use_displaced_meshFalseWhether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.
Default:False
C++ Type:bool
Controllable:No
Description:Whether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

Advanced Parameters

cylinder_axis_point_1Start point for line defining cylindrical axis
C++ Type:libMesh::VectorValue<double>
Unit:(no unit assumed)
Controllable:No
Description:Start point for line defining cylindrical axis
cylinder_axis_point_2End point for line defining cylindrical axis
C++ Type:libMesh::VectorValue<double>
Unit:(no unit assumed)
Controllable:No
Description:End point for line defining cylindrical axis
gap_geometry_typeAUTOGap calculation type. The geometry type is used to compute gap distances and scale fluxes to ensure energy balance. If AUTO is selected, the gap geometry is automatically set via the mesh coordinate system.
Default:AUTO
C++ Type:MooseEnum
Options:AUTO, PLATE, CYLINDER, SPHERE
Controllable:No
Description:Gap calculation type. The geometry type is used to compute gap distances and scale fluxes to ensure energy balance. If AUTO is selected, the gap geometry is automatically set via the mesh coordinate system.
max_gap1e+06A maximum gap size
Default:1e+06
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:A maximum gap size
sphere_originOrigin for sphere geometry
C++ Type:libMesh::VectorValue<double>
Unit:(no unit assumed)
Controllable:No
Description:Origin for sphere geometry

Gap Geometry Parameters

gap_flux_modelsList of GapFluxModel user objects
C++ Type:std::vector<UserObjectName>
Controllable:No
Description:List of GapFluxModel user objects

Gap Flux Models Parameters

prop_getter_suffixAn optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.
C++ Type:MaterialPropertyName
Unit:(no unit assumed)
Controllable:No
Description:An optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.
use_interpolated_stateFalseFor the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.
Default:False
C++ Type:bool
Controllable:No
Description:For the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

Material Property Retrieval Parameters

Input Files

(modules/combined/test/tests/gap_heat_transfer_mortar/small-2d/multi_component_mortar_thermal_conduction.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar.i)
(modules/heat_transfer/test/tests/interface_heating_mortar/constraint_joule_heating_dual_material_insulated.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/large_gap_heat_transfer_test_cylinder_mortar_error.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced_radiation_conduction.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced_radiation_conduction_separate.i)
(modules/combined/test/tests/gap_heat_transfer_mortar/small-2d/closed_gap_pressure_dependent_thermal_contact.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar_action/modular_gap_heat_transfer_mortar_displaced_radiation_conduction_verbose.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/large_gap_heat_transfer_test_rz_cylinder_mortar.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced_conduction_function.i)
(modules/heat_transfer/test/tests/interface_heating_mortar/constraint_joule_heating_dual_material.i)
(modules/heat_transfer/test/tests/interface_heating_mortar/transient_joule_heating_constraint.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced_conduction.i)
(modules/heat_transfer/test/tests/interface_heating_mortar/constraint_joule_heating_offset_single_material_insulated.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/closed_gap_prescribed_pressure.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/gap_heat_transfer_3D_mortar.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/large_gap_heat_transfer_test_sphere_mortar.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced_radiation.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/gap_heat_transfer_sphere3D_mortar.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/large_gap_heat_transfer_test_sphere_mortar_error.i)
(modules/combined/test/tests/3d-mortar-projection-tolerancing/test.i)
(modules/combined/test/tests/gap_heat_transfer_mortar/finite-2d/closed_gap_thermomechanical_mortar_contact.i)
(modules/combined/test/tests/gap_heat_transfer_mortar/finite-2d/varied_pressure_thermomechanical_mortar.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/fv_modular_gap_heat_transfer_mortar_radiation_conduction.i)
(modules/heat_transfer/test/tests/interface_heating_mortar/constraint_joule_heating_single_material.i)
(modules/combined/test/tests/gap_heat_transfer_mortar/small-2d/open_gap_pressure_dependent.i)
(modules/heat_transfer/test/tests/interface_heating_mortar/constraint_joule_heating_single_material_insulated.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/gap_heat_transfer_radiation_test.i)
(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/large_gap_heat_transfer_test_cylinder_mortar.i)

References

No citations exist within this document.

(modules/combined/test/tests/gap_heat_transfer_mortar/small-2d/multi_component_mortar_thermal_conduction.i)

## Units in the input file: m-Pa-s-K

[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 40
    ny = 10
    xmax = 1
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 40
    ny = 10
    xmin = 1.
    xmax = 2.
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
  patch_update_strategy = iteration
[]

[Variables]
  [disp_x]
    block = 'left_block right_block'
  []
  [disp_y]
    block = 'left_block right_block'
  []
  [temperature]
    initial_condition = 525.0
  []
  [temperature_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[Physics]
  [SolidMechanics/QuasiStatic]
    [steel]
      strain = SMALL
      add_variables = false
      use_automatic_differentiation = true
      additional_generate_output = 'vonmises_stress'
      additional_material_output_family = 'MONOMIAL'
      additional_material_output_order = 'FIRST'
      block = 'left_block'
    []
    [aluminum]
      strain = SMALL
      add_variables = false
      use_automatic_differentiation = true
      additional_generate_output = 'vonmises_stress'
      additional_material_output_family = 'MONOMIAL'
      additional_material_output_order = 'FIRST'
      block = 'right_block'
    []
  []
[]

[Kernels]
  [HeatDiff_steel]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = steel_thermal_conductivity
    block = 'left_block'
  []
  [HeatTdot_steel]
    type = ADHeatConductionTimeDerivative
    variable = temperature
    specific_heat = steel_heat_capacity
    density_name = steel_density
    block = 'left_block'
  []
  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    block = 'right_block'
  []
  [HeatTdot_aluminum]
    type = ADHeatConductionTimeDerivative
    variable = temperature
    specific_heat = aluminum_heat_capacity
    density_name = aluminum_density
    block = 'right_block'
  []
[]

[BCs]
  [fixed_bottom_edge]
    type = ADDirichletBC
    variable = disp_y
    value = 0
    boundary = 'moving_block_bottom fixed_block_bottom'
  []
  [fixed_outer_edge]
    type = ADDirichletBC
    variable = disp_x
    value = 0
    boundary = 'fixed_block_right'
  []
  [displacement_left_block]
    type = ADFunctionDirichletBC
    variable = disp_x
    function = 'if(t<61, 2.0e-7, -2.0e-8*(t-60))'
    boundary = 'moving_block_left'
  []
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 800
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 250
    boundary = 'fixed_block_right'
  []
[]

[Contact]
  [interface]
    primary = moving_block_right
    secondary = fixed_block_left
    model = frictionless
    formulation = mortar
    correct_edge_dropping = true
  []
[]

[Constraints]
  [thermal_contact]
    type = ModularGapConductanceConstraint
    variable = temperature_interface_lm
    secondary_variable = temperature
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'radiation closed'
    use_displaced_mesh = true
  []
[]

[Materials]
  [steel_elasticity_tensor]
    type = ADComputeIsotropicElasticityTensor
    youngs_modulus = 1.93e11 #in Pa, 193 GPa, stainless steel 304
    poissons_ratio = 0.29
    block = 'left_block'
  []
  [steel_stress]
    type = ADComputeLinearElasticStress
    block = 'left_block'
  []
  [steel_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'steel_density steel_thermal_conductivity steel_heat_capacity'
    prop_values = '  8e3          16.2                       0.5' ## for stainless steel 304
    block = 'left_block'
  []

  [aluminum_elasticity_tensor]
    type = ADComputeIsotropicElasticityTensor
    youngs_modulus = 6.8e10 #in Pa, 68 GPa, aluminum
    poissons_ratio = 0.36
    block = 'right_block'
  []
  [aluminum_stress]
    type = ADComputeLinearElasticStress
    block = 'right_block'
  []
  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density aluminum_thermal_conductivity aluminum_heat_capacity'
    prop_values = ' 2.7e3            210                          0.9'
    block = 'right_block'
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    secondary_emissivity = 0.25
    primary_emissivity = 0.6
    temperature = temperature
    boundary = moving_block_right
  []
  [closed]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = steel_thermal_conductivity
    secondary_conductivity = aluminum_thermal_conductivity
    temperature = temperature
    contact_pressure = interface_normal_lm
    primary_hardness = 1.0
    secondary_hardness = 1.0
    boundary = moving_block_right
  []
[]

[Postprocessors]
  [steel_pt_interface_temperature]
    type = NodalVariableValue
    nodeid = 245
    variable = temperature
  []
  [aluminum_pt_interface_temperature]
    type = NodalVariableValue
    nodeid = 657
    variable = temperature
  []
  [aluminum_element_interface_stress]
    type = ElementalVariableValue
    variable = vonmises_stress
    elementid = 560
  []
  [interface_heat_flux_steel]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = moving_block_right
    diffusivity = steel_thermal_conductivity
  []
  [interface_heat_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = fixed_block_left
    diffusivity = aluminum_thermal_conductivity
  []
[]


[Executioner]
  type = Transient
  solve_type = NEWTON
  automatic_scaling = false
  line_search = 'none'

  # mortar contact solver options
  petsc_options = '-snes_converged_reason -pc_svd_monitor'
  petsc_options_iname = '-pc_type -pc_factor_mat_solver_type'
  petsc_options_value = ' lu       superlu_dist'
  snesmf_reuse_base = false

  nl_rel_tol = 1e-10
  nl_max_its = 20
  l_max_its = 50

  dt = 60
  end_time = 120
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar.i)

[Mesh]
  [file]
    type = FileMeshGenerator
    file = 2blk-gap.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '101'
    new_block_id = '10001'
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '100'
    new_block_id = '10000'
    new_block_name = 'primary_lower'
    input = secondary
  []
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Variables]
  [temp]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []

  [lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[Materials]
  [left]
    type = HeatConductionMaterial
    block = 1
    thermal_conductivity = 1000
    specific_heat = 1
  []

  [right]
    type = HeatConductionMaterial
    block = 2
    thermal_conductivity = 500
    specific_heat = 1
  []
[]

[Kernels]
  [hc]
    type = HeatConduction
    variable = temp
    use_displaced_mesh = false
    block = '1 2'
  []
[]

[UserObjects]
  [simple]
    type = GapFluxModelSimple
    k = 100
    temperature = temp
    boundary = 100
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    primary_boundary = 100
    primary_subdomain = 10000
    secondary_boundary = 101
    secondary_subdomain = 10001
    gap_flux_models = simple
  []
[]

[BCs]
  [left]
    type = DirichletBC
    variable = temp
    boundary = 'left'
    value = 1
  []

  [right]
    type = DirichletBC
    variable = temp
    boundary = 'right'
    value = 0
  []
[]

[Preconditioning]
  [fmp]
    type = SMP
    full = true
  []
[]

[Executioner]
  type = Steady
  solve_type = 'PJFNK'
  nl_rel_tol = 1e-11
[]

[Outputs]
  exodus = true
[]

(modules/heat_transfer/test/tests/interface_heating_mortar/constraint_joule_heating_dual_material_insulated.i)

## Units in the input file: m-Pa-s-K-V

# Using the steady-state Fourier's law, the temperature at the interface in each block,
# in the case where thermal contact between the two blocks at the interface is not
# considered, (steel block on left, aluminum on right) is calculated as:
#
#   T_{interface - steel} = 816.849K
#   T_{interface - aluminum} = 339.871K
# which matches the simulation results to the 6 decimal places shown.
# As expected, the heat flux resulting from the volumetric Joule heating source is
# equivalent on both sides of the interface.

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 10
    xmax = 0.1
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 10
    xmin = 0.1
    xmax = 0.2
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
  [interface_secondary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'fixed_block_left'
    new_block_id = 3
    new_block_name = 'interface_secondary_subdomain'
    input = block_rename
  []
  [interface_primary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'moving_block_right'
    new_block_id = 4
    new_block_name = 'interface_primary_subdomain'
    input = interface_secondary_subdomain
  []
[]

[Problem]
  type = ReferenceResidualProblem
  reference_vector = 'ref'
  extra_tag_vectors = 'ref'
[]

[Variables]
  [temperature]
    initial_condition = 300.0
  []
  [potential]
  []
  [potential_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[AuxVariables]
  [interface_normal_lm]
    order = FIRST
    family = LAGRANGE
    block = 'interface_secondary_subdomain'
    initial_condition = 1.0
  []
[]

[Kernels]
  [HeatDiff_steel]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = steel_thermal_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block'
  []
  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    extra_vector_tags = 'ref'
    block = 'right_block'
  []

  [electric_steel]
    type = ADMatDiffusion
    variable = potential
    diffusivity = steel_electrical_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block'
  []
  [electric_aluminum]
    type = ADMatDiffusion
    variable = potential
    diffusivity = aluminum_electrical_conductivity
    extra_vector_tags = 'ref'
    block = 'right_block'
  []
[]

[BCs]
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'fixed_block_right'
  []

  [electric_left]
    type = ADDirichletBC
    variable = potential
    value = 0.0
    boundary = moving_block_left
  []
  [electric_right]
    type = ADDirichletBC
    variable = potential
    value = 3.0e-1
    boundary = fixed_block_right
  []
[]

[Constraints]
  [electrical_contact]
    type = ModularGapConductanceConstraint
    variable = potential_interface_lm
    secondary_variable = potential
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed_electric'
  []
  [interface_heating]
    type = ADInterfaceJouleHeatingConstraint
    potential_lagrange_multiplier = potential_interface_lm
    secondary_variable = temperature
    primary_electrical_conductivity = steel_electrical_conductivity
    secondary_electrical_conductivity = aluminum_electrical_conductivity
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
  []
[]

[Materials]
  [steel_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'steel_density steel_thermal_conductivity steel_heat_capacity steel_electrical_conductivity         steel_hardness'
    prop_values = '8e3            16.2                        500.0              1.39e6      1.0' ## for stainless steel 304
    block = 'left_block interface_secondary_subdomain'
  []

  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density aluminum_thermal_conductivity aluminum_heat_capacity aluminum_electrical_conductivity aluminum_hardness'
    prop_values = ' 2.7e3           210                           900.0                   3.7e7                           1.0' #for 99% pure Al
    block = 'left_block right_block interface_secondary_subdomain'
  []
[]

[UserObjects]
  [closed_electric]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = steel_electrical_conductivity
    secondary_conductivity = aluminum_electrical_conductivity
    temperature = potential
    contact_pressure = interface_normal_lm
    primary_hardness = steel_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
[]

[Postprocessors]
  [steel_interface_temperature]
    type = AverageNodalVariableValue
    variable = temperature
    block = interface_primary_subdomain
  []
  [aluminum_interface_temperature]
    type = AverageNodalVariableValue
    variable = temperature
    block = interface_secondary_subdomain
  []
  [interface_heat_flux_steel]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = moving_block_right
    diffusivity = steel_thermal_conductivity
  []
  [interface_heat_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = fixed_block_left
    diffusivity = aluminum_thermal_conductivity
  []
  [interface_electrical_flux]
    type = ADSideDiffusiveFluxAverage
    variable = potential
    boundary = fixed_block_left
    diffusivity = aluminum_electrical_conductivity
  []
[]

[Executioner]
  type = Steady
  solve_type = NEWTON
  automatic_scaling = false
  line_search = 'none'

  nl_abs_tol = 1e-10
  nl_rel_tol = 1e-6
  nl_max_its = 100
  nl_forced_its = 1
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/large_gap_heat_transfer_test_cylinder_mortar_error.i)

rpv_core_gap_size = 0.15

core_outer_radius = 2
rpv_inner_radius = ${fparse 2 + rpv_core_gap_size}
rpv_outer_radius = ${fparse 2.5 + rpv_core_gap_size}

rpv_outer_htc = 10 # W/m^2/K
rpv_outer_Tinf = 300 # K

core_blocks = '1'
rpv_blocks = '3'

[Mesh]
  [core_gap_rpv]
    type = ConcentricCircleMeshGenerator
    num_sectors = 10
    radii = '${core_outer_radius} ${rpv_inner_radius} ${rpv_outer_radius}'
    rings = '2 1 2'
    has_outer_square = false
    preserve_volumes = true
    portion = full
  []
  [rename_core_bdy]
    type = SideSetsBetweenSubdomainsGenerator
    input = core_gap_rpv
    primary_block = 1
    paired_block = 2
    new_boundary = 'core_outer'
  []
  [rename_inner_rpv_bdy]
    type = SideSetsBetweenSubdomainsGenerator
    input = rename_core_bdy
    primary_block = 3
    paired_block = 2
    new_boundary = 'rpv_inner'
  []
  [2d_mesh]
    type = BlockDeletionGenerator
    input = rename_inner_rpv_bdy
    block = 2
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'rpv_inner'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = 2d_mesh
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'core_outer'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  allow_renumbering = false
[]

[Variables]
  [Tsolid]
    initial_condition = 500
  []
  [lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[Kernels]
  [heat_source]
    type = CoupledForce
    variable = Tsolid
    block = '${core_blocks}'
    v = power_density
  []
  [heat_conduction]
    type = HeatConduction
    variable = Tsolid
  []
[]

[BCs]
  [RPV_out_BC] # k \nabla T = h (T- T_inf) at RPV outer boundary
    type = ConvectiveFluxFunction # (Robin BC)
    variable = Tsolid
    boundary = 'outer' # outer RPV
    coefficient = ${rpv_outer_htc}
    T_infinity = ${rpv_outer_Tinf}
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    temperature = Tsolid
    boundary = 'rpv_inner'
    primary_emissivity = 0.8
    secondary_emissivity = 0.8
  []
  [conduction]
    type = GapFluxModelConduction
    temperature = Tsolid
    boundary = 'rpv_inner'
    gap_conductivity = 0.1
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = Tsolid
    primary_boundary = 'core_outer'
    primary_subdomain = 10000
    secondary_boundary = 'rpv_inner'
    secondary_subdomain = 10001
    gap_flux_models = 'radiation conduction'
    gap_geometry_type = 'CYLINDER'
    cylinder_axis_point_2 = '0 0 5'
  []
[]

[AuxVariables]
  [power_density]
    block = '${core_blocks}'
    initial_condition = 50e3
  []
[]

[Materials]
  [simple_mat]
    type = HeatConductionMaterial
    thermal_conductivity = 34.6 # W/m/K
  []
[]

[Postprocessors]
  [Tcore_avg]
    type = ElementAverageValue
    variable = Tsolid
    block = '${core_blocks}'
  []
  [Tcore_max]
    type = ElementExtremeValue
    value_type = max
    variable = Tsolid
    block = '${core_blocks}'
  []
  [Tcore_min]
    type = ElementExtremeValue
    value_type = min
    variable = Tsolid
    block = '${core_blocks}'
  []
  [Trpv_avg]
    type = ElementAverageValue
    variable = Tsolid
    block = '${rpv_blocks}'
  []
  [Trpv_max]
    type = ElementExtremeValue
    value_type = max
    variable = Tsolid
    block = '${rpv_blocks}'
  []
  [Trpv_min]
    type = ElementExtremeValue
    value_type = min
    variable = Tsolid
    block = '${rpv_blocks}'
  []
  [ptot]
    type = ElementIntegralVariablePostprocessor
    variable = power_density
    block = '${core_blocks}'
  []
  [rpv_convective_out]
    type = ConvectiveHeatTransferSideIntegral
    T_solid = Tsolid
    boundary = 'outer' # outer RVP
    T_fluid = ${rpv_outer_Tinf}
    htc = ${rpv_outer_htc}
  []
  [heat_balance] # should be equal to 0 upon convergence
    type = ParsedPostprocessor
    expression = '(rpv_convective_out - ptot) / ptot'
    pp_names = 'rpv_convective_out ptot'
  []
[]

[Preconditioning]
  [smp]
    type = SMP
    full = true
  []
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = 'rpv_inner core_outer'
    variable = 'Tsolid'
  []
[]

[Executioner]
  type = Steady

  petsc_options = '-snes_converged_reason -pc_svd_monitor'
  petsc_options_iname = '-pc_type -pc_factor_mat_solver_package -mat_mffd_err -pc_factor_shift_type '
                        '-pc_factor_shift_amount'
  petsc_options_value = ' lu       superlu_dist                  1e-5          NONZERO               '
                        '1e-15'
  snesmf_reuse_base = false

  nl_rel_tol = 1e-10
  nl_abs_tol = 1e-10
  l_max_its = 100

  line_search = none
[]

[Outputs]
  exodus = false
  csv = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced_radiation_conduction.i)

[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [file]
    type = FileMeshGenerator
    file = 2blk-gap.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '101'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '100'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  allow_renumbering = false
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Variables]
  [temp]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_x]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_y]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[Materials]
  [left]
    type = ADHeatConductionMaterial
    block = 1
    thermal_conductivity = 0.01
    specific_heat = 1
  []

  [right]
    type = ADHeatConductionMaterial
    block = 2
    thermal_conductivity = 0.005
    specific_heat = 1
  []
[]

[Kernels]
  [hc_displaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = true
    block = '1'
  []
  [hc_undisplaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = false
    block = '2'
  []
  [disp_x]
    type = Diffusion
    variable = disp_x
    block = '1 2'
  []
  [disp_y]
    type = Diffusion
    variable = disp_y
    block = '1 2'
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    temperature = temp
    boundary = 100
    primary_emissivity = 1.0
    secondary_emissivity = 1.0
    use_displaced_mesh = true
  []
  [conduction]
    type = GapFluxModelConduction
    temperature = temp
    boundary = 100
    gap_conductivity = 0.02
    use_displaced_mesh = true
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    use_displaced_mesh = true
    primary_boundary = 100
    primary_subdomain = 10000
    secondary_boundary = 101
    secondary_subdomain = 10001
    gap_flux_models = 'radiation conduction'
  []
[]

[BCs]
  [left]
    type = DirichletBC
    variable = temp
    boundary = 'left'
    value = 100
  []

  [right]
    type = DirichletBC
    variable = temp
    boundary = 'right'
    value = 0
  []

  [left_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'left'
    value = .1
  []
  [right_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'right'
    value = 0
  []
  [bottom_disp_y]
    type = DirichletBC
    preset = false
    variable = disp_y
    boundary = 'bottom'
    value = 0
  []
[]

[Preconditioning]
  [fmp]
    type = SMP
    full = true
    solve_type = 'NEWTON'
  []
[]

[Executioner]
  type = Steady
  nl_rel_tol = 1e-11
  nl_abs_tol = 1.0e-10
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = '100 101'
    variable = 'temp'
  []
[]

[Outputs]
  exodus = false
  csv = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced_radiation_conduction_separate.i)

[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [file]
    type = FileMeshGenerator
    file = 2blk-gap.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '101'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '100'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  allow_renumbering = false
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Variables]
  [temp]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_x]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_y]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  []
  [lm_conduction]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[Materials]
  [left]
    type = ADHeatConductionMaterial
    block = 1
    thermal_conductivity = 0.01
    specific_heat = 1
  []

  [right]
    type = ADHeatConductionMaterial
    block = 2
    thermal_conductivity = 0.005
    specific_heat = 1
  []
[]

[Kernels]
  [hc_displaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = true
    block = '1'
  []
  [hc_undisplaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = false
    block = '2'
  []
  [disp_x]
    type = Diffusion
    variable = disp_x
    block = '1 2'
  []
  [disp_y]
    type = Diffusion
    variable = disp_y
    block = '1 2'
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    temperature = temp
    boundary = 100
    primary_emissivity = 1.0
    secondary_emissivity = 1.0
    use_displaced_mesh = true
  []
  [conduction]
    type = GapFluxModelConduction
    temperature = temp
    boundary = 100
    gap_conductivity = 0.02
    use_displaced_mesh = true
  []
[]

[Constraints]
  [ced_radiation]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    use_displaced_mesh = true
    primary_boundary = 100
    primary_subdomain = 10000
    secondary_boundary = 101
    secondary_subdomain = 10001
    gap_flux_models = 'radiation'
  []
  [ced_conduction]
    type = ModularGapConductanceConstraint
    variable = lm_conduction
    secondary_variable = temp
    use_displaced_mesh = true
    primary_boundary = 100
    primary_subdomain = 10000
    secondary_boundary = 101
    secondary_subdomain = 10001
    gap_flux_models = 'conduction'
  []
[]

[BCs]
  [left]
    type = DirichletBC
    variable = temp
    boundary = 'left'
    value = 100
  []

  [right]
    type = DirichletBC
    variable = temp
    boundary = 'right'
    value = 0
  []

  [left_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'left'
    value = .1
  []
  [right_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'right'
    value = 0
  []
  [bottom_disp_y]
    type = DirichletBC
    preset = false
    variable = disp_y
    boundary = 'bottom'
    value = 0
  []
[]

[Preconditioning]
  [fmp]
    type = SMP
    full = true
    solve_type = 'NEWTON'
  []
[]

[Executioner]
  type = Steady
  nl_rel_tol = 1e-11
  nl_abs_tol = 1.0e-10
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = '100 101'
    variable = 'temp'
  []
[]

[Outputs]
  exodus = false
  csv = true
[]

(modules/combined/test/tests/gap_heat_transfer_mortar/small-2d/closed_gap_pressure_dependent_thermal_contact.i)

## Units in the input file: m-Pa-s-K

# The analytical solution for a steady state thermal contact and a mechanical
# contact pressure of 1Pa, the temperature of the steel block at the interface
# is calcaluated as
#
# T^s_{int} = \frac{T^a_{BC}C_T k_a + T^s_{BC} k_s \left(k_a +C_T \right)}{k_s (k_a + C_T) + k_a C_T}
# T^s_{int} = 460K
#
# with the boundary conditions and thermal conductivity values specified in the
# input file below. Similarly, the temperature of the aluminum block (cold block)
# is calculated as
#
# T^a_{int} = \frac{T^s_{int} C_T + T^a_{BC} k_a}{k_a + C_T}
# T^a_{int} = 276K
#
# The values predicted by the simulation at the interface converge towards these
# temperature values, and are within a few degrees by 240s. A smaller timestep
# than is practical for the regression test application further reduces the difference
# between the analytical solution and the simulation result.


[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 40
    ny = 10
    xmax = 1
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 40
    ny = 10
    xmin = 1
    xmax = 2
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
[]

[Variables]
  [disp_x]
    block = 'left_block right_block'
  []
  [disp_y]
    block = 'left_block right_block'
  []
  [temperature]
    initial_condition = 525.0
  []
  [temperature_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[Physics]
  [SolidMechanics/QuasiStatic]
    [steel]
      strain = SMALL
      add_variables = false
      use_automatic_differentiation = true
      additional_generate_output = 'vonmises_stress'
      additional_material_output_family = 'MONOMIAL'
      additional_material_output_order = 'FIRST'
      block = 'left_block'
    []
    [aluminum]
      strain = SMALL
      add_variables = false
      use_automatic_differentiation = true
      additional_generate_output = 'vonmises_stress'
      additional_material_output_family = 'MONOMIAL'
      additional_material_output_order = 'FIRST'
      block = 'right_block'
    []
  []
[]

[Kernels]
  [HeatDiff_steel]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = steel_thermal_conductivity
    block = 'left_block'
  []
  [HeatTdot_steel]
    type = ADHeatConductionTimeDerivative
    variable = temperature
    specific_heat = steel_heat_capacity
    density_name = steel_density
    block = 'left_block'
  []
  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    block = 'right_block'
  []
  [HeatTdot_aluminum]
    type = ADHeatConductionTimeDerivative
    variable = temperature
    specific_heat = aluminum_heat_capacity
    density_name = aluminum_density
    block = 'right_block'
  []
[]

[BCs]
  [fixed_bottom_edge]
    type = ADDirichletBC
    variable = disp_y
    value = 0
    boundary = 'moving_block_bottom fixed_block_bottom'
  []
  [fixed_outer_edge]
    type = ADDirichletBC
    variable = disp_x
    value = 0
    boundary = 'fixed_block_right'
  []
  [displacement_left_block]
    type = ADDirichletBC
    variable = disp_x
    value = 1.8e-11
    boundary = 'moving_block_left'
  []
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 800
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 250
    boundary = 'fixed_block_right'
  []
[]

[Contact]
  [interface]
    primary = moving_block_right
    secondary = fixed_block_left
    model = frictionless
    formulation = mortar
    correct_edge_dropping = true
  []
[]

[Constraints]
  [thermal_contact]
    type = ModularGapConductanceConstraint
    variable = temperature_interface_lm
    secondary_variable = temperature
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed'
    use_displaced_mesh = true
  []
[]

[Materials]
  [steel_elasticity_tensor]
    type = ADComputeIsotropicElasticityTensor
    youngs_modulus = 1.93e11 #in Pa, 193 GPa, stainless steel 304
    poissons_ratio = 0.29
    block = 'left_block'
  []
  [steel_stress]
    type = ADComputeLinearElasticStress
    block = 'left_block'
  []
  [steel_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'steel_density steel_thermal_conductivity steel_heat_capacity'
    prop_values = '8e3            16.2                        0.5' ## for stainless steel 304
    block = 'left_block'
  []

  [aluminum_elasticity_tensor]
    type = ADComputeIsotropicElasticityTensor
    youngs_modulus = 6.8e10 #in Pa, 68 GPa, aluminum
    poissons_ratio = 0.36
    block = 'right_block'
  []
  [aluminum_stress]
    type = ADComputeLinearElasticStress
    block = 'right_block'
  []
  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density aluminum_thermal_conductivity aluminum_heat_capacity'
    prop_values = ' 2.7e3           210                             0.9'
    block = 'right_block'
  []
[]

[UserObjects]
  [closed]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = steel_thermal_conductivity
    secondary_conductivity = aluminum_thermal_conductivity
    temperature = temperature
    contact_pressure = interface_normal_lm
    primary_hardness = 1.0
    secondary_hardness = 1.0
    boundary = moving_block_right
  []
[]

[Postprocessors]
  [steel_pt_interface_temperature]
    type = NodalVariableValue
    nodeid = 245
    variable = temperature
  []
  [aluminum_pt_interface_temperature]
    type = NodalVariableValue
    nodeid = 657
    variable = temperature
  []
  [interface_heat_flux_steel]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = moving_block_right
    diffusivity = steel_thermal_conductivity
  []
  [interface_heat_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = fixed_block_left
    diffusivity = aluminum_thermal_conductivity
  []
[]


[Executioner]
  type = Transient
  solve_type = NEWTON
  automatic_scaling = false
  line_search = 'none'

  # mortar contact solver options
  petsc_options = '-snes_converged_reason -pc_svd_monitor'
  petsc_options_iname = '-pc_type -pc_factor_mat_solver_type'
  petsc_options_value = ' lu       superlu_dist'
  snesmf_reuse_base = false

  nl_rel_tol = 1e-10
  nl_max_its = 20
  l_max_its = 50

  dt = 60
  end_time = 240
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar_action/modular_gap_heat_transfer_mortar_displaced_radiation_conduction_verbose.i)

[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [file]
    type = FileMeshGenerator
    file = 2blk-gap.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '101'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '100'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  allow_renumbering = false
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Variables]
  [temp]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_x]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_y]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[Materials]
  [left]
    type = ADHeatConductionMaterial
    block = 1
    thermal_conductivity = 0.01
    specific_heat = 1
  []

  [right]
    type = ADHeatConductionMaterial
    block = 2
    thermal_conductivity = 0.005
    specific_heat = 1
  []
[]

[Kernels]
  [hc_displaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = true
    block = '1'
  []
  [hc_undisplaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = false
    block = '2'
  []
  [disp_x]
    type = Diffusion
    variable = disp_x
    block = '1 2'
  []
  [disp_y]
    type = Diffusion
    variable = disp_y
    block = '1 2'
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    temperature = temp
    boundary = 100
    primary_emissivity = 1.0
    secondary_emissivity = 1.0
    use_displaced_mesh = true
  []
  [conduction]
    type = GapFluxModelConduction
    temperature = temp
    boundary = 100
    gap_conductivity = 0.02
    use_displaced_mesh = true
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    use_displaced_mesh = true
    primary_boundary = 100
    primary_subdomain = 10000
    secondary_boundary = 101
    secondary_subdomain = 10001
    correct_edge_dropping = true
    gap_flux_models = 'radiation conduction'
  []
[]

[BCs]
  [left]
    type = DirichletBC
    variable = temp
    boundary = 'left'
    value = 100
  []

  [right]
    type = DirichletBC
    variable = temp
    boundary = 'right'
    value = 0
  []

  [left_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'left'
    value = .1
  []
  [right_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'right'
    value = 0
  []
  [bottom_disp_y]
    type = DirichletBC
    preset = false
    variable = disp_y
    boundary = 'bottom'
    value = 0
  []
[]

[Preconditioning]
  [fmp]
    type = SMP
    full = true
    solve_type = 'NEWTON'
  []
[]

[Executioner]
  type = Steady
  nl_rel_tol = 1e-11
  nl_abs_tol = 1.0e-10
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = '100 101'
    variable = 'temp'
  []
[]

[Outputs]
  csv = true
  [exodus]
    type = Exodus
    show = 'temp'
  []
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/large_gap_heat_transfer_test_rz_cylinder_mortar.i)

rpv_core_gap_size = 0.2

core_outer_radius = 2
rpv_inner_radius = '${fparse 2 + rpv_core_gap_size}'
rpv_outer_radius = '${fparse 2.5 + rpv_core_gap_size}'
rpv_width = '${fparse rpv_outer_radius - rpv_inner_radius}'

rpv_outer_htc = 10 # W/m^2/K
rpv_outer_Tinf = 300 # K

core_blocks = '1'
rpv_blocks = '3'

[Mesh]
  [gmg]
    type = CartesianMeshGenerator
    dim = 2
    dx = '${core_outer_radius} ${rpv_core_gap_size} ${rpv_width}'
    ix = '400 1 100'
    dy = 1
    iy = '5'
  []
  [set_block_id1]
    type = SubdomainBoundingBoxGenerator
    input = gmg
    bottom_left = '0 0 0'
    top_right = '${core_outer_radius} 1 0'
    block_id = 1
    location = INSIDE
  []
  [rename_core_bdy]
    type = SideSetsBetweenSubdomainsGenerator
    input = set_block_id1
    primary_block = 1
    paired_block = 0
    new_boundary = 'core_outer'
  []
  [set_block_id3]
    type = SubdomainBoundingBoxGenerator
    input = rename_core_bdy
    bottom_left = '${rpv_inner_radius} 0 0'
    top_right = '${rpv_outer_radius} 1 0'
    block_id = 3
    location = INSIDE
  []
  [rename_inner_rpv_bdy]
    type = SideSetsBetweenSubdomainsGenerator
    input = set_block_id3
    primary_block = 3
    paired_block = 0
    new_boundary = 'rpv_inner'
  []
  # comment out for test without gap
  [2d_mesh]
    type = BlockDeletionGenerator
    input = rename_inner_rpv_bdy
    block = 0
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'rpv_inner'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = 2d_mesh
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'core_outer'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  allow_renumbering = false
  coord_type = RZ
[]

[Variables]
  [Tsolid]
    initial_condition = 500
  []
    [lm]
      order = FIRST
      family = LAGRANGE
      block = 'secondary_lower'
    []
[]

[Kernels]
  [heat_source]
    type = CoupledForce
    variable = Tsolid
    block = '${core_blocks}'
    v = power_density
  []
  [heat_conduction]
    type = HeatConduction
    variable = Tsolid
  []
[]

[BCs]
  [RPV_out_BC] # k \nabla T = h (T- T_inf) at RPV outer boundary
    type = ConvectiveFluxFunction # (Robin BC)
    variable = Tsolid
    boundary = 'right' # outer RPV
    coefficient = ${rpv_outer_htc}
    T_infinity = ${rpv_outer_Tinf}
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    temperature = Tsolid
    boundary = 'rpv_inner'
    primary_emissivity = 0.8
    secondary_emissivity = 0.8
  []
  [conduction]
    type = GapFluxModelConduction
    temperature = Tsolid
    boundary = 'rpv_inner'
    gap_conductivity = 0.1
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = Tsolid
    primary_boundary = 'core_outer'
    primary_subdomain = 10000
    secondary_boundary = 'rpv_inner'
    secondary_subdomain = 10001
    gap_flux_models = 'radiation conduction'
    gap_geometry_type = 'CYLINDER'
  []
[]

[AuxVariables]
  [power_density]
    block = '${core_blocks}'
    initial_condition = 50e3
  []
[]

[Materials]
  [simple_mat]
    type = HeatConductionMaterial
    thermal_conductivity = 34.6 # W/m/K
  []
[]

[Postprocessors]
  [Tcore_avg]
    type = ElementAverageValue
    variable = Tsolid
    block = '${core_blocks}'
  []
  [Tcore_max]
    type = ElementExtremeValue
    value_type = max
    variable = Tsolid
    block = '${core_blocks}'
  []
  [Tcore_min]
    type = ElementExtremeValue
    value_type = min
    variable = Tsolid
    block = '${core_blocks}'
  []
  [Trpv_avg]
    type = ElementAverageValue
    variable = Tsolid
    block = '${rpv_blocks}'
  []
  [Trpv_max]
    type = ElementExtremeValue
    value_type = max
    variable = Tsolid
    block = '${rpv_blocks}'
  []
  [Trpv_min]
    type = ElementExtremeValue
    value_type = min
    variable = Tsolid
    block = '${rpv_blocks}'
  []
  [ptot]
    type = ElementIntegralVariablePostprocessor
    variable = power_density
    block = '${core_blocks}'
  []
  [rpv_convective_out]
    type = ConvectiveHeatTransferSideIntegral
    T_solid = Tsolid
    boundary = 'right' # outer RVP
    T_fluid = ${rpv_outer_Tinf}
    htc = ${rpv_outer_htc}
  []
  [heat_balance] # should be equal to 0 upon convergence
    type = ParsedPostprocessor
    expression = '(rpv_convective_out - ptot) / ptot'
    pp_names = 'rpv_convective_out ptot'
  []
  [flux_from_core] # converges to ptot as the mesh is refined
    type = SideDiffusiveFluxIntegral
    variable = Tsolid
    boundary = core_outer
    diffusivity = thermal_conductivity
  []
  [flux_into_rpv] # converges to rpv_convective_out as the mesh is refined
    type = SideDiffusiveFluxIntegral
    variable = Tsolid
    boundary = rpv_inner
    diffusivity = thermal_conductivity
  []

[]

[Preconditioning]
  [smp]
    type = SMP
    full = true
  []
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = 'rpv_inner core_outer'
    variable = Tsolid
  []
[]

[Executioner]
  type = Steady

  petsc_options = '-snes_converged_reason -pc_svd_monitor'
  petsc_options_iname = '-pc_type -pc_factor_mat_solver_package -mat_mffd_err -pc_factor_shift_type '
                        '-pc_factor_shift_amount'
  petsc_options_value = ' lu       superlu_dist                  1e-5          NONZERO               '
                        '1e-15'
  snesmf_reuse_base = false
  nl_rel_tol = 1e-10
  nl_abs_tol = 1e-10
  l_max_its = 100

  line_search = none
[]

[Outputs]
  exodus = false
  csv = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced_conduction_function.i)

[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [file]
    type = FileMeshGenerator
    file = 2blk-gap.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '101'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '100'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  allow_renumbering = false
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[AuxVariables]
  [dummy]
    order = FIRST
    family = LAGRANGE
    initial_condition = 1.0
  []
[]

[Functions]
  [function]
    type = ParsedFunction
      expression = 'if(t > 100.0, 0.0, t)'
  []
[]

[Variables]
  [temp]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_x]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_y]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[Materials]
  [left]
    type = ADHeatConductionMaterial
    block = 1
    thermal_conductivity = 0.01
    specific_heat = 1
  []

  [right]
    type = ADHeatConductionMaterial
    block = 2
    thermal_conductivity = 0.005
    specific_heat = 1
  []
[]

[Kernels]
  [hc_displaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = true
    block = '1'
  []
  [hc_undisplaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = false
    block = '2'
  []
  [disp_x]
    type = Diffusion
    variable = disp_x
    block = '1 2'
  []
  [disp_y]
    type = Diffusion
    variable = disp_y
    block = '1 2'
  []
[]

[UserObjects]
  [conduction]
    type = GapFluxModelConduction
    temperature = temp
    boundary = 100
    gap_conductivity = 10.0
    gap_conductivity_function_variable = dummy
    gap_conductivity_function = function
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    use_displaced_mesh = true
    primary_boundary = 100
    primary_subdomain = 10000
    secondary_boundary = 101
    secondary_subdomain = 10001
    gap_flux_models = conduction
  []
[]

[BCs]
  [left]
    type = DirichletBC
    variable = temp
    boundary = 'left'
    value = 100
  []

  [right]
    type = DirichletBC
    variable = temp
    boundary = 'right'
    value = 0
  []

  [left_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'left'
    value = .1
  []
  [right_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'right'
    value = 0
  []
  [bottom_disp_y]
    type = DirichletBC
    preset = false
    variable = disp_y
    boundary = 'bottom'
    value = 0
  []
[]

[Preconditioning]
  [fmp]
    type = SMP
    full = true
    solve_type = 'NEWTON'
  []
[]

[Executioner]
  type = Steady
  nl_rel_tol = 1e-11
  nl_abs_tol = 1.0e-10
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = '100 101'
    variable = 'temp'
  []
[]

[Outputs]
  exodus = false
  csv = true
[]

(modules/heat_transfer/test/tests/interface_heating_mortar/constraint_joule_heating_dual_material.i)

## Units in the input file: m-Pa-s-K-V

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 10
    xmax = 0.1
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 10
    xmin = 0.1
    xmax = 0.2
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
  [interface_secondary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'fixed_block_left'
    new_block_id = 3
    new_block_name = 'interface_secondary_subdomain'
    input = block_rename
  []
  [interface_primary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'moving_block_right'
    new_block_id = 4
    new_block_name = 'interface_primary_subdomain'
    input = interface_secondary_subdomain
  []
[]

[Problem]
  type = ReferenceResidualProblem
  reference_vector = 'ref'
  extra_tag_vectors = 'ref'
[]

[Variables]
  [temperature]
    initial_condition = 300.0
  []
  [temperature_interface_lm]
    block = 'interface_secondary_subdomain'
  []
  [potential]
  []
  [potential_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[AuxVariables]
  [interface_normal_lm]
    order = FIRST
    family = LAGRANGE
    block = 'interface_secondary_subdomain'
    initial_condition = 1.0
  []
[]

[Kernels]
  [HeatDiff_steel]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = steel_thermal_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block'
  []
  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    extra_vector_tags = 'ref'
    block = 'right_block'
  []
  [electric_steel]
    type = ADMatDiffusion
    variable = potential
    diffusivity = steel_electrical_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block'
  []
  [electric_aluminum]
    type = ADMatDiffusion
    variable = potential
    diffusivity = aluminum_electrical_conductivity
    extra_vector_tags = 'ref'
    block = 'right_block'
  []
[]

[BCs]
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'fixed_block_right'
  []

  [electric_left]
    type = ADDirichletBC
    variable = potential
    value = 0.0
    boundary = moving_block_left
  []
  [electric_right]
    type = ADDirichletBC
    variable = potential
    value = 3.0e-1
    boundary = fixed_block_right
  []
[]

[Constraints]
  [thermal_contact]
    type = ModularGapConductanceConstraint
    variable = temperature_interface_lm
    secondary_variable = temperature
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed_temperature'
  []
  [electrical_contact]
    type = ModularGapConductanceConstraint
    variable = potential_interface_lm
    secondary_variable = potential
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed_electric'
  []
  [interface_heating]
    type = ADInterfaceJouleHeatingConstraint
    potential_lagrange_multiplier = potential_interface_lm
    secondary_variable = temperature
    primary_electrical_conductivity = steel_electrical_conductivity
    secondary_electrical_conductivity = aluminum_electrical_conductivity
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
  []
[]

[Materials]
  [steel_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'steel_density steel_thermal_conductivity steel_heat_capacity steel_electrical_conductivity         steel_hardness'
    prop_values = '8e3            16.2                        500.0              1.39e6      1.0' ## for stainless steel 304
    block = 'left_block interface_secondary_subdomain'
  []

  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density aluminum_thermal_conductivity aluminum_heat_capacity aluminum_electrical_conductivity aluminum_hardness'
    prop_values = ' 2.7e3           210                           900.0                   3.7e7                           1.0' #for 99% pure Al
    block = 'left_block right_block interface_secondary_subdomain'
  []
[]

[UserObjects]
  [closed_temperature]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = steel_thermal_conductivity
    secondary_conductivity = aluminum_thermal_conductivity
    temperature = temperature
    contact_pressure = interface_normal_lm
    primary_hardness = steel_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
  [closed_electric]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = steel_electrical_conductivity
    secondary_conductivity = aluminum_electrical_conductivity
    temperature = potential
    contact_pressure = interface_normal_lm
    primary_hardness = steel_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
[]

[Postprocessors]
  [steel_interface_temperature]
    type = AverageNodalVariableValue
    variable = temperature
    block = interface_primary_subdomain
  []
  [aluminum_interface_temperature]
    type = AverageNodalVariableValue
    variable = temperature
    block = interface_secondary_subdomain
  []
  [interface_heat_flux_steel]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = moving_block_right
    diffusivity = steel_thermal_conductivity
  []
  [interface_heat_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = fixed_block_left
    diffusivity = aluminum_thermal_conductivity
  []

  [interface_electrical_flux]
    type = ADSideDiffusiveFluxAverage
    variable = potential
    boundary = fixed_block_left
    diffusivity = aluminum_electrical_conductivity
  []
[]

[Executioner]
  type = Steady
  solve_type = NEWTON
  automatic_scaling = false
  line_search = 'none'

  nl_abs_tol = 1e-10
  nl_rel_tol = 1e-6
  nl_max_its = 100
  nl_forced_its = 1
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/heat_transfer/test/tests/interface_heating_mortar/transient_joule_heating_constraint.i)

## Units in the input file: m-Pa-s-K-V

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 10
    xmax = 0.1
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 10
    xmin = 0.1
    xmax = 0.2
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
  [interface_secondary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'fixed_block_left'
    new_block_id = 3
    new_block_name = 'interface_secondary_subdomain'
    input = block_rename
  []
  [interface_primary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'moving_block_right'
    new_block_id = 4
    new_block_name = 'interface_primary_subdomain'
    input = interface_secondary_subdomain
  []
[]

[Problem]
  type = ReferenceResidualProblem
  reference_vector = 'ref'
  extra_tag_vectors = 'ref'
[]

[Variables]
  [temperature]
    initial_condition = 300.0
  []
  [temperature_interface_lm]
    block = 'interface_secondary_subdomain'
  []
  [potential]
  []
  [potential_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[AuxVariables]
  [interface_normal_lm]
    order = FIRST
    family = LAGRANGE
    block = 'interface_secondary_subdomain'
    initial_condition = 1.0
  []
[]

[Kernels]
  [HeatDiff_steel]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = steel_thermal_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block'
  []
  [HeatTdot_steel]
    type = ADHeatConductionTimeDerivative
    variable = temperature
    specific_heat = steel_heat_capacity #use parsed material property
    density_name = steel_density
    extra_vector_tags = 'ref'
    block = 'left_block'
  []

  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    extra_vector_tags = 'ref'
    block = 'right_block'
  []
  [HeatTdot_aluminum]
    type = ADHeatConductionTimeDerivative
    variable = temperature
    specific_heat = aluminum_heat_capacity #use parsed material property
    density_name = aluminum_density
    extra_vector_tags = 'ref'
    block = 'right_block'
  []

  [electric_steel]
    type = ADMatDiffusion
    variable = potential
    diffusivity = steel_electrical_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block'
  []
  [electric_aluminum]
    type = ADMatDiffusion
    variable = potential
    diffusivity = aluminum_electrical_conductivity
    extra_vector_tags = 'ref'
    block = 'right_block'
  []
[]

[BCs]
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'fixed_block_right'
  []

  [electric_left]
    type = ADDirichletBC
    variable = potential
    value = 0.0
    boundary = moving_block_left
  []
  [electric_right]
    type = ADDirichletBC
    variable = potential
    value = 3.0e-1
    boundary = fixed_block_right
  []
[]

[Constraints]
  [thermal_contact]
    type = ModularGapConductanceConstraint
    variable = temperature_interface_lm
    secondary_variable = temperature
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed_temperature'
  []
  [electrical_contact]
    type = ModularGapConductanceConstraint
    variable = potential_interface_lm
    secondary_variable = potential
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed_electric'
  []
  [interface_heating]
    type = ADInterfaceJouleHeatingConstraint
    potential_lagrange_multiplier = potential_interface_lm
    secondary_variable = temperature
    primary_electrical_conductivity = steel_electrical_conductivity
    secondary_electrical_conductivity = aluminum_electrical_conductivity
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
  []
[]

[Materials]
  [steel_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'steel_density steel_thermal_conductivity steel_heat_capacity steel_electrical_conductivity         steel_hardness'
    prop_values = '8e3            16.2                        500.0              1.39e6      1.0' ## for stainless steel 304
    block = 'left_block interface_secondary_subdomain'
  []

  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density aluminum_thermal_conductivity aluminum_heat_capacity aluminum_electrical_conductivity aluminum_hardness'
    prop_values = ' 2.7e3           210                           900.0                   3.7e7                           1.0' #for 99% pure Al
    block = 'left_block right_block interface_secondary_subdomain'
  []
[]

[UserObjects]
  [closed_temperature]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = steel_thermal_conductivity
    secondary_conductivity = aluminum_thermal_conductivity
    temperature = temperature
    contact_pressure = interface_normal_lm
    primary_hardness = steel_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
  [closed_electric]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = steel_electrical_conductivity
    secondary_conductivity = aluminum_electrical_conductivity
    temperature = potential
    contact_pressure = interface_normal_lm
    primary_hardness = steel_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
[]

[Postprocessors]
  [steel_interface_temperature]
    type = AverageNodalVariableValue
    variable = temperature
    block = interface_primary_subdomain
  []
  [aluminum_interface_temperature]
    type = AverageNodalVariableValue
    variable = temperature
    block = interface_secondary_subdomain
  []
  [interface_heat_flux_steel]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = moving_block_right
    diffusivity = steel_thermal_conductivity
  []
  [interface_heat_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = fixed_block_left
    diffusivity = aluminum_thermal_conductivity
  []

  [interface_electrical_flux]
    type = ADSideDiffusiveFluxAverage
    variable = potential
    boundary = fixed_block_left
    diffusivity = aluminum_electrical_conductivity
  []
[]

[Executioner]
  type = Transient
  solve_type = NEWTON
  automatic_scaling = false
  line_search = 'none'

  nl_abs_tol = 1e-8
  nl_rel_tol = 1e-4
  nl_max_its = 100
  nl_forced_its = 1

  dt = 1200.0
  dtmin = 1200.0
  num_steps = 8
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced.i)

[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [file]
    type = FileMeshGenerator
    file = 2blk-gap.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '101'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '100'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Variables]
  [./temp]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  [../]
  [./disp_x]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  [../]
  [./disp_y]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  [../]

  [./lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  [../]
[]

[Materials]
  [./left]
    type = ADHeatConductionMaterial
    block = 1
    thermal_conductivity = 1000
    specific_heat = 1
  [../]

  [./right]
    type = ADHeatConductionMaterial
    block = 2
    thermal_conductivity = 500
    specific_heat = 1
  [../]
[]

[Kernels]
  [./hc_displaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = true
    block = '1'
  [../]
  [./hc_undisplaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = false
    block = '2'
  [../]
  [disp_x]
    type = Diffusion
    variable = disp_x
    block = '1 2'
  []
  [disp_y]
    type = Diffusion
    variable = disp_y
    block = '1 2'
  []
[]

[UserObjects]
  [simple]
    type = GapFluxModelSimple
    k = 100
    temperature = temp
    boundary = 100
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    use_displaced_mesh = true
    primary_boundary = 100
    primary_subdomain = 10000
    secondary_boundary = 101
    secondary_subdomain = 10001
    gap_flux_models = simple
  []
[]

[BCs]
  [./left]
    type = DirichletBC
    variable = temp
    boundary = 'left'
    value = 1
  [../]

  [./right]
    type = DirichletBC
    variable = temp
    boundary = 'right'
    value = 0
  [../]

  [left_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'left'
    value = .1
  []
  [right_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'right'
    value = 0
  []
  [bottom_disp_y]
    type = DirichletBC
    preset = false
    variable = disp_y
    boundary = 'bottom'
    value = 0
  []
[]

[Preconditioning]
  [./fmp]
    type = SMP
    full = true
    solve_type = 'NEWTON'
  [../]
[]

[Executioner]
  type = Steady
  nl_rel_tol = 1e-11
[]

[Outputs]
  exodus = true
  show = 'temp disp_x disp_y'
  [dof]
    type = DOFMap
    execute_on = 'initial'
  []
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced_conduction.i)

[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [file]
    type = FileMeshGenerator
    file = 2blk-gap.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '101'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '100'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  allow_renumbering = false
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Variables]
  [temp]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_x]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_y]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[Materials]
  [left]
    type = ADHeatConductionMaterial
    block = 1
    thermal_conductivity = 0.01
    specific_heat = 1
  []

  [right]
    type = ADHeatConductionMaterial
    block = 2
    thermal_conductivity = 0.005
    specific_heat = 1
  []
[]

[Kernels]
  [hc_displaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = true
    block = '1'
  []
  [hc_undisplaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = false
    block = '2'
  []
  [disp_x]
    type = Diffusion
    variable = disp_x
    block = '1 2'
  []
  [disp_y]
    type = Diffusion
    variable = disp_y
    block = '1 2'
  []
[]

[UserObjects]
  [conduction]
    type = GapFluxModelConduction
    temperature = temp
    boundary = 100
    gap_conductivity = 10.0
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    use_displaced_mesh = true
    primary_boundary = 100
    primary_subdomain = 10000
    secondary_boundary = 101
    secondary_subdomain = 10001
    gap_flux_models = conduction
  []
[]

[BCs]
  [left]
    type = DirichletBC
    variable = temp
    boundary = 'left'
    value = 100
  []

  [right]
    type = DirichletBC
    variable = temp
    boundary = 'right'
    value = 0
  []

  [left_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'left'
    value = .1
  []
  [right_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'right'
    value = 0
  []
  [bottom_disp_y]
    type = DirichletBC
    preset = false
    variable = disp_y
    boundary = 'bottom'
    value = 0
  []
[]

[Preconditioning]
  [fmp]
    type = SMP
    full = true
    solve_type = 'NEWTON'
  []
[]

[Executioner]
  type = Steady
  nl_rel_tol = 1e-11
  nl_abs_tol = 1.0e-10
[]


[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = '100 101'
    variable = 'temp'
  []
[]

[Outputs]
  exodus = false
  csv = true
[]

(modules/heat_transfer/test/tests/interface_heating_mortar/constraint_joule_heating_offset_single_material_insulated.i)

## Units in the input file: m-Pa-s-K-V

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 100
    xmax = 0.1
    ymin = 0.1
    ymax = 0.35
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 100
    xmin = 0.1
    xmax = 0.2
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
  [interface_secondary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'fixed_block_left'
    new_block_id = 3
    new_block_name = 'interface_secondary_subdomain'
    input = block_rename
  []
  [interface_primary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'moving_block_right'
    new_block_id = 4
    new_block_name = 'interface_primary_subdomain'
    input = interface_secondary_subdomain
  []
[]

[Problem]
  type = ReferenceResidualProblem
  reference_vector = 'ref'
  extra_tag_vectors = 'ref'
[]

[Variables]
  [temperature]
    initial_condition = 300.0
  []
  [potential]
  []
  [potential_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[AuxVariables]
  [interface_normal_lm]
    order = FIRST
    family = LAGRANGE
    block = 'interface_secondary_subdomain'
    initial_condition = 1.0
  []
[]

[Kernels]
  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block right_block'
  []
  [electric_aluminum]
    type = ADMatDiffusion
    variable = potential
    diffusivity = aluminum_electrical_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block right_block'
  []
[]

[BCs]
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'fixed_block_right'
  []

  [electric_left]
    type = ADDirichletBC
    variable = potential
    value = 0.0
    boundary = moving_block_left
  []
  [electric_right]
    type = ADDirichletBC
    variable = potential
    value = 3.0e-1
    boundary = fixed_block_right
  []
[]

[Constraints]
  [electrical_contact]
    type = ModularGapConductanceConstraint
    variable = potential_interface_lm
    secondary_variable = potential
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed_electric'
    correct_edge_dropping = true
  []
  [interface_heating]
    type = ADInterfaceJouleHeatingConstraint
    potential_lagrange_multiplier = potential_interface_lm
    secondary_variable = temperature
    primary_electrical_conductivity = aluminum_electrical_conductivity
    secondary_electrical_conductivity = aluminum_electrical_conductivity
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
  []
[]

[Materials]
  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density aluminum_thermal_conductivity aluminum_heat_capacity aluminum_electrical_conductivity aluminum_hardness'
    prop_values = ' 2.7e3           210                           900.0                   3.7e7                           1.0' #for 99% pure Al
    block = 'left_block right_block interface_secondary_subdomain'
  []
[]

[UserObjects]
  [closed_electric]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = aluminum_electrical_conductivity
    secondary_conductivity = aluminum_electrical_conductivity
    temperature = potential
    contact_pressure = interface_normal_lm
    primary_hardness = aluminum_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
[]

[Postprocessors]
  [interface_heat_flux_large_block]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = fixed_block_left
    diffusivity = aluminum_thermal_conductivity
  []
  [interface_heat_flux_small_block]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = moving_block_right
    diffusivity = aluminum_thermal_conductivity
  []
  [interface_electrical_flux_large_block]
    type = ADSideDiffusiveFluxAverage
    variable = potential
    boundary = fixed_block_left
    diffusivity = aluminum_electrical_conductivity
  []
  [interface_electrical_flux_small_block]
    type = ADSideDiffusiveFluxAverage
    variable = potential
    boundary = moving_block_right
    diffusivity = aluminum_electrical_conductivity
  []
[]

[Executioner]
  type = Steady
  solve_type = NEWTON
  automatic_scaling = false
  line_search = 'none'

  nl_abs_tol = 2e-10
  nl_rel_tol = 1e-6
  nl_max_its = 50
  nl_forced_its = 1
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/closed_gap_prescribed_pressure.i)

## Units in the input file: m-Pa-s-K

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 40
    ny = 10
    xmax = 1
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 40
    ny = 10
    xmin = 1
    xmax = 2
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
  [interface_secondary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'fixed_block_left'
    new_block_id = 3
    new_block_name = 'interface_secondary_subdomain'
    input = block_rename
  []
  [interface_primary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'moving_block_right'
    new_block_id = 4
    new_block_name = 'interface_primary_subdomain'
    input = interface_secondary_subdomain
  []
[]

[Variables]
  [temperature]
    initial_condition = 525.0
  []
  [temperature_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[AuxVariables]
  [interface_normal_lm]
    order = FIRST
    family = LAGRANGE
    block = 'interface_secondary_subdomain'
    initial_condition = 100.0
  []
[]

[Kernels]
  [HeatDiff_steel]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = steel_thermal_conductivity
    block = 'left_block'
  []
  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    block = 'right_block'
  []
[]

[BCs]
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 800
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 250
    boundary = 'fixed_block_right'
  []
[]

[Constraints]
  [thermal_contact]
    type = ModularGapConductanceConstraint
    variable = temperature_interface_lm
    secondary_variable = temperature
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed'
  []
[]

[Materials]
  [steel_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'steel_density steel_thermal_conductivity steel_hardness'
    prop_values = '8e3            16.2                       129' ## for stainless steel 304
    block = 'left_block'
  []

  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density aluminum_thermal_conductivity aluminum_hardness'
    prop_values = ' 2.7e3           210                             15' #for 99% pure Al
    block = 'right_block'
  []
[]

[UserObjects]
  [closed]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = steel_thermal_conductivity
    secondary_conductivity = aluminum_thermal_conductivity
    temperature = temperature
    contact_pressure = interface_normal_lm
    primary_hardness = steel_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
[]

[Postprocessors]
  [steel_interface_temperature]
    type = AverageNodalVariableValue
    variable = temperature
    block = interface_primary_subdomain
  []
  [aluminum_interface_temperature]
    type = AverageNodalVariableValue
    variable = temperature
    block = interface_secondary_subdomain
  []
  [interface_heat_flux_steel]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = moving_block_right
    diffusivity = steel_thermal_conductivity
  []
  [interface_heat_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = fixed_block_left
    diffusivity = aluminum_thermal_conductivity
  []
[]


[Executioner]
  type = Steady
  solve_type = NEWTON
  automatic_scaling = false

  nl_rel_tol = 1e-14
  nl_max_its = 20
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/gap_heat_transfer_3D_mortar.i)

outer_htc = 10 # W/m^2/K
outer_Tinf = 300 # K

[GlobalParams]
  order = SECOND
  family = LAGRANGE
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Mesh]
  [left_block]
    type = GeneratedMeshGenerator
    dim = 3
    nx = 3
    ny = 6
    nz = 6
    xmin = -1
    xmax = -0.5
    ymin = -0.5
    ymax = 0.5
    zmin = -0.5
    zmax = 0.5
    elem_type = HEX27
  []
  [left_block_sidesets]
    type = RenameBoundaryGenerator
    input = left_block
    old_boundary = '0 1 2 3 4 5'
    new_boundary = 'left_bottom left_back left_right left_front left_left left_top'
  []
  [left_block_id]
    type = SubdomainIDGenerator
    input = left_block_sidesets
    subdomain_id = 1
  []

  [right_block]
    type = GeneratedMeshGenerator
    dim = 3
    nx = 4
    ny = 8
    nz = 8
    xmin = 0.5
    xmax = 1
    ymin = -0.5
    ymax = 0.5
    zmin = -0.5
    zmax = 0.5
    elem_type = HEX27
  []
  [right_block_sidesets]
    type = RenameBoundaryGenerator
    input = right_block
    old_boundary = '0 1 2 3 4 5'
    # new_boundary = 'right_bottom right_back right_right right_front right_left right_top'
    new_boundary = '100 101 102 103 104 105'
  []
  [right_block_sidesets_rename]
    type = RenameBoundaryGenerator
    input = right_block_sidesets
    old_boundary = '100 101 102 103 104 105'
    new_boundary = 'right_bottom right_back right_right right_front right_left right_top'
  []
  [right_block_id]
    type = SubdomainIDGenerator
    input = right_block_sidesets_rename
    subdomain_id = 2
  []

  [combined_mesh]
    type = MeshCollectionGenerator
    inputs = 'left_block_id right_block_id'
  []

  [left_lower]
    type = LowerDBlockFromSidesetGenerator
    input = combined_mesh
    sidesets = 'left_right'
    new_block_id = '10001'
    new_block_name = 'secondary_lower'
  []
  [right_lower]
    type = LowerDBlockFromSidesetGenerator
    input = left_lower
    sidesets = 'right_left'
    new_block_id = '10000'
    new_block_name = 'primary_lower'
  []
[]

[Functions]
  [temp]
    type = PiecewiseLinear
    x = '0   1'
    y = '100 200'
  []
[]

[Variables]
  [temp]
    initial_condition = 500
  []
  [lm]
    order = SECOND
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[AuxVariables]
  [power_density]
    block = 1
    initial_condition = 50e3
  []
[]

[Kernels]
  [heat_conduction]
    type = HeatConduction
    variable = temp
    block = '1 2'
  []
  [heat_source]
    type = CoupledForce
    variable = temp
    block = '1'
    v = power_density
  []
[]

[Materials]
  [heat1]
    type = HeatConductionMaterial
    block = '1 2'
    specific_heat = 1.0
    thermal_conductivity = 34.6
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    temperature = temp
    boundary = 'left_right'
    primary_emissivity = 0.0
    secondary_emissivity = 0.0
  []
  [conduction]
    type = GapFluxModelConduction
    temperature = temp
    boundary = 'left_right'
    gap_conductivity = 5.0
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    primary_boundary = 'right_left'
    primary_subdomain = 'primary_lower'
    secondary_boundary = 'left_right'
    secondary_subdomain = 'secondary_lower'
    gap_flux_models = 'radiation conduction'
    gap_geometry_type = PLATE
  []
[]

[BCs]
  [RPV_out_BC] # k \nabla T = h (T- T_inf) at RPV outer boundary
    type = ConvectiveFluxFunction # (Robin BC)
    variable = temp
    boundary = 'right_right' # outer RPV
    coefficient = ${outer_htc}
    T_infinity = ${outer_Tinf}
  []
[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_factor_mat_solver_package'
  petsc_options_value = 'lu       superlu_dist'

  dt = 1
  dtmin = 0.01
  end_time = 1

  nl_rel_tol = 1e-12
  nl_abs_tol = 1e-8
[]

[Outputs]
  exodus = true
  csv = true
  [Console]
    type = Console
  []
[]

[Postprocessors]
  [temp_left]
    type = SideAverageValue
    boundary = 'left_right'
    variable = temp
  []

  [temp_right]
    type = SideAverageValue
    boundary = 'right_left'
    variable = temp
  []

  [flux_left]
    type = SideDiffusiveFluxIntegral
    variable = temp
    boundary = 'left_right'
    diffusivity = thermal_conductivity
  []
  [flux_right]
    type = SideDiffusiveFluxIntegral
    variable = temp
    boundary = 'right_left'
    diffusivity = thermal_conductivity
  []
  [ptot]
    type = ElementIntegralVariablePostprocessor
    variable = power_density
    block = 1
  []
  [convective_out]
    type = ConvectiveHeatTransferSideIntegral
    T_solid = temp
    boundary = 'right_right' # outer RVP
    T_fluid = ${outer_Tinf}
    htc = ${outer_htc}
  []
  [heat_balance] # should be equal to 0 upon convergence
    type = ParsedPostprocessor
    expression = '(convective_out - ptot) / ptot'
    pp_names = 'convective_out ptot'
  []
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = 'left_right right_left'
    variable = temp
  []
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/large_gap_heat_transfer_test_sphere_mortar.i)

sphere_outer_htc = 10 # W/m^2/K
sphere_outer_Tinf = 300 # K

[GlobalParams]
  order = SECOND
  family = LAGRANGE
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Mesh]
  [file]
    type = FileMeshGenerator
    file = cyl2D.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '2'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '3'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  allow_renumbering = false
  coord_type = RZ
[]

[Functions]
  [temp]
    type = PiecewiseLinear
    x = '0   1'
    y = '100 200'
  []
[]

[Variables]
  [temp]
    initial_condition = 500
  []
  [lm]
    order = SECOND
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[AuxVariables]
  [power_density]
    block = 'fuel'
    initial_condition = 50e3
  []
[]

[Kernels]
  [heat_conduction]
    type = HeatConduction
    variable = temp
    block = '1 2'
  []
  [heat_source]
    type = CoupledForce
    variable = temp
    block = 'fuel'
    v = power_density
  []
[]

[Materials]
  [heat1]
    type = HeatConductionMaterial
    block = '1 2'
    specific_heat = 1.0
    thermal_conductivity = 34.6
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    temperature = temp
    boundary = 2
    primary_emissivity = 0.0
    secondary_emissivity = 0.0
  []
  [conduction]
    type = GapFluxModelConduction
    temperature = temp
    boundary = 2
    gap_conductivity = 5.0
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    primary_boundary = 3
    primary_subdomain = 10000
    secondary_boundary = 2
    secondary_subdomain = 10001
    gap_flux_models = 'radiation conduction'
    gap_geometry_type = SPHERE
    sphere_origin = '0 0 0'
  []
[]

[BCs]
  [RPV_out_BC] # k \nabla T = h (T- T_inf) at RPV outer boundary
    type = ConvectiveFluxFunction # (Robin BC)
    variable = temp
    boundary = '4' # outer RPV
    coefficient = ${sphere_outer_htc}
    T_infinity = ${sphere_outer_Tinf}
  []
[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_factor_mat_solver_package'
  petsc_options_value = 'lu       superlu_dist'

  dt = 1
  dtmin = 0.01
  end_time = 1

  nl_rel_tol = 1e-12
  nl_abs_tol = 1e-7

[]

[Outputs]
  exodus = true
  csv = true
  [Console]
    type = Console
  []
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = '2 3'
    variable = temp
  []
[]

[Postprocessors]
  [temp_left]
    type = SideAverageValue
    boundary = 2
    variable = temp
  []

  [temp_right]
    type = SideAverageValue
    boundary = 3
    variable = temp
  []

  [flux_left]
    type = SideDiffusiveFluxIntegral
    variable = temp
    boundary = 2
    diffusivity = thermal_conductivity
  []

  [flux_right]
    type = SideDiffusiveFluxIntegral
    variable = temp
    boundary = 3
    diffusivity = thermal_conductivity
  []
  [ptot]
    type = ElementIntegralVariablePostprocessor
    variable = power_density
    block = 'fuel'
  []
  [sphere_convective_out]
    type = ConvectiveHeatTransferSideIntegral
    T_solid = temp
    boundary = '4' # outer RVP
    T_fluid = ${sphere_outer_Tinf}
    htc = ${sphere_outer_htc}
  []
  [heat_balance] # should be equal to 0 upon convergence
    type = ParsedPostprocessor
    expression = '(sphere_convective_out - ptot) / ptot'
    pp_names = 'sphere_convective_out ptot'
  []
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/modular_gap_heat_transfer_mortar_displaced_radiation.i)

[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [file]
    type = FileMeshGenerator
    file = 2blk-gap.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '101'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '100'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  allow_renumbering = false
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Variables]
  [temp]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_x]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [disp_y]
    order = FIRST
    family = LAGRANGE
    block = '1 2'
  []
  [lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[Materials]
  [left]
    type = ADHeatConductionMaterial
    block = 1
    thermal_conductivity = 0.01
    specific_heat = 1
  []

  [right]
    type = ADHeatConductionMaterial
    block = 2
    thermal_conductivity = 0.005
    specific_heat = 1
  []
[]

[Kernels]
  [hc_displaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = true
    block = '1'
  []
  [hc_undisplaced_block]
    type = ADHeatConduction
    variable = temp
    use_displaced_mesh = false
    block = '2'
  []
  [disp_x]
    type = Diffusion
    variable = disp_x
    block = '1 2'
  []
  [disp_y]
    type = Diffusion
    variable = disp_y
    block = '1 2'
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    temperature = temp
    boundary = 100
    primary_emissivity = 1.0
    secondary_emissivity = 1.0
    use_displaced_mesh = true
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    use_displaced_mesh = true
    primary_boundary = 100
    primary_subdomain = 10000
    secondary_boundary = 101
    secondary_subdomain = 10001
    gap_flux_models = radiation
  []
[]

[BCs]
  [left]
    type = DirichletBC
    variable = temp
    boundary = 'left'
    value = 100
  []

  [right]
    type = DirichletBC
    variable = temp
    boundary = 'right'
    value = 0
  []

  [left_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'left'
    value = .1
  []
  [right_disp_x]
    type = DirichletBC
    preset = false
    variable = disp_x
    boundary = 'right'
    value = 0
  []
  [bottom_disp_y]
    type = DirichletBC
    preset = false
    variable = disp_y
    boundary = 'bottom'
    value = 0
  []
[]

[Preconditioning]
  [fmp]
    type = SMP
    full = true
    solve_type = 'NEWTON'
  []
[]

[Executioner]
  type = Steady
  nl_rel_tol = 1e-11
  nl_abs_tol = 1.0e-10
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = '100 101'
    variable = 'temp'
  []
[]

[Outputs]
  exodus = false
  csv = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/gap_heat_transfer_sphere3D_mortar.i)

sphere_outer_htc = 10 # W/m^2/K
sphere_outer_Tinf = 300 # K

[GlobalParams]
  order = SECOND
  family = LAGRANGE
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Mesh]
  [file]
    type = FileMeshGenerator
    file = sphere3D.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '2'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '3'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
[]

[Functions]
  [temp]
    type = PiecewiseLinear
    x = '0   1'
    y = '100 200'
  []
[]

[Variables]
  [temp]
    initial_condition = 500
  []
  [lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[AuxVariables]
  # [gap_conductance]
  #   order = CONSTANT
  #   family = MONOMIAL
  # []
  [power_density]
    block = 'fuel'
    initial_condition = 50e3
  []
[]

[Kernels]
  [heat_conduction]
    type = HeatConduction
    variable = temp
    block = '1 2'
  []
  [heat_source]
    type = CoupledForce
    variable = temp
    block = 'fuel'
    v = power_density
  []
[]

# [AuxKernels]
#   [gap_cond]
#     type = MaterialRealAux
#     property = gap_conductance
#     variable = gap_conductance
#     boundary = 2
#   []
# []

[Materials]
  [heat1]
    type = HeatConductionMaterial
    block = '1 2'
    specific_heat = 1.0
    thermal_conductivity = 34.6
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    temperature = temp
    boundary = 2
    primary_emissivity = 0.0
    secondary_emissivity = 0.0
  []
  [conduction]
    type = GapFluxModelConduction
    temperature = temp
    boundary = 2
    gap_conductivity = 5.0
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    primary_boundary = 3
    primary_subdomain = 10000
    secondary_boundary = 2
    secondary_subdomain = 10001
    gap_flux_models = 'radiation conduction'
    gap_geometry_type = SPHERE
    sphere_origin = '0 0 0'
  []
[]

[BCs]
  [RPV_out_BC] # k \nabla T = h (T- T_inf) at RPV outer boundary
    type = ConvectiveFluxFunction # (Robin BC)
    variable = temp
    boundary = '4' # outer RPV
    coefficient = ${sphere_outer_htc}
    T_infinity = ${sphere_outer_Tinf}
  []
[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_factor_mat_solver_package'
  petsc_options_value = 'lu       superlu_dist'

  dt = 1
  dtmin = 0.01
  end_time = 1

  nl_rel_tol = 1e-12
  nl_abs_tol = 1e-7
[]

[Outputs]
  exodus = true
  csv = true
  [Console]
    type = Console
  []
[]

[Postprocessors]
  [temp_left]
    type = SideAverageValue
    boundary = 2
    variable = temp
  []

  [temp_right]
    type = SideAverageValue
    boundary = 3
    variable = temp
  []

  [flux_left]
    type = SideDiffusiveFluxIntegral
    variable = temp
    boundary = 2
    diffusivity = thermal_conductivity
  []
  [flux_right]
    type = SideDiffusiveFluxIntegral
    variable = temp
    boundary = 3
    diffusivity = thermal_conductivity
  []
  [ptot]
    type = ElementIntegralVariablePostprocessor
    variable = power_density
    block = 'fuel'
  []
  [sphere_convective_out]
    type = ConvectiveHeatTransferSideIntegral
    T_solid = temp
    boundary = '4' # outer RVP
    T_fluid = ${sphere_outer_Tinf}
    htc = ${sphere_outer_htc}
  []
  [heat_balance] # should be equal to 0 upon convergence
    type = ParsedPostprocessor
    expression = '(sphere_convective_out - ptot) / ptot'
    pp_names = 'sphere_convective_out ptot'
  []
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = '2 3'
    variable = temp
  []
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/large_gap_heat_transfer_test_sphere_mortar_error.i)

sphere_outer_htc = 10 # W/m^2/K
sphere_outer_Tinf = 300 # K

[GlobalParams]
  order = SECOND
  family = LAGRANGE
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Mesh]
  [file]
    type = FileMeshGenerator
    file = cyl2D.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '2'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '3'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  allow_renumbering = false
  coord_type = RZ
[]

[Functions]
  [temp]
    type = PiecewiseLinear
    x = '0   1'
    y = '100 200'
  []
[]

[Variables]
  [temp]
    initial_condition = 500
  []
  [lm]
    order = SECOND
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[AuxVariables]
  [power_density]
    block = 'fuel'
    initial_condition = 50e3
  []
[]

[Kernels]
  [heat_conduction]
    type = HeatConduction
    variable = temp
    block = '1 2'
  []
  [heat_source]
    type = CoupledForce
    variable = temp
    block = 'fuel'
    v = power_density
  []
[]

[Materials]
  [heat1]
    type = HeatConductionMaterial
    block = '1 2'
    specific_heat = 1.0
    thermal_conductivity = 34.6
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    temperature = temp
    boundary = 2
    primary_emissivity = 0.0
    secondary_emissivity = 0.0
  []
  [conduction]
    type = GapFluxModelConduction
    temperature = temp
    boundary = 2
    gap_conductivity = 5.0
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    primary_boundary = 3
    primary_subdomain = 10000
    secondary_boundary = 2
    secondary_subdomain = 10001
    gap_flux_models = 'radiation conduction'
    gap_geometry_type = SPHERE
  []
[]

[BCs]
  [RPV_out_BC] # k \nabla T = h (T- T_inf) at RPV outer boundary
    type = ConvectiveFluxFunction # (Robin BC)
    variable = temp
    boundary = '4' # outer RPV
    coefficient = ${sphere_outer_htc}
    T_infinity = ${sphere_outer_Tinf}
  []
[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_factor_mat_solver_package'
  petsc_options_value = 'lu       superlu_dist'

  dt = 1
  dtmin = 0.01
  end_time = 1

  nl_rel_tol = 1e-12
  nl_abs_tol = 1e-7

[]

[Outputs]
  exodus = true
  csv = true
  [Console]
    type = Console
  []
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = '2 3'
    variable = temp
  []
[]

[Postprocessors]
  [temp_left]
    type = SideAverageValue
    boundary = 2
    variable = temp
  []

  [temp_right]
    type = SideAverageValue
    boundary = 3
    variable = temp
  []

  [flux_left]
    type = SideDiffusiveFluxIntegral
    variable = temp
    boundary = 2
    diffusivity = thermal_conductivity
  []

  [flux_right]
    type = SideDiffusiveFluxIntegral
    variable = temp
    boundary = 3
    diffusivity = thermal_conductivity
  []
  [ptot]
    type = ElementIntegralVariablePostprocessor
    variable = power_density
    block = 'fuel'
  []
  [sphere_convective_out]
    type = ConvectiveHeatTransferSideIntegral
    T_solid = temp
    boundary = '4' # outer RVP
    T_fluid = ${sphere_outer_Tinf}
    htc = ${sphere_outer_htc}
  []
  [heat_balance] # should be equal to 0 upon convergence
    type = ParsedPostprocessor
    expression = '(sphere_convective_out - ptot) / ptot'
    pp_names = 'sphere_convective_out ptot'
  []
[]

(modules/combined/test/tests/3d-mortar-projection-tolerancing/test.i)

stress_free_temperature = 300
thermal_expansion_coeff = 6.66e-6

[Problem]
  type = FEProblem
[]

[GlobalParams]
  displacements = 'disp_x disp_y disp_z'
  temperature = T_K
[]

[Mesh]
  patch_update_strategy = iteration
  use_displaced_mesh = true
  patch_size = 40
  [ori]
    type = FileMeshGenerator
    file = 'test.msh'
  []
[]

[Variables]
  [disp_x]
    block = 'pellet_inner pellet_outer'
  []
  [disp_y]
    block = 'pellet_inner pellet_outer'
  []
  [disp_z]
    block = 'pellet_inner pellet_outer'
  []
  [T_K]
    [InitialCondition]
      type = ConstantIC
      value = 300.0
    []
  []
  [lm_pellet]
    block = 'pellet_secondary_subdomain'
  []
[]

[Kernels]
  [solid_x]
    type = ADStressDivergenceTensors
    variable = disp_x
    component = 0
    block = 'pellet_inner pellet_outer'
    use_displaced_mesh = false
  []
  [solid_y]
    type = ADStressDivergenceTensors
    variable = disp_y
    component = 1
    block = 'pellet_inner pellet_outer'
    use_displaced_mesh = false
  []
  [solid_z]
    type = ADStressDivergenceTensors
    variable = disp_z
    component = 2
    block = 'pellet_inner pellet_outer'
    use_displaced_mesh = false
  []
  [timeder]
    type = ADHeatConductionTimeDerivative
    variable = 'T_K'
    density_name = density
    specific_heat = specific_heat
    block = 'pellet_inner pellet_outer'
    use_displaced_mesh = true
  []
  [diff]
    type = ADHeatConduction
    variable = 'T_K'
    thermal_conductivity = thermal_conductivity
    block = 'pellet_inner pellet_outer'
    use_displaced_mesh = true
  []
  [heatsource]
    type = ADMatHeatSource
    variable = 'T_K'
    material_property = radial_source
    block = 'pellet_inner pellet_outer'
    use_displaced_mesh = true
  []
[]

[Debug]
  show_var_residual_norms = TRUE
[]

[BCs]
  [mirror_z]
    type = ADDirichletBC
    variable = disp_z
    boundary = 'mirror_innerp mirror_outerp'
    value = 0
  []
  [mirror_x]
    type = ADDirichletBC
    variable = disp_x
    boundary = 'mirror_innerp mirror_outerp'
    value = 0
  []
  [mirror_y]
    type = ADDirichletBC
    variable = disp_y
    boundary = 'mirror_innerp mirror_outerp'
    value = 0
  []
[]

[Materials]
  [pellet_properties]
    type = ADGenericConstantMaterial
    prop_names = 'density  thermal_conductivity specific_heat'
    prop_values = '3.3112e3  34 1.2217e3'
    block = 'pellet_inner pellet_outer'
  []
  [pulse_shape_linear]
    type = ADGenericFunctionMaterial
    prop_values = '5e10*max(11455*(t)/7,1e-9)'
    prop_names = 'radial_source'
    block = 'pellet_inner pellet_outer'
    use_displaced_mesh = false
  []
  [strain]
    type = ADComputeSmallStrain
    displacements = 'disp_x disp_y disp_z'
    eigenstrain_names = eigenstrain #nameS!
    block = 'pellet_inner pellet_outer'
  []
  [thermal_strain]
    type = ADComputeThermalExpansionEigenstrain
    stress_free_temperature = ${stress_free_temperature}
    thermal_expansion_coeff = ${thermal_expansion_coeff}
    eigenstrain_name = eigenstrain
    block = 'pellet_inner pellet_outer'
  []
  [elasticity]
    type = ADComputeIsotropicElasticityTensor
    youngs_modulus = 3.306e11
    poissons_ratio = 0.329
  []
  [stress]
    type = ADComputeLinearElasticStress
    block = 'pellet_inner pellet_outer'
  []
[]

[Contact]
  [pellet]
    primary = void_pellet_0
    secondary = void_pellet_1
    model = frictionless
    formulation = mortar
    c_normal = 1e6
    correct_edge_dropping = true
  []
[]

[UserObjects]
  [conduction]
    type = GapFluxModelConduction
    temperature = T_K
    boundary = 'void_pellet_0 void_pellet_1'
    gap_conductivity = 0.4
    use_displaced_mesh = true
  []
  [rad_pellet]
    type = GapFluxModelRadiation
    temperature = T_K
    boundary = void_pellet_0
    primary_emissivity = 0.37
    secondary_emissivity = 0.37
    use_displaced_mesh = true
  []
[]

[Constraints]
  [gap_pellet]
    type = ModularGapConductanceConstraint
    variable = lm_pellet
    secondary_variable = T_K
    primary_boundary = 'void_pellet_0'
    primary_subdomain = pellet_primary_subdomain
    secondary_boundary = 'void_pellet_1'
    secondary_subdomain = pellet_secondary_subdomain
    gap_flux_models = 'conduction rad_pellet' #closed_pellet
    gap_geometry_type = 'CYLINDER'
    cylinder_axis_point_1 = '0 0 0'
    cylinder_axis_point_2 = '0 0 1'
    use_displaced_mesh = true
    quadrature = SECOND
  []
[]

[Executioner]
  type = Transient
  solve_type = NEWTON
  petsc_options_iname = '-pc_type -pc_factor_mat_solver_package -pc_factor_shift_type'
  petsc_options_value = 'lu       superlu_dist                  NONZERO'
  automatic_scaling = true
  line_search = none
  ignore_variables_for_autoscaling = 'pellet_normal_lm'
  compute_scaling_once = true
  scaling_group_variables = 'disp_x disp_y disp_z; T_K'
  nl_rel_tol = 1e-50
  nl_abs_tol = 1e-8
  nl_max_its = 20
  dtmin = 1e-3
  dt = 1e-3
  start_time = 0e-3
  end_time = 1
[]

[Outputs]
  [exodus]
    type = Exodus
    file_base = constMat
  []
  print_linear_residuals = false
[]

(modules/combined/test/tests/gap_heat_transfer_mortar/finite-2d/closed_gap_thermomechanical_mortar_contact.i)

## Units in the input file: m-Pa-s-K

[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 40
    ny = 10
    xmax = 1
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 40
    ny = 10
    xmin = 1
    xmax = 2
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
  patch_update_strategy = iteration
[]

[Variables]
  [disp_x]
    block = 'left_block right_block'
  []
  [disp_y]
    block = 'left_block right_block'
  []
  [temperature]
    initial_condition = 300.0
  []
  [temperature_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[Physics]
  [SolidMechanics/QuasiStatic]
    [steel]
      strain = FINITE
      add_variables = false
      use_automatic_differentiation = true
      generate_output = 'strain_xx strain_xy strain_yy stress_xx stress_xy stress_yy'
      additional_generate_output = 'vonmises_stress'
      additional_material_output_family = 'MONOMIAL'
      additional_material_output_order = 'FIRST'
      eigenstrain_names = steel_thermal_expansion
      block = 'left_block'
    []
    [aluminum]
      strain = FINITE
      add_variables = false
      use_automatic_differentiation = true
      generate_output = 'strain_xx strain_xy strain_yy stress_xx stress_xy stress_yy'
      additional_generate_output = 'vonmises_stress'
      additional_material_output_family = 'MONOMIAL'
      additional_material_output_order = 'FIRST'
      eigenstrain_names = aluminum_thermal_expansion
      block = 'right_block'
    []
  []
[]

[Kernels]
  [HeatDiff_steel]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = steel_thermal_conductivity
    block = 'left_block'
  []
  [HeatTdot_steel]
    type = ADHeatConductionTimeDerivative
    variable = temperature
    specific_heat = steel_heat_capacity
    density_name = steel_density
    block = 'left_block'
  []
  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    block = 'right_block'
  []
  [HeatTdot_aluminum]
    type = ADHeatConductionTimeDerivative
    variable = temperature
    specific_heat = aluminum_heat_capacity
    density_name = aluminum_density
    block = 'right_block'
  []
[]

[BCs]
  [fixed_bottom_edge]
    type = ADDirichletBC
    variable = disp_y
    value = 0
    boundary = 'moving_block_bottom fixed_block_bottom'
  []
  [fixed_outer_edge]
    type = ADDirichletBC
    variable = disp_x
    value = 0
    boundary = 'fixed_block_right'
  []
  [displacement_left_block]
    type = ADFunctionDirichletBC
    variable = disp_x
    function = '2.0e-7*t'
    boundary = 'moving_block_left'
  []
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 800
    boundary = 'fixed_block_right'
  []
[]

[Contact]
  [interface]
    primary = moving_block_right
    secondary = fixed_block_left
    model = frictionless
    formulation = mortar
    correct_edge_dropping = true
  []
[]

[Constraints]
  [thermal_contact]
    type = ModularGapConductanceConstraint
    variable = temperature_interface_lm
    secondary_variable = temperature
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed'
    use_displaced_mesh = true
  []
[]

[Materials]
  [steel_elasticity_tensor]
    type = ADComputeIsotropicElasticityTensor
    youngs_modulus = 1.93e11 #in Pa, 193 GPa, stainless steel 304
    poissons_ratio = 0.29
    block = 'left_block'
  []
  [steel_stress]
    type = ADComputeFiniteStrainElasticStress
    block = 'left_block'
  []
  [steel_thermal_expansion]
    type = ADComputeThermalExpansionEigenstrain
    thermal_expansion_coeff = 17.3e-6 # stainless steel 304
    stress_free_temperature = 300.0
    temperature = temperature
    eigenstrain_name = 'steel_thermal_expansion'
    block = 'left_block'
  []
  [steel_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'steel_density steel_thermal_conductivity steel_heat_capacity steel_hardness'
    prop_values = ' 8e3            16.2                     0.5                 129' ## for stainless steel 304
    block = 'left_block'
  []

  [aluminum_elasticity_tensor]
    type = ADComputeIsotropicElasticityTensor
    youngs_modulus = 6.8e10 #in Pa, 68 GPa, aluminum
    poissons_ratio = 0.36
    block = 'right_block'
  []
  [aluminum_stress]
    type = ADComputeFiniteStrainElasticStress
    block = 'right_block'
  []
  [aluminum_thermal_expansion]
    type = ADComputeThermalExpansionEigenstrain
    thermal_expansion_coeff = 24.0e-6 # aluminum
    stress_free_temperature = 300.0
    temperature = temperature
    eigenstrain_name = 'aluminum_thermal_expansion'
    block = 'right_block'
  []
  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density aluminum_thermal_conductivity aluminum_heat_capacity aluminum_hardness'
    prop_values = ' 2.7e3            210                           0.9                   15' #for 99% pure Al
    block = 'right_block'
  []
[]

[UserObjects]
  [closed]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = steel_thermal_conductivity
    secondary_conductivity = aluminum_thermal_conductivity
    temperature = temperature
    contact_pressure = interface_normal_lm
    primary_hardness = steel_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
[]

[Postprocessors]
  [steel_pt_interface_temperature]
    type = NodalVariableValue
    nodeid = 245
    variable = temperature
  []
  [aluminum_pt_interface_temperature]
    type = NodalVariableValue
    nodeid = 657
    variable = temperature
  []
  [steel_element_interface_stress]
    type = ElementalVariableValue
    variable = vonmises_stress
    elementid = 199
  []
  [aluminum_element_interface_stress]
    type = ElementalVariableValue
    variable = vonmises_stress
    elementid = 560
  []
  [interface_heat_flux_steel]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = moving_block_right
    diffusivity = steel_thermal_conductivity
  []
  [interface_heat_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = fixed_block_left
    diffusivity = aluminum_thermal_conductivity
  []
[]


[Executioner]
  type = Transient
  solve_type = NEWTON
  automatic_scaling = false
  line_search = 'none'

  # mortar contact solver options
  petsc_options = '-snes_converged_reason -pc_svd_monitor'
  petsc_options_iname = '-pc_type -pc_factor_mat_solver_type'
  petsc_options_value = ' lu       superlu_dist'
  snesmf_reuse_base = false

  nl_rel_tol = 1e-8
  nl_max_its = 20
  l_max_its = 50

  dt = 2
  end_time = 10
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/combined/test/tests/gap_heat_transfer_mortar/finite-2d/varied_pressure_thermomechanical_mortar.i)

## Units in the input file: m-Pa-s-K

[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 20
    ny = 10
    xmax = 0.25
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 20
    ny = 13
    xmin = 0.25
    xmax = 0.5
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
  patch_update_strategy = iteration
[]

[Variables]
  [disp_x]
    block = 'left_block right_block'
  []
  [disp_y]
    block = 'left_block right_block'
  []
  [temperature]
    initial_condition = 300.0
  []
  [temperature_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[Physics]
  [SolidMechanics/QuasiStatic]
    [steel]
      strain = FINITE
      add_variables = false
      use_automatic_differentiation = true
      generate_output = 'strain_xx strain_xy strain_yy stress_xx stress_xy stress_yy'
      additional_generate_output = 'vonmises_stress'
      additional_material_output_family = 'MONOMIAL'
      additional_material_output_order = 'FIRST'
      block = 'left_block'
    []
    [aluminum]
      strain = FINITE
      add_variables = false
      use_automatic_differentiation = true
      generate_output = 'strain_xx strain_xy strain_yy stress_xx stress_xy stress_yy'
      additional_generate_output = 'vonmises_stress'
      additional_material_output_family = 'MONOMIAL'
      additional_material_output_order = 'FIRST'
      block = 'right_block'
    []
  []
[]

[Kernels]
  [HeatDiff_steel]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = steel_thermal_conductivity
    block = 'left_block'
  []
  [HeatTdot_steel]
    type = ADHeatConductionTimeDerivative
    variable = temperature
    specific_heat = steel_heat_capacity
    density_name = steel_density
    block = 'left_block'
  []
  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    block = 'right_block'
  []
  [HeatTdot_aluminum]
    type = ADHeatConductionTimeDerivative
    variable = temperature
    specific_heat = aluminum_heat_capacity
    density_name = aluminum_density
    block = 'right_block'
  []
[]

[BCs]
  [fixed_bottom_edge]
    type = ADDirichletBC
    variable = disp_y
    value = 0
    boundary = 'moving_block_bottom fixed_block_bottom'
  []
  [fixed_outer_edge]
    type = ADDirichletBC
    variable = disp_x
    value = 0
    boundary = 'fixed_block_right'
  []
  [pressure_left_block]
    type = ADPressure
    variable = disp_x
    boundary = 'moving_block_left'
    function = '1e4*t*y'
  []
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 800
    boundary = 'fixed_block_right'
  []
[]

[Contact]
  [interface]
    primary = moving_block_right
    secondary = fixed_block_left
    model = frictionless
    formulation = mortar
    correct_edge_dropping = true
  []
[]

[Constraints]
  [thermal_contact]
    type = ModularGapConductanceConstraint
    variable = temperature_interface_lm
    secondary_variable = temperature
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed'
    use_displaced_mesh = true
  []
[]

[Materials]
  [steel_elasticity_tensor]
    type = ADComputeIsotropicElasticityTensor
    youngs_modulus = 1.93e11 #in Pa, 193 GPa, stainless steel 304
    poissons_ratio = 0.29
    block = 'left_block'
  []
  [steel_stress]
    type = ADComputeFiniteStrainElasticStress
    block = 'left_block'
  []
  [steel_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'steel_density steel_thermal_conductivity steel_heat_capacity steel_hardness'
    prop_values = ' 8e3            16.2                     0.5                 129' ## for stainless steel 304
    block = 'left_block'
  []

  [aluminum_elasticity_tensor]
    type = ADComputeIsotropicElasticityTensor
    youngs_modulus = 6.8e10 #in Pa, 68 GPa, aluminum
    poissons_ratio = 0.36
    block = 'right_block'
  []
  [aluminum_stress]
    type = ADComputeFiniteStrainElasticStress
    block = 'right_block'
  []
  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density aluminum_thermal_conductivity aluminum_heat_capacity aluminum_hardness'
    prop_values = ' 2.7e3            210                           0.9                   15' #for 99% pure Al
    block = 'right_block'
  []
[]

[UserObjects]
  [closed]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = steel_thermal_conductivity
    secondary_conductivity = aluminum_thermal_conductivity
    temperature = temperature
    contact_pressure = interface_normal_lm
    primary_hardness = steel_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
[]

[Postprocessors]
  [contact_pressure_max]
    type = NodalExtremeValue
    variable = interface_normal_lm
    block = interface_secondary_subdomain
    value_type = max
  []
  [contact_pressure_average]
    type = AverageNodalVariableValue
    variable = interface_normal_lm
    block = interface_secondary_subdomain
  []
  [contact_pressure_min]
    type = NodalExtremeValue
    variable = interface_normal_lm
    block = interface_secondary_subdomain
    value_type = min
  []
  [interface_temperature_max]
    type = NodalExtremeValue
    variable = temperature
    block = interface_secondary_subdomain
    value_type = max
  []
  [interface_temperature_average]
    type = AverageNodalVariableValue
    variable = temperature
    block = interface_secondary_subdomain
  []
  [interface_temperature_min]
    type = NodalExtremeValue
    variable = temperature
    block = interface_secondary_subdomain
    value_type = min
  []
[]


[Executioner]
  type = Transient
  solve_type = NEWTON
  automatic_scaling = false
  line_search = 'none'

  # mortar contact solver options
  petsc_options = '-snes_converged_reason -pc_svd_monitor'
  petsc_options_iname = '-pc_type -pc_factor_mat_solver_type'
  petsc_options_value = ' lu       superlu_dist'
  snesmf_reuse_base = false

  nl_rel_tol = 1e-7
  nl_max_its = 20
  l_max_its = 50

  dt = 0.125
  end_time = 1
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/fv_modular_gap_heat_transfer_mortar_radiation_conduction.i)

[Mesh]
  inactive = 'translate'
  [file]
    type = FileMeshGenerator
    file = 2blk-gap.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '101'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '100'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  [translate]
    type = TransformGenerator
    transform = translate
    input = primary
    vector_value = '1 0 0'
  []
[]

[Problem]
  kernel_coverage_check = false
  material_coverage_check = false
[]

[Variables]
  [temp]
    type = MooseVariableFVReal
    block = '1 2'
  []
  [lm]
    order = CONSTANT
    family = MONOMIAL
    block = 'secondary_lower'
  []
[]

[Materials]
  [left]
    type = ADGenericFunctorMaterial
    block = 1
    prop_names = 'thermal_conductivity'
    prop_values = '0.01'
  []

  [right]
    type = ADGenericFunctorMaterial
    block = 2
    prop_names = 'thermal_conductivity'
    prop_values = '0.005'
  []
[]

[FVKernels]
  [hc]
    type = FVDiffusion
    variable = temp
    block = '1 2'
    coeff = 'thermal_conductivity'
  []
[]

[UserObjects]
  [radiation]
    type = FunctorGapFluxModelRadiation
    temperature = temp
    boundary = 100
    primary_emissivity = 1.0
    secondary_emissivity = 1.0
  []
  [conduction]
    type = FunctorGapFluxModelConduction
    temperature = temp
    boundary = 100
    gap_conductivity = 0.02
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    primary_boundary = 100
    primary_subdomain = 10000
    secondary_boundary = 101
    secondary_subdomain = 10001
    gap_flux_models = 'radiation conduction'
    ghost_higher_d_neighbors = true
  []
[]

[FVBCs]
  [left]
    type = FVDirichletBC
    variable = temp
    boundary = 'left'
    value = 100
  []

  [right]
    type = FVDirichletBC
    variable = temp
    boundary = 'right'
    value = 0
  []
[]

[Executioner]
  type = Steady
  nl_rel_tol = 1e-11
  nl_abs_tol = 1.0e-10
  solve_type = NEWTON
[]

[Outputs]
  exodus = true
[]

(modules/heat_transfer/test/tests/interface_heating_mortar/constraint_joule_heating_single_material.i)

## Units in the input file: m-Pa-s-K-V

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 10
    xmax = 0.1
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 10
    xmin = 0.1
    xmax = 0.2
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
  [interface_secondary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'fixed_block_left'
    new_block_id = 3
    new_block_name = 'interface_secondary_subdomain'
    input = block_rename
  []
  [interface_primary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'moving_block_right'
    new_block_id = 4
    new_block_name = 'interface_primary_subdomain'
    input = interface_secondary_subdomain
  []
[]

[Problem]
  type = ReferenceResidualProblem
  reference_vector = 'ref'
  extra_tag_vectors = 'ref'
[]

[Variables]
  [temperature]
    initial_condition = 300.0
  []
  [potential]
  []
  [potential_interface_lm]
    block = 'interface_secondary_subdomain'
  []
  [temperature_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[AuxVariables]
  [interface_normal_lm]
    order = FIRST
    family = LAGRANGE
    block = 'interface_secondary_subdomain'
    initial_condition = 1.0
  []
[]

[Kernels]
  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block right_block'
  []
  [electric_aluminum]
    type = ADMatDiffusion
    variable = potential
    diffusivity = aluminum_electrical_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block right_block'
  []
[]

[BCs]
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'fixed_block_right'
  []

  [electric_left]
    type = ADDirichletBC
    variable = potential
    value = 0.0
    boundary = moving_block_left
  []
  [electric_right]
    type = ADDirichletBC
    variable = potential
    value = 3.0e-1
    boundary = fixed_block_right
  []
[]

[Constraints]
  [thermal_contact]
    type = ModularGapConductanceConstraint
    variable = temperature_interface_lm
    secondary_variable = temperature
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed_temperature'
  []
  [electrical_contact]
    type = ModularGapConductanceConstraint
    variable = potential_interface_lm
    secondary_variable = potential
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed_electric'
  []
  [interface_heating]
    type = ADInterfaceJouleHeatingConstraint
    potential_lagrange_multiplier = potential_interface_lm
    secondary_variable = temperature
    primary_electrical_conductivity = aluminum_electrical_conductivity
    secondary_electrical_conductivity = aluminum_electrical_conductivity
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
  []
[]

[Materials]
  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density aluminum_thermal_conductivity aluminum_heat_capacity aluminum_electrical_conductivity aluminum_hardness'
    prop_values = ' 2.7e3           210                           900.0                   3.7e7                           1.0' #for 99% pure Al
    block = 'left_block right_block interface_secondary_subdomain'
  []
[]

[UserObjects]
  [closed_temperature]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = aluminum_thermal_conductivity
    secondary_conductivity = aluminum_thermal_conductivity
    temperature = temperature
    contact_pressure = interface_normal_lm
    primary_hardness = aluminum_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
  [closed_electric]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = aluminum_electrical_conductivity
    secondary_conductivity = aluminum_electrical_conductivity
    temperature = potential
    contact_pressure = interface_normal_lm
    primary_hardness = aluminum_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
[]

[Postprocessors]
  [aluminum_interface_temperature]
    type = AverageNodalVariableValue
    variable = temperature
    block = interface_secondary_subdomain
  []
  [interface_heat_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = fixed_block_left
    diffusivity = aluminum_thermal_conductivity
  []
  [aluminum_interface_potential]
    type = AverageNodalVariableValue
    variable = potential
    block = interface_secondary_subdomain
  []
  [interface_electrical_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = potential
    boundary = fixed_block_left
    diffusivity = aluminum_electrical_conductivity
  []
[]

[Executioner]
  type = Steady
  solve_type = NEWTON
  automatic_scaling = false
  line_search = 'none'

  nl_abs_tol = 1e-10
  nl_rel_tol = 1e-6
  nl_max_its = 50
  nl_forced_its = 1
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/combined/test/tests/gap_heat_transfer_mortar/small-2d/open_gap_pressure_dependent.i)

## Units in the input file: m-Pa-s-K

[GlobalParams]
  displacements = 'disp_x disp_y'
[]

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 40
    ny = 10
    xmax = 1
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 40
    ny = 10
    xmin = 1.0001
    xmax = 2.0001
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
[]

[Variables]
  [disp_x]
    block = 'left_block right_block'
  []
  [disp_y]
    block = 'left_block right_block'
  []
  [temperature]
    initial_condition = 525.0
  []
  [temperature_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[Physics]
  [SolidMechanics/QuasiStatic]
    [steel]
      strain = SMALL
      add_variables = false
      use_automatic_differentiation = true
      additional_generate_output = 'vonmises_stress'
      additional_material_output_family = 'MONOMIAL'
      additional_material_output_order = 'FIRST'
      block = 'left_block'
    []
    [aluminum]
      strain = SMALL
      add_variables = false
      use_automatic_differentiation = true
      additional_generate_output = 'vonmises_stress'
      additional_material_output_family = 'MONOMIAL'
      additional_material_output_order = 'FIRST'
      block = 'right_block'
    []
  []
[]

[Kernels]
  [HeatDiff_steel]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = steel_thermal_conductivity
    block = 'left_block'
  []
  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    block = 'right_block'
  []
[]

[BCs]
  [fixed_bottom_edge]
    type = ADDirichletBC
    variable = disp_y
    value = 0
    boundary = 'moving_block_bottom fixed_block_bottom'
  []
  [fixed_outer_edge]
    type = ADDirichletBC
    variable = disp_x
    value = 0
    boundary = 'fixed_block_right'
  []
  [pressure_left_block]
    type = ADPressure
    variable = disp_x
    boundary = 'moving_block_left'
    component = 0
    function = 1*t
  []
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 800
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 250
    boundary = 'fixed_block_right'
  []
[]

[Contact]
  [interface]
    primary = moving_block_right
    secondary = fixed_block_left
    model = frictionless
    formulation = mortar
    correct_edge_dropping = true
  []
[]

[Constraints]
  [thermal_contact]
    type = ModularGapConductanceConstraint
    variable = temperature_interface_lm
    secondary_variable = temperature
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed'
    use_displaced_mesh = true
  []
[]

[Materials]
  [steel_elasticity_tensor]
    type = ADComputeIsotropicElasticityTensor
    youngs_modulus = 1.93e11 #in Pa, 193 GPa, stainless steel 304
    poissons_ratio = 0.29
    block = 'left_block'
  []
  [steel_stress]
    type = ADComputeLinearElasticStress
    block = 'left_block'
  []
  [steel_density]
    type = ADGenericConstantMaterial
    prop_names = 'steel_density'
    prop_values = 8e3 #in kg/m^3, stainless steel 304
    block = 'left_block'
  []
  [steel_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'steel_thermal_conductivity steel_heat_capacity steel_emissivity'
    prop_values = '16.2 0.5 0.6' ## for stainless steel 304
    block = 'left_block'
  []

  [aluminum_elasticity_tensor]
    type = ADComputeIsotropicElasticityTensor
    youngs_modulus = 6.8e10 #in Pa, 68 GPa, aluminum
    poissons_ratio = 0.36
    block = 'right_block'
  []
  [aluminum_stress]
    type = ADComputeLinearElasticStress
    block = 'right_block'
  []
  [aluminum_density]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density'
    prop_values = 2.7e3 #in kg/m^3, stainless steel 304
    block = 'right_block'
  []
  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_thermal_conductivity aluminum_heat_capacity aluminum_emissivity'
    prop_values = '210 0.9 0.25'
    block = 'right_block'
  []
[]

[UserObjects]
  [closed]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = steel_thermal_conductivity
    secondary_conductivity = aluminum_thermal_conductivity
    temperature = temperature
    primary_hardness = 1.0
    secondary_hardness = 1.0
    boundary = moving_block_right
    contact_pressure = interface_normal_lm
  []
[]

[Postprocessors]
  [steel_pt_interface_temperature]
    type = NodalVariableValue
    nodeid = 245
    variable = temperature
  []
  [aluminum_pt_interface_temperature]
    type = NodalVariableValue
    nodeid = 657
    variable = temperature
  []
  [interface_heat_flux_steel]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = moving_block_right
    diffusivity = steel_thermal_conductivity
  []
  [interface_heat_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = fixed_block_left
    diffusivity = aluminum_thermal_conductivity
  []
  [steel_element_interface_stress]
    type = ElementalVariableValue
    variable = vonmises_stress
    elementid = 199
  []
  [aluminum_element_interface_stress]
    type = ElementalVariableValue
    variable = vonmises_stress
    elementid = 560
  []
[]


[Executioner]
  type = Steady
  solve_type = NEWTON
  automatic_scaling = false
  line_search = 'none'

  petsc_options_iname = '-pc_type'
  petsc_options_value = 'lu'
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/heat_transfer/test/tests/interface_heating_mortar/constraint_joule_heating_single_material_insulated.i)

## Units in the input file: m-Pa-s-K-V

# In this steady-state, symmetric simulation, the temperature at the interface between
# the two blocks of aluminum can be calculated through Fourier's law (see the documentation
# page for ADInterfaceJouleHeatingConstraint for the relevant formulas).
#
# With the prescribed 0.0 V (left) and 0.3V (right) potential boundary conditions, the
# electric potential drop is 9.25e6 [V * S / m^2]. From this current-density-like LM variable,
# the volumetric heat source at the interface is calculated as
#   q = 1.15625e6 [W/m^3}
# Because of the 2D nature of this problem, the volumetric heat source is equal to
# the negative of the heat flux at the interface.
#
# Finally, the temperature at the interface is computed as a function of the block width,
# thermal conductivity, and specified temperature boundary condition (300K on both the
# left and right edges):
#   T_{interface} = 850.5952K
# which matches the simulation result to the 6 decimal places shown.

[Mesh]
  [left_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 10
    xmax = 0.1
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = moving_block
  []
  [left_block]
    type = SubdomainIDGenerator
    input = left_rectangle
    subdomain_id = 1
  []
  [right_rectangle]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 100
    ny = 10
    xmin = 0.1
    xmax = 0.2
    ymin = 0
    ymax = 0.5
    boundary_name_prefix = fixed_block
    boundary_id_offset = 4
  []
  [right_block]
    type = SubdomainIDGenerator
    input = right_rectangle
    subdomain_id = 2
  []
  [two_blocks]
    type = MeshCollectionGenerator
    inputs = 'left_block right_block'
  []
  [block_rename]
    type = RenameBlockGenerator
    input = two_blocks
    old_block = '1 2'
    new_block = 'left_block right_block'
  []
  [interface_secondary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'fixed_block_left'
    new_block_id = 3
    new_block_name = 'interface_secondary_subdomain'
    input = block_rename
  []
  [interface_primary_subdomain]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'moving_block_right'
    new_block_id = 4
    new_block_name = 'interface_primary_subdomain'
    input = interface_secondary_subdomain
  []
[]

[Problem]
  type = ReferenceResidualProblem
  reference_vector = 'ref'
  extra_tag_vectors = 'ref'
[]

[Variables]
  [temperature]
    initial_condition = 300.0
  []
  [potential]
  []
  [potential_interface_lm]
    block = 'interface_secondary_subdomain'
  []
[]

[AuxVariables]
  [interface_normal_lm]
    order = FIRST
    family = LAGRANGE
    block = 'interface_secondary_subdomain'
    initial_condition = 1.0
  []
[]

[Kernels]
  [HeatDiff_aluminum]
    type = ADHeatConduction
    variable = temperature
    thermal_conductivity = aluminum_thermal_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block right_block'
  []
  [electric_aluminum]
    type = ADMatDiffusion
    variable = potential
    diffusivity = aluminum_electrical_conductivity
    extra_vector_tags = 'ref'
    block = 'left_block right_block'
  []
[]

[BCs]
  [temperature_left]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'moving_block_left'
  []
  [temperature_right]
    type = ADDirichletBC
    variable = temperature
    value = 300
    boundary = 'fixed_block_right'
  []

  [electric_left]
    type = ADDirichletBC
    variable = potential
    value = 0.0
    boundary = moving_block_left
  []
  [electric_right]
    type = ADDirichletBC
    variable = potential
    value = 3.0e-1
    boundary = fixed_block_right
  []
[]

[Constraints]
  [electrical_contact]
    type = ModularGapConductanceConstraint
    variable = potential_interface_lm
    secondary_variable = potential
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
    gap_flux_models = 'closed_electric'
  []
  [interface_heating]
    type = ADInterfaceJouleHeatingConstraint
    potential_lagrange_multiplier = potential_interface_lm
    secondary_variable = temperature
    primary_electrical_conductivity = aluminum_electrical_conductivity
    secondary_electrical_conductivity = aluminum_electrical_conductivity
    primary_boundary = moving_block_right
    primary_subdomain = interface_primary_subdomain
    secondary_boundary = fixed_block_left
    secondary_subdomain = interface_secondary_subdomain
  []
[]

[Materials]
  [aluminum_thermal_properties]
    type = ADGenericConstantMaterial
    prop_names = 'aluminum_density aluminum_thermal_conductivity aluminum_heat_capacity aluminum_electrical_conductivity aluminum_hardness'
    prop_values = ' 2.7e3           210                           900.0                   3.7e7                           1.0' #for 99% pure Al
    block = 'left_block right_block interface_secondary_subdomain'
  []
[]

[UserObjects]
  [closed_electric]
    type = GapFluxModelPressureDependentConduction
    primary_conductivity = aluminum_electrical_conductivity
    secondary_conductivity = aluminum_electrical_conductivity
    temperature = potential
    contact_pressure = interface_normal_lm
    primary_hardness = aluminum_hardness
    secondary_hardness = aluminum_hardness
    boundary = moving_block_right
  []
[]

[Postprocessors]
  [aluminum_interface_temperature]
    type = AverageNodalVariableValue
    variable = temperature
    block = interface_secondary_subdomain
  []
  [interface_heat_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = temperature
    boundary = fixed_block_left
    diffusivity = aluminum_thermal_conductivity
  []
  [aluminum_interface_potential]
    type = AverageNodalVariableValue
    variable = potential
    block = interface_secondary_subdomain
  []
  [interface_electrical_flux_aluminum]
    type = ADSideDiffusiveFluxAverage
    variable = potential
    boundary = fixed_block_left
    diffusivity = aluminum_electrical_conductivity
  []
[]

[Executioner]
  type = Steady
  solve_type = NEWTON
  automatic_scaling = false
  line_search = 'none'

  nl_abs_tol = 2e-10
  nl_rel_tol = 1e-6
  nl_max_its = 50
  nl_forced_its = 1
[]

[Outputs]
  csv = true
  perf_graph = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/gap_heat_transfer_radiation_test.i)

#
# This test replicates the legacy heat transfter test
# gap_heat_transfer_radiation/gap_heat_transfer_radiation_test.i
# The flux post processors give 3.753945e+01
#

[Mesh]
  [file]
    type = FileMeshGenerator
    file = gap_heat_transfer_radiation_test.e
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '2'
    new_block_id = '200'
    new_block_name = 'secondary_lower'
    input = file
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = '3'
    new_block_id = '300'
    new_block_name = 'primary_lower'
    input = secondary
  []
[]

[Functions]
  [temp]
    type = PiecewiseLinear
    x = '0   1'
    y = '200 200'
  []
[]

[Variables]
  [temp]
    order = FIRST
    family = LAGRANGE
    initial_condition = 100
    scaling = 1e-8
  []
  [lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
    scaling = 1e-1
  []
[]

[Kernels]
  [heat]
    type = HeatConduction
    variable = temp
    block = '1 2'
  []
[]

[BCs]
  [temp_far_left]
    type = FunctionDirichletBC
    boundary = 1
    variable = temp
    function = temp
  []

  [temp_far_right]
    type = DirichletBC
    boundary = 4
    variable = temp
    value = 100
  []
[]

[UserObjects]
  [radiative]
    type = GapFluxModelRadiative
    secondary_emissivity = 0.5
    primary_emissivity = 0.5
    temperature = temp
    boundary = 3
  []
  [simple]
    type = GapFluxModelSimple
    k = 0.09187557
    temperature = temp
    boundary = 3
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = temp
    primary_boundary = 3
    primary_subdomain = 300
    secondary_boundary = 2
    secondary_subdomain = 200
    gap_flux_models = 'simple radiative'
  []
[]

[Materials]
  [heat1]
    type = HeatConductionMaterial
    block = '1 2'
    specific_heat = 1.0
    thermal_conductivity = 10000000.0
  []
  [density]
    type = GenericConstantMaterial
    block = '1 2'
    prop_names = 'density'
    prop_values = '1.0'
  []
[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'
  end_time = 1.0
[]

[Postprocessors]
  [temp_left]
    type = SideAverageValue
    boundary = 2
    variable = temp
    execute_on = 'initial timestep_end'
  []

  [temp_right]
    type = SideAverageValue
    boundary = 3
    variable = temp
    execute_on = 'initial timestep_end'
  []

  [flux_left]
    type = SideDiffusiveFluxIntegral
    variable = temp
    boundary = 2
    diffusivity = thermal_conductivity
  []

  [flux_right]
    type = SideDiffusiveFluxIntegral
    variable = temp
    boundary = 3
    diffusivity = thermal_conductivity
  []
[]

[Outputs]
  exodus = true
[]

(modules/heat_transfer/test/tests/gap_heat_transfer_mortar/large_gap_heat_transfer_test_cylinder_mortar.i)

rpv_core_gap_size = 0.15

core_outer_radius = 2
rpv_inner_radius = '${fparse 2 + rpv_core_gap_size}'
rpv_outer_radius = '${fparse 2.5 + rpv_core_gap_size}'

rpv_outer_htc = 10 # W/m^2/K
rpv_outer_Tinf = 300 # K

core_blocks = '1'
rpv_blocks = '3'

[Mesh]
  [core_gap_rpv]
    type = ConcentricCircleMeshGenerator
    num_sectors = 10
    radii = '${core_outer_radius} ${rpv_inner_radius} ${rpv_outer_radius}'
    rings = '2 1 2'
    has_outer_square = false
    preserve_volumes = true
    portion = full
  []
  [rename_core_bdy]
    type = SideSetsBetweenSubdomainsGenerator
    input = core_gap_rpv
    primary_block = 1
    paired_block = 2
    new_boundary = 'core_outer'
  []
  [rename_inner_rpv_bdy]
    type = SideSetsBetweenSubdomainsGenerator
    input = rename_core_bdy
    primary_block = 3
    paired_block = 2
    new_boundary = 'rpv_inner'
  []
  [2d_mesh]
    type = BlockDeletionGenerator
    input = rename_inner_rpv_bdy
    block = 2
  []
  [secondary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'rpv_inner'
    new_block_id = 10001
    new_block_name = 'secondary_lower'
    input = 2d_mesh
  []
  [primary]
    type = LowerDBlockFromSidesetGenerator
    sidesets = 'core_outer'
    new_block_id = 10000
    new_block_name = 'primary_lower'
    input = secondary
  []
  allow_renumbering = false
[]

[Variables]
  [Tsolid]
    initial_condition = 500
  []
  [lm]
    order = FIRST
    family = LAGRANGE
    block = 'secondary_lower'
  []
[]

[Kernels]
  [heat_source]
    type = CoupledForce
    variable = Tsolid
    block = '${core_blocks}'
    v = power_density
  []
  [heat_conduction]
    type = HeatConduction
    variable = Tsolid
  []
[]

[BCs]
  [RPV_out_BC] # k \nabla T = h (T- T_inf) at RPV outer boundary
    type = ConvectiveFluxFunction # (Robin BC)
    variable = Tsolid
    boundary = 'outer' # outer RPV
    coefficient = ${rpv_outer_htc}
    T_infinity = ${rpv_outer_Tinf}
  []
[]

[UserObjects]
  [radiation]
    type = GapFluxModelRadiation
    temperature = Tsolid
    boundary = 'rpv_inner'
    primary_emissivity = 0.8
    secondary_emissivity = 0.8
  []
  [conduction]
    type = GapFluxModelConduction
    temperature = Tsolid
    boundary = 'rpv_inner'
    gap_conductivity = 0.1
  []
[]

[Constraints]
  [ced]
    type = ModularGapConductanceConstraint
    variable = lm
    secondary_variable = Tsolid
    primary_boundary = 'core_outer'
    primary_subdomain = 10000
    secondary_boundary = 'rpv_inner'
    secondary_subdomain = 10001
    gap_flux_models = 'radiation conduction'
    gap_geometry_type = 'CYLINDER'
  []
[]

[AuxVariables]
  [power_density]
    block = '${core_blocks}'
    initial_condition = 50e3
  []
[]

[Materials]
  [simple_mat]
    type = HeatConductionMaterial
    thermal_conductivity = 34.6 # W/m/K
  []
[]

[Postprocessors]
  [Tcore_avg]
    type = ElementAverageValue
    variable = Tsolid
    block = '${core_blocks}'
  []
  [Tcore_max]
    type = ElementExtremeValue
    value_type = max
    variable = Tsolid
    block = '${core_blocks}'
  []
  [Tcore_min]
    type = ElementExtremeValue
    value_type = min
    variable = Tsolid
    block = '${core_blocks}'
  []
  [Trpv_avg]
    type = ElementAverageValue
    variable = Tsolid
    block = '${rpv_blocks}'
  []
  [Trpv_max]
    type = ElementExtremeValue
    value_type = max
    variable = Tsolid
    block = '${rpv_blocks}'
  []
  [Trpv_min]
    type = ElementExtremeValue
    value_type = min
    variable = Tsolid
    block = '${rpv_blocks}'
  []
  [ptot]
    type = ElementIntegralVariablePostprocessor
    variable = power_density
    block = '${core_blocks}'
  []
  [rpv_convective_out]
    type = ConvectiveHeatTransferSideIntegral
    T_solid = Tsolid
    boundary = 'outer' # outer RVP
    T_fluid = ${rpv_outer_Tinf}
    htc = ${rpv_outer_htc}
  []
  [heat_balance] # should be equal to 0 upon convergence
    type = ParsedPostprocessor
    expression = '(rpv_convective_out - ptot) / ptot'
    pp_names = 'rpv_convective_out ptot'
  []
[]

[Preconditioning]
  [smp]
    type = SMP
    full = true
  []
[]

[VectorPostprocessors]
  [NodalTemperature]
    type = NodalValueSampler
    sort_by = id
    boundary = 'rpv_inner core_outer'
    variable = 'Tsolid'
  []
[]

[Executioner]
  type = Steady

  petsc_options = '-snes_converged_reason -pc_svd_monitor'
  petsc_options_iname = '-pc_type -pc_factor_mat_solver_package -mat_mffd_err -pc_factor_shift_type -pc_factor_shift_amount'
  petsc_options_value = ' lu       superlu_dist                  1e-5          NONZERO               1e-15'
  snesmf_reuse_base = false

  nl_rel_tol = 1e-10
  nl_abs_tol = 1e-10
  l_max_its = 100

  line_search = none
[]

[Outputs]
  exodus = false
  csv = true
[]

Gap geometry types
Input Parameters
Input Files
References