GasGapConductance

Stores computed gap conductance for gas-filled gap.

note:Often Created by an Action

This object can be set up automatically by using the Thermal Contact LWR Action action.

Theory related to gap heat transfer can be found in Gap Plenum Models. The following describes specific instructions how to setup the models.

Gap Conductance Model

The default values are contact_coef=10.0 and roughness_coef=1.5. To utilize the Toptan model by Toptan et al. (2020), set gap_conductance_model=TOPTAN.


[thermal_contact]
  ...
  gap_conductance_model = TOPTAN
  ...
[]

Fill Gas Thermal Conductivity

Two modeling options are available in BISON to compute the fill gas thermal conductivity of each constituent and its dependence on temperature and/or pressure.

DEFAULT, a temperature-dependent model from MATPRO (Allison et al., 1993)

[ThermalContact<<<{"href": "../../syntax/Modules/HeatTransfer/ThermalContact/index.html"}>>>]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = 3
    secondary = 2
    plenum_pressure = plenum_pressure
    initial_gas_types = He
    initial_fractions = 1
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
    jumpdistance_primary = 0.0
    jumpdistance_secondary = 0.0
  []
[]

ADVANCED, a temperature- and pressure-dependent model (Tournier and El-Genk, 2008; Toptan et al., 2019)

Add the line

gas_thermal_conductivity_model = ADVANCED

to the input block shown above.

Varying Fill Gas Fractions

See Gas Mixture for syntax regarding varying the fill gas as a function of time.

Temperature Jump Distance

Two modeling options are available in BISON to compute the temperature jump distance and its dependence on the gas properties.

LANNING, Kennard's model based on a review by Lanning and Hann (1975)

The Kennard coefficient, kennard_coefficient is 5756 (default).

[ThermalContact<<<{"href": "../../syntax/Modules/HeatTransfer/ThermalContact/index.html"}>>>]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = cladInSurf
    secondary = fuelOutSurf
    jump_distance_model = LANNING
    plenum_pressure = plenumPressure
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
  []
[]

TOPTAN, Kennard's model based on a review by Toptan et al. (2019)

The Kennard coefficient, kennard_coefficient is 0.2173 for the monatomic gases, 0.1149 for the diatomic gases, and 0.1242 for the polyatomic gases.

[ThermalContact<<<{"href": "../../syntax/Modules/HeatTransfer/ThermalContact/index.html"}>>>]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = cladInSurf
    secondary = fuelOutSurf
    jump_distance_model = TOPTAN
    kennard_coefficient = 0.2173
    plenum_pressure = plenumPressure
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
  []
[]

Thermal Accommodation Coefficient

Two modeling options are available in BISON to compute the thermal accommodation coefficient and its dependence on the gas properties.

DEFAULT, a model from MATPRO (Allison et al., 1993) based on Lanning and Hann (1975)

[ThermalContact<<<{"href": "../../syntax/Modules/HeatTransfer/ThermalContact/index.html"}>>>]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = cladInSurf
    secondary = fuelOutSurf
    jump_distance_model = LANNING
    plenum_pressure = plenumPressure
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
  []
[]

TOPTAN, a model that is recommended by Toptan et al. (2019).

[ThermalContact<<<{"href": "../../syntax/Modules/HeatTransfer/ThermalContact/index.html"}>>>]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = cladInSurf
    secondary = fuelOutSurf
    jump_distance_model = LANNING
    thermal_accommodation_model = TOPTAN
    plenum_pressure = plenumPressure
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
  []
[]

Meyer's Hardness of Cladding

The default value of the Meyer hardness is 680MN/m $var element = document.getElementById("moose-equation-6bb58687-d610-4e69-9705-f891d7420049");katex.render("^2", element, {displayMode:false,throwOnError:false});$ . Alternatively, the following temperature-dependent correlation (Hagrman et al., 1980) is available in the code.

[ThermalContact<<<{"href": "../../syntax/Modules/HeatTransfer/ThermalContact/index.html"}>>>]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = 3
    secondary = 2
    roughness_primary = 2e-6
    roughness_secondary = 2e-6
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
    min_gap = 1e-5
    meyer_hardness_model = MATPRO
    quadrature = true
    tangential_tolerance = 1e-5
    contact_pressure = contact_pressure
    warnings = true
  []
[]

Input Parameters

gap_kThermal conductivity variable across the gap.
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:Thermal conductivity variable across the gap.
variableTemperature variable
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:Temperature variable

Required Parameters

appended_property_nameName appended to material properties to make them unique
C++ Type:std::string
Controllable:No
Description:Name appended to material properties to make them unique
blockThe list of blocks (ids or names) that this object will be applied
C++ Type:std::vector<SubdomainName>
Controllable:No
Description:The list of blocks (ids or names) that this object will be applied
boundaryThe list of boundaries (ids or names) from the mesh where this object applies
C++ Type:std::vector<BoundaryName>
Controllable:No
Description:The list of boundaries (ids or names) from the mesh where this object applies
computeTrueWhen false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the MaterialBase via MaterialBasePropertyInterface::getMaterialBase(). Non-computed MaterialBases are not sorted for dependencies.
Default:True
C++ Type:bool
Controllable:No
Description:When false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the MaterialBase via MaterialBasePropertyInterface::getMaterialBase(). Non-computed MaterialBases are not sorted for dependencies.
conductivity_namethermal_conductivityThe name of the MaterialProperty associated with conductivity ("thermal_conductivity" in the case of heat conduction).
Default:thermal_conductivity
C++ Type:MaterialPropertyName
Unit:(no unit assumed)
Controllable:No
Description:The name of the MaterialProperty associated with conductivity ("thermal_conductivity" in the case of heat conduction).
constant_onNONEWhen ELEMENT, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps.When SUBDOMAIN, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps. Evaluations on element qps will be skipped
Default:NONE
C++ Type:MooseEnum
Options:NONE, ELEMENT, SUBDOMAIN
Controllable:No
Description:When ELEMENT, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps.When SUBDOMAIN, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps. Evaluations on element qps will be skipped
contact_coef10The leading coefficient on the solid-solid conduction relation (1/sqrt(m)).
Default:10
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The leading coefficient on the solid-solid conduction relation (1/sqrt(m)).
contact_pressureThe contact pressure variable.
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:The contact pressure variable.
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
declare_suffixAn optional suffix parameter that can be appended to any declared 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 declared properties. The suffix will be prepended with a '_' character.
emissivity_primary1The emissivity of the primary surface
Default:1
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The emissivity of the primary surface
emissivity_secondary1The emissivity of the secondary surface
Default:1
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The emissivity of the secondary surface
external_pressure0Input external pressure in Pascals.
Default:0
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Input external pressure in Pascals.
gap_conductance_modelDEFAULTGap conductance model: DEFAULT=computed according to the original model;TOPTAN=computed according to Toptan et al., 2020
Default:DEFAULT
C++ Type:MooseEnum
Options:DEFAULT, TOPTAN
Controllable:No
Description:Gap conductance model: DEFAULT=computed according to the original model;TOPTAN=computed according to Toptan et al., 2020
gap_geometry_typeGap calculation type.
C++ Type:MooseEnum
Options:PLATE, CYLINDER, SPHERE
Controllable:No
Description:Gap calculation type.
gap_tempTemperature on the other side of the gap
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:Temperature on the other side of the gap
gas_mixtureThe name of the VectorPostprocessor that will compute the gas mixture.
C++ Type:VectorPostprocessorName
Unit:(no unit assumed)
Controllable:No
Description:The name of the VectorPostprocessor that will compute the gas mixture.
gas_thermal_conductivity_modelDEFAULTFill gas thermal conductivity model: DEFAULT=traditional model from MATPRO-11, =f(T));ADVANCED=model from Toptan et al. (2019), =f(T,P)
Default:DEFAULT
C++ Type:MooseEnum
Options:DEFAULT, ADVANCED
Controllable:No
Description:Fill gas thermal conductivity model: DEFAULT=traditional model from MATPRO-11, =f(T));ADVANCED=model from Toptan et al. (2019), =f(T,P)
gascond_scalef1Scaling factor for gas conductivity.
Default:1
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Scaling factor for gas conductivity.
jump_distance_modelDIRECTJump distance model: DIRECT=specify distances directly;LANNING=computed as a function of gas properties (Lanning and Hahn, 1975)TOPTAN=computed as a function of gas properties (Toptan et al., 2019)
Default:DIRECT
C++ Type:MooseEnum
Options:DIRECT, LANNING, TOPTAN
Controllable:No
Description:Jump distance model: DIRECT=specify distances directly;LANNING=computed as a function of gas properties (Lanning and Hahn, 1975)TOPTAN=computed as a function of gas properties (Toptan et al., 2019)
jumpdistance_primary0The temperature jump distance for the primary surface (m).
Default:0
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The temperature jump distance for the primary surface (m).
jumpdistance_secondary0The temperature jump distance for the secondary surface (m).
Default:0
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The temperature jump distance for the secondary surface (m).
layer_thicknessThe layer thickness variable computed in LayerThickness auxiliary kernel
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:The layer thickness variable computed in LayerThickness auxiliary kernel
max_gap1e+06A maximum gap (denominator) size
Default:1e+06
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:A maximum gap (denominator) size
meyer_hardness6.8e+08The Meyer hardness of the softer material (Pa).
Default:6.8e+08
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The Meyer hardness of the softer material (Pa).
meyer_hardness_modelDIRECTMeyer hardness model of the softer material: DIRECT=specify hardness directly;MATPRO=computed as a function of temperature
Default:DIRECT
C++ Type:MooseEnum
Options:DIRECT, MATPRO
Controllable:No
Description:Meyer hardness model of the softer material: DIRECT=specify hardness directly;MATPRO=computed as a function of temperature
min_gap1e-06A minimum gap (denominator) size
Default:1e-06
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:A minimum gap (denominator) size
min_gap_order0Order of the Taylor expansion below min_gap
Default:0
C++ Type:unsigned int
Controllable:No
Description:Order of the Taylor expansion below min_gap
plenum_pressureThe name of the plenum_pressure postprocessor value.
C++ Type:PostprocessorName
Unit:(no unit assumed)
Controllable:No
Description:The name of the plenum_pressure postprocessor value.
roughness_coef1.5The coefficient for the roughness summation.
Default:1.5
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The coefficient for the roughness summation.
roughness_primary1e-06The roughness of the primary surface (m).
Default:1e-06
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The roughness of the primary surface (m).
roughness_secondary1e-06The roughness of the secondary surface (m).
Default:1e-06
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The roughness of the secondary surface (m).
secondary_sideTrueWhether the boundary corresponds to the secondary side in mechanical contact.
Default:True
C++ Type:bool
Controllable:No
Description:Whether the boundary corresponds to the secondary side in mechanical contact.
sphere_originOrigin for sphere geometry
C++ Type:libMesh::VectorValue<double>
Unit:(no unit assumed)
Controllable:No
Description:Origin for sphere geometry
stefan_boltzmann5.67037e-08The Stefan-Boltzmann constant
Default:5.67037e-08
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The Stefan-Boltzmann constant
thermal_accommodation_modelDEFAULTThermal accommodation model: DEFAULT=traditional model from Lanning and Hahn (1975);TOPTAN=model from Toptan et al. (2019b).
Default:DEFAULT
C++ Type:MooseEnum
Options:DEFAULT, TOPTAN
Controllable:No
Description:Thermal accommodation model: DEFAULT=traditional model from Lanning and Hahn (1975);TOPTAN=model from Toptan et al. (2019b).
warningsFalseWhether to output warning messages concerning nodes not being found
Default:False
C++ Type:bool
Controllable:No
Description:Whether to output warning messages concerning nodes not being found

Optional 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
kennard_coefficient5756Nominal leading model coefficient for LANNING.
Default:5756
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Nominal leading model coefficient for LANNING.
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_meshTrueWhether 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:True
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

gap_conductivity1The thermal conductivity of the gap material
Default:1
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The thermal conductivity of the gap material
gap_conductivity_functionThermal conductivity of the gap material as a function. Multiplied by gap_conductivity.
C++ Type:FunctionName
Unit:(no unit assumed)
Controllable:No
Description:Thermal conductivity of the gap material as a function. Multiplied by gap_conductivity.
gap_conductivity_function_variableVariable to be used in the gap_conductivity_function in place of time
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:Variable to be used in the gap_conductivity_function in place of time

Gap Conductivity Parameters

gap_distanceDistance across the gap
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:Distance across the gap

Gap Size Parameters

orderFIRSTThe finite element order
Default:FIRST
C++ Type:MooseEnum
Options:CONSTANT, FIRST, SECOND, THIRD, FOURTH
Controllable:No
Description:The finite element order
quadratureFalseWhether or not to do quadrature point based gap heat transfer. If this is true then gap_distance and gap_temp should NOT be provided (and will be ignored); however, paired_boundary and variable are then required.
Default:False
C++ Type:bool
Controllable:No
Description:Whether or not to do quadrature point based gap heat transfer. If this is true then gap_distance and gap_temp should NOT be provided (and will be ignored); however, paired_boundary and variable are then required.

Integration Parameters

output_propertiesList of material properties, from this material, to output (outputs must also be defined to an output type)
C++ Type:std::vector<std::string>
Controllable:No
Description:List of material properties, from this material, to output (outputs must also be defined to an output type)
outputsnone Vector of output names where you would like to restrict the output of variables(s) associated with this object
Default:none
C++ Type:std::vector<OutputName>
Controllable:No
Description:Vector of output names where you would like to restrict the output of variables(s) associated with this object

Outputs Parameters

paired_boundaryThe boundary to be penetrated
C++ Type:BoundaryName
Controllable:No
Description:The boundary to be penetrated

Gap Surface Definition 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

References

C. M. Allison, G. A. Berna, R. Chambers, E. W. Coryell, K. L. Davis, D. L. Hagrman, D. T. Hagrman, N. L. Hampton, J. K. Hohorst, R. E. Mason, M. L. McComas, K. A. McNeil, R. L. Miller, C. S. Olsen, G. A. Reymann, and L. J. Siefken. SCDAP/RELAP5/MOD3.1 code manual, volume IV: MATPRO-A library of materials properties for light-water-reactor accident analysis. Technical Report NUREG/CR-6150, EGG-2720, Idaho National Engineering Laboratory, 1993.

@TECHREPORT{hagrman93,
    author = "Allison, C. M. and Berna, G. A. and Chambers, R. and Coryell, E. W. and Davis, K. L. and Hagrman, D. L. and Hagrman, D. T. and Hampton, N. L. and Hohorst, J. K. and Mason, R. E. and McComas, M. L. and McNeil, K. A. and Miller, R. L. and Olsen, C. S. and Reymann, G. A. and Siefken, L. J.",
    editor = "Hagrman, D. T.",
    title = "{SCDAP/RELAP5/MOD3.1} Code Manual, Volume {IV}: {MATPRO}-{A} Library of Materials Properties for Light-Water-Reactor Accident Analysis",
    institution = "Idaho National Engineering Laboratory",
    year = "1993",
    number = "NUREG/CR-6150, EGG-2720"
}

D L Hagrman, G A Reymann, and R E Manson. MATPRO-Version 11 (rev. 1): A Handbook of Materials Properties for Use in the Analysis of Light Water Reactor Fuel Rod Behavior. USNRC Report NUREG/CR-0497, TREE-1290, Idaho National Engineering Laboratories, February 1980. doi:10.2172/6442256.

@techreport{matpro11,
    Author = "Hagrman, D L and Reymann, G A and Manson, R E",
    Institution = "Idaho National Engineering Laboratories",
    Month = "February",
    Number = "NUREG/CR-0497, TREE-1290",
    Title = "{MATPRO-Version 11 (rev. 1): A Handbook of Materials Properties for Use in the Analysis of Light Water Reactor Fuel Rod Behavior}",
    Type = "USNRC Report",
    Doi = "10.2172/6442256",
    Year = "1980"
}

D. D. Lanning and C. R. Hann. Review of methods applicable to the calculation of gap conductance in zircaloy-clad uo2 fuel rods. Technical Report BWNL-1894, UC-78B, Pacific Northwest National Laboratory, 1975.

@TECHREPORT{lanning:1975,
    author = "Lanning, D. D. and Hann, C. R.",
    title = "Review of methods applicable to the calculation of gap conductance in zircaloy-clad UO2 fuel rods",
    year = "1975",
    number = "BWNL-1894, UC-78B",
    publisher = "Pacific Northwest National Laboratory",
    institution = "Pacific Northwest National Laboratory"
}

A Toptan, D J Kropaczek, and M N Avramova. Gap conductance modeling I: theoretical considerations for single- and multi-component gases in curvilinear coordinates. Nuclear Engineering and Design, 353:110283, 2019. doi:10.1016/j.nucengdes.2019.110283.

@article{toptan2019b,
    author = "Toptan, A and Kropaczek, D J and Avramova, M N",
    title = "Gap conductance modeling {I}: Theoretical considerations for single- and multi-component gases in curvilinear coordinates",
    Journal = "Nuclear Engineering and Design",
    Volume = "353",
    Pages = "110283",
    Doi = "10.1016/j.nucengdes.2019.110283",
    Year = "2019"
}

A Toptan, D J Kropaczek, and M N Avramova. On the validity of the dilute gas assumption for gap conductance calculations in nuclear fuel performance codes. Nuclear Engineering and Design, 350:1–8, 2019. doi:10.1016/j.nucengdes.2019.04.042.

@article{toptan2019a,
    author = "Toptan, A and Kropaczek, D J and Avramova, M N",
    title = "On the validity of the dilute gas assumption for gap conductance calculations in nuclear fuel performance codes",
    Journal = "Nuclear Engineering and Design",
    Volume = "350",
    Pages = "1-8",
    Doi = "10.1016/j.nucengdes.2019.04.042",
    Year = "2019"
}

Aysenur Toptan, Jason D. Hales, Richard L. Williamson, Stephen R. Novascone, Giovanni Pastore, and David J. Kropaczek. Modeling of gap conductance for LWR fuel rods applied in the BISON code. Journal of Nuclear Science and Technology, 57(8):963–974, 2020. doi:10.1080/00223131.2020.1740808.

@article{TOPTAN2020963,
    author = "Toptan, Aysenur and Hales, Jason D. and Williamson, Richard L. and Novascone, Stephen R. and Pastore, Giovanni and Kropaczek, David J.",
    title = "Modeling of gap conductance for {LWR} fuel rods applied in the {BISON} code",
    journal = "Journal of Nuclear Science and Technology",
    year = "2020",
    volume = "57",
    number = "8",
    pages = "963--974",
    issn = "0022-3131",
    doi = "10.1080/00223131.2020.1740808"
}

J-M P Tournier and M S El-Genk. Properties of noble gases and binary mixtures for closed brayton cycle applications. Energy Conversion and Management, 49(3):469–492, 2008. doi:10.1016/j.enconman.2007.06.050.

@article{tournier2008,
    Author = "Tournier, J-M P and El-Genk, M S",
    Title = "Properties of Noble Gases and Binary Mixtures for Closed Brayton Cycle Applications",
    Journal = "Energy Conversion and Management",
    Doi = "10.1016/j.enconman.2007.06.050",
    Volume = "49",
    Number = "3",
    Pages = "469-492",
    Year = "2008"
}

(test/tests/fill_gas_thermal_conductivity/gas_type.i)

[GlobalParams]
  displacements = 'displ_x displ_y displ_z'
[]

[Mesh]
  [mesh]
    type = FileMeshGenerator
    file = twoBlock_geom.e
  []
[]

[Variables]
  [displ_x]
  []
  [displ_y]
  []
  [displ_z]
  []
  [temp]
    initial_condition = 400
  []
[]

[AuxVariables]
  [gap_cond]
    order = CONSTANT
    family = MONOMIAL
  []
[]

[Physics/SolidMechanics/QuasiStatic]
  [all]
    strain = finite
  []
[]

[Kernels]
  [heat]
    type = HeatConduction
    variable = temp
  []
[]

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

[ThermalContact]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = 3
    secondary = 2
    plenum_pressure= plenum_pressure
    initial_gas_types = He
    initial_fractions = 1
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
    jumpdistance_primary = 0.0
    jumpdistance_secondary = 0.0
  []
[]


[BCs]
  [fixed_x]
    type = DirichletBC
    boundary = '1 2 3 4'
    variable = displ_x
    value = 0
  []
  [fixed_y]
    type = DirichletBC
    boundary = '1 2 3 4'
    variable = displ_y
    value = 0
  []
  [fixed_z]
    type = DirichletBC
    boundary = '1 2 3 4'
    variable = displ_z
    value = 0
  []
  [PlenumPressure]
    [plenumPressure]
      boundary = '2 3'
      initial_pressure = 1.039309e8
      startup_time = 0.0
      volume = internalVolume
      temperature = temp_gas
      output = plenum_pressure
      displacements = displ_x
    []
  []
  [temp_far_left]
    type = DirichletBC
    boundary = 1
    variable = temp
    value = 500
  []
  [temp_far_right]
    type = DirichletBC
    boundary = 4
    variable = temp
    value = 400
  []
[]

[Materials]
  [elasticity_tensor]
    type = ComputeIsotropicElasticityTensor
    block = '1 2'
    youngs_modulus = 1e6
    poissons_ratio = .3
  []
  [heat1]
    type = HeatConductionMaterial
    block = '1 2'
    specific_heat = 1.0
    thermal_conductivity = 1.0e8
  []
  [density]
    type = StrainAdjustedDensity
    block = '1 2'
    strain_free_density = 1
  []
  [stress]
    type = ComputeFiniteStrainElasticStress
    block = '1 2'
  []
[]

[Executioner]
  type = Transient
  solve_type = Newton
  line_search = 'none'
  nl_rel_tol = 1e-12
  nl_abs_tol = 1e-5
  l_tol = 0.01
  l_max_its = 10
  start_time = 0.0
  dt = 0.1
  end_time = 0.1
[]

[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
  []
  [avgGapHTC]
    type = SideAverageValue
    boundary = 2
    variable = gap_cond
  []
  [avgGapWidth]
    type = SideAverageValue
    boundary = 2
    variable = penetration
  []
  [internalVolume]
    type = InternalVolume
    boundary = '2 3'
    component = 0
    execute_on = 'initial linear'
  []
  [temp_gas]
    type = SideAverageValue
    boundary = '2 3'
    variable = temp
    execute_on = 'initial linear'
  []
[]

[Outputs]
  exodus = false
  csv = true
[]

(test/tests/temperature_jump_distance/He_legacy.i)

#
# Test Temperature Jump Distance Models
#
# This test exercises 1-D gap heat transfer for a variety of fill gases
# using two different models.
#
# The mesh consists of two element blocks containing one element each.  Each
#   element is a unit cube.
#
[GlobalParams]
  displacements = 'displ_x displ_y displ_z'
[]

[Mesh]
  [mesh]
    type = FileMeshGenerator
    file = twoBlock_plane.e
  []
[]

[Functions]
  [temp]
    type = PiecewiseLinear
    x = '0   1   2'
    y = '500 1500 3000'
  []
[]

[Variables]
  [displ_x]
  []
  [displ_y]
  []
  [displ_z]
  []
  [temp]
    order = FIRST
    family = LAGRANGE
    initial_condition = 400
  []
[]

[AuxVariables]
  [gap_cond]
    order = CONSTANT
    family = MONOMIAL
  []
[]

[Physics/SolidMechanics/QuasiStatic]
  [all]
    strain = finite
  []
[]

[Kernels]
  [heat]
    type = HeatConduction
    variable = temp
  []
[]

[AuxKernels]
  [conductance]
    type = MaterialRealAux
    property = gap_conductance
    variable = gap_cond
    boundary = fuelOutSurf
    execute_on = 'initial linear'
  []
[]

[BCs]
  [fixed_x]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_x
    value = 0
  []
  [fixed_y]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_y
    value = 0
  []
  [fixed_z]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_z
    value = 0
  []
  [PlenumPressure]
    [plenumPressure]
      boundary = 'fuelOutSurf cladInSurf'
      initial_temperature = 400
      initial_pressure = 1.039309e6
      volume = internalVolume
      temperature = temp_gas
      startup_time = 0.0
      displacements = displ_x
    []
  []
  [temp_far_left]
    type = FunctionDirichletBC
    boundary = fuelInSurf
    variable = temp
    function = temp
  []
  [temp_far_right]
    type = DirichletBC
    boundary = cladOutSurf
    variable = temp
    value = 400
  []
[]

[ThermalContact]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = cladInSurf
    secondary = fuelOutSurf
    jump_distance_model = LANNING
    plenum_pressure = plenumPressure
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
  []
[]

[Materials]
  [elasticity_tensor]
    type = ComputeIsotropicElasticityTensor
    block = 'cladBlock fuelBlock'
    youngs_modulus = 1e6
    poissons_ratio = .3
  []
  [stress]
    type = ComputeFiniteStrainElasticStress
    block = 'cladBlock fuelBlock'
  []
  [heat1]
    type = HeatConductionMaterial
    block = 'cladBlock fuelBlock'
    specific_heat = 1.0
    thermal_conductivity = 1.0e8
  []
  [density]
    type = StrainAdjustedDensity
    block = 'cladBlock fuelBlock'
    strain_free_density = 1
  []
[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'
  petsc_options_iname = '-ksp_gmres_restart -pc_type -pc_hypre_type -pc_hypre_boomeramg_max_iter'
  petsc_options_value = '201                hypre    boomeramg      4'
  line_search = 'none'
  nl_abs_tol = 1e-6
  nl_rel_tol = 1e-10
  l_tol = 1e-3
  l_max_its = 100
  start_time = 0.0
  dt = 1e-1
  end_time = 2.0
[]

[Postprocessors]
  [gapHTC]
    type = SideAverageValue
    boundary = fuelOutSurf
    variable = gap_cond
    execute_on = 'initial timestep_end'
  []
  [tempFuelIn]
    type = SideAverageValue
    boundary = fuelInSurf
    variable = temp
    execute_on = 'initial timestep_end'
  []
  [tempCladOut]
    type = SideAverageValue
    boundary = cladOutSurf
    variable = temp
    execute_on = 'initial timestep_end'
  []
  [gapWidth]
    type = SideAverageValue
    boundary = fuelOutSurf
    variable = penetration
    execute_on = 'initial linear'
  []
  [temp_gas]
    type = SideAverageValue
    boundary = 'fuelOutSurf cladInSurf'
    variable = temp
    execute_on = 'initial linear'
  []
  [internalVolume]
    type = InternalVolume
    boundary = 'fuelOutSurf cladInSurf'
    component = 0
    execute_on = 'initial linear'
  []
[]

[Outputs]
  file_base= 'He_legacy'
  exodus = false
  csv = true
[]

(test/tests/temperature_jump_distance/He_toptan.i)

#
# Test Temperature Jump Distance Models
#
# This test exercises 1-D gap heat transfer for a variety of fill gases
# using two different models.
#
# The mesh consists of two element blocks containing one element each.  Each
#   element is a unit cube.
#
[GlobalParams]
  displacements = 'displ_x displ_y displ_z'
[]

[Mesh]
  [mesh]
    type = FileMeshGenerator
    file = twoBlock_plane.e
  []
[]

[Functions]
  [temp]
    type = PiecewiseLinear
    x = '0   1   2'
    y = '500 1500 3000'
  []
[]

[Variables]
  [displ_x]
  []
  [displ_y]
  []
  [displ_z]
  []
  [temp]
    order = FIRST
    family = LAGRANGE
    initial_condition = 400
  []
[]

[AuxVariables]
  [gap_cond]
    order = CONSTANT
    family = MONOMIAL
  []
[]

[Physics/SolidMechanics/QuasiStatic]
  [all]
    strain = finite
  []
[]

[Kernels]
  [heat]
    type = HeatConduction
    variable = temp
  []
[]

[AuxKernels]
  [conductance]
    type = MaterialRealAux
    property = gap_conductance
    variable = gap_cond
    boundary = fuelOutSurf
    execute_on = 'initial linear'
  []
[]

[BCs]
  [fixed_x]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_x
    value = 0
  []
  [fixed_y]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_y
    value = 0
  []
  [fixed_z]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_z
    value = 0
  []
  [PlenumPressure]
    [plenumPressure]
      boundary = 'fuelOutSurf cladInSurf'
      initial_temperature = 400
      initial_pressure = 1.039309e6
      volume = internalVolume
      temperature = temp_gas
      startup_time = 0.0
      displacements = displ_x
    []
  []
  [temp_far_left]
    type = FunctionDirichletBC
    boundary = fuelInSurf
    variable = temp
    function = temp
  []
  [temp_far_right]
    type = DirichletBC
    boundary = cladOutSurf
    variable = temp
    value = 400
  []
[]

[ThermalContact]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = cladInSurf
    secondary = fuelOutSurf
    jump_distance_model = TOPTAN
    kennard_coefficient = 0.2173
    plenum_pressure = plenumPressure
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
  []
[]

[Materials]
  [elasticity_tensor]
    type = ComputeIsotropicElasticityTensor
    block = 'cladBlock fuelBlock'
    youngs_modulus = 1e6
    poissons_ratio = .3
  []
  [stress]
    type = ComputeFiniteStrainElasticStress
    block = 'cladBlock fuelBlock'
  []
  [heat1]
    type = HeatConductionMaterial
    block = 'cladBlock fuelBlock'
    specific_heat = 1.0
    thermal_conductivity = 1.0e8
  []
  [density]
    type = StrainAdjustedDensity
    block = 'cladBlock fuelBlock'
    strain_free_density = 1
  []
[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'
  petsc_options_iname = '-ksp_gmres_restart -pc_type -pc_hypre_type -pc_hypre_boomeramg_max_iter'
  petsc_options_value = '201                hypre    boomeramg      4'
  line_search = 'none'
  nl_abs_tol = 1e-6
  nl_rel_tol = 1e-10
  l_tol = 1e-3
  l_max_its = 100
  start_time = 0.0
  dt = 1e-1
  end_time = 2.0
[]

[Postprocessors]
  [gapHTC]
    type = SideAverageValue
    boundary = fuelOutSurf
    variable = gap_cond
    execute_on = 'initial timestep_end'
  []
  [tempFuelIn]
    type = SideAverageValue
    boundary = fuelInSurf
    variable = temp
    execute_on = 'initial timestep_end'
  []
  [tempCladOut]
    type = SideAverageValue
    boundary = cladOutSurf
    variable = temp
    execute_on = 'initial timestep_end'
  []
  [gapWidth]
    type = SideAverageValue
    boundary = fuelOutSurf
    variable = penetration
    execute_on = 'initial linear'
  []
  [temp_gas]
    type = SideAverageValue
    boundary = 'fuelOutSurf cladInSurf'
    variable = temp
    execute_on = 'initial linear'
  []
  [internalVolume]
    type = InternalVolume
    boundary = 'fuelOutSurf cladInSurf'
    component = 0
    execute_on = 'initial linear'
  []
[]

[Outputs]
  file_base = 'He_toptan'
  exodus = false
  csv = true
[]

(test/tests/thermal_accommodation_coeff/He_legacy.i)

#
# Test Thermal Accommodation Coefficient Models
#
# This test exercises 1-D gap heat transfer for a variety of fill gases
# using two different models. Note that the thermal accommodation coefficient is
# only computed when temperature jump distance are computed. LANNING model (legacy)
# is utilized for the jump distance calculations in this analysis.
#
# The mesh consists of two element blocks containing one element each.  Each
#   element is a unit cube.
#
# The conductivity of both blocks is large to achieve a uniform temperature
#  across each block. The temperature of the far left boundary
#  is ramped from 500 to 3000 over one time unit, and then held fixed for an additional
#  time unit.
#
# For comparison, at time=2.0
#           legacy            toptan
# He    512.7214722158   512.94697860186
# Ne
# Ar     64.3767736003    64.38000412746
# Kr     41.4861290899    41.48667793655
# Xe     26.4201415423    26.42020030259
# mix1   86.5496081564    86.54970913890
# mix2  137.8021454059   137.80175970234
#
# note that
# for mix1, initial_gas_fractions='0.25 0.0 0.25 0.25 0.25 0 0 0 0 0 0'
# for mix2, initial_gas_fractions='0.2 0.0 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0 0'
# for mix3, initial_gas_fractions='0.2 0.2 0.2 0.2 0.2 0 0 0 0 0 0'
#
[GlobalParams]
  displacements = 'displ_x displ_y displ_z'
[]

[Mesh]
  [mesh]
    type = FileMeshGenerator
    file = twoBlock_plane.e
  []
[]

[Functions]
  [temp]
    type = PiecewiseLinear
    x = '0   1   2'
    y = '500 1500 3000'
  []
[]

[Variables]
  [displ_x]
  []
  [displ_y]
  []
  [displ_z]
  []
  [temp]
    order = FIRST
    family = LAGRANGE
    initial_condition = 400
  []
[]

[AuxVariables]
  [gap_cond]
    order = CONSTANT
    family = MONOMIAL
  []
[]

[Physics/SolidMechanics/QuasiStatic]
  [all]
    strain = finite
  []
[]

[Kernels]
  [heat]
    type = HeatConduction
    variable = temp
  []
[]

[AuxKernels]
  [conductance]
    type = MaterialRealAux
    property = gap_conductance
    variable = gap_cond
    boundary = fuelOutSurf
    execute_on = 'initial linear'
  []
[]

[BCs]
  [fixed_x]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_x
    value = 0
  []
  [fixed_y]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_y
    value = 0
  []
  [fixed_z]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_z
    value = 0
  []
  [PlenumPressure]
    [plenumPressure]
      boundary = 'fuelOutSurf cladInSurf'
      initial_temperature = 400
      initial_pressure = 1.039309e7
      volume = internalVolume
      temperature = temp_gas
      startup_time = 0.0
      displacements = displ_x
    []
  []
  [temp_far_left]
    type = FunctionDirichletBC
    boundary = fuelInSurf
    variable = temp
    function = temp
  []
  [temp_far_right]
    type = DirichletBC
    boundary = cladOutSurf
    variable = temp
    value = 400
  []
[]

[ThermalContact]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = cladInSurf
    secondary = fuelOutSurf
    jump_distance_model = LANNING
    plenum_pressure = plenumPressure
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
  []
[]

[Materials]
  [elasticity_tensor]
    type = ComputeIsotropicElasticityTensor
    block = 'cladBlock fuelBlock'
    youngs_modulus = 1e6
    poissons_ratio = .3
  []
  [stress]
    type = ComputeFiniteStrainElasticStress
    block = 'cladBlock fuelBlock'
  []
  [heat1]
    type = HeatConductionMaterial
    block = 'cladBlock fuelBlock'
    specific_heat = 1.0
    thermal_conductivity = 1.0e8
  []
  [density]
    type = StrainAdjustedDensity
    block = 'cladBlock fuelBlock'
    strain_free_density = 1
  []
[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'
  petsc_options_iname = '-ksp_gmres_restart -pc_type -pc_hypre_type -pc_hypre_boomeramg_max_iter'
  petsc_options_value = '201                hypre    boomeramg      4'
  line_search = 'none'
  nl_abs_tol = 1e-6
  nl_rel_tol = 1e-10
  l_tol = 1e-3
  l_max_its = 100
  start_time = 0.0
  dt = 1e-1
  end_time = 2.0
[]

[Postprocessors]
  [gapHTC]
    type = SideAverageValue
    boundary = fuelOutSurf
    variable = gap_cond
    execute_on = 'initial timestep_end'
  []
  [tempFuelIn]
    type = SideAverageValue
    boundary = fuelInSurf
    variable = temp
    execute_on = 'initial timestep_end'
  []
  [tempCladOut]
    type = SideAverageValue
    boundary = cladOutSurf
    variable = temp
    execute_on = 'initial timestep_end'
  []
  [gapWidth]
    type = SideAverageValue
    boundary = fuelOutSurf
    variable = penetration
    execute_on = 'initial linear'
  []
  [temp_gas]
    type = SideAverageValue
    boundary = 'fuelOutSurf cladInSurf'
    variable = temp
    execute_on = 'initial linear'
  []
  [internalVolume]
    type = InternalVolume
    boundary = 'fuelOutSurf cladInSurf'
    component = 0
    execute_on = 'initial linear'
  []
[]

[Outputs]
  file_base = 'He'
  exodus = false
  csv = true
[]

(test/tests/thermal_accommodation_coeff/He_toptan.i)

#
# Test Thermal Accommodation Coefficient Models
#
# This test exercises 1-D gap heat transfer for a variety of fill gases
# using two different models. Note that the thermal accommodation coefficient is
# only computed when temperature jump distance are computed. LANNING model (legacy)
# is utilized for the jump distance calculations in this analysis.
#
# The mesh consists of two element blocks containing one element each.  Each
#   element is a unit cube.
#
# The conductivity of both blocks is large to achieve a uniform temperature
#  across each block. The temperature of the far left boundary
#  is ramped from 500 to 3000 over one time unit, and then held fixed for an additional
#  time unit.
#
# For comparison, at time=2.0
#           legacy            toptan
# He    512.7214722158   512.94697860186
# Ne
# Ar     64.3767736003    64.38000412746
# Kr     41.4861290899    41.48667793655
# Xe     26.4201415423    26.42020030259
# mix1   86.5496081564    86.54970913890
# mix2  137.8021454059   137.80175970234
#
# note that
# for mix1, initial_gas_fractions='0.25 0.0 0.25 0.25 0.25 0 0 0 0 0 0'
# for mix2, initial_gas_fractions='0.2 0.0 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0 0'
# for mix3, initial_gas_fractions='0.2 0.2 0.2 0.2 0.2 0 0 0 0 0 0'
#
[GlobalParams]
  displacements = 'displ_x displ_y displ_z'
[]

[Mesh]
  [mesh]
    type = FileMeshGenerator
    file = twoBlock_plane.e
  []
[]

[Functions]
  [temp]
    type = PiecewiseLinear
    x = '0   1   2'
    y = '500 1500 3000'
  []
[]

[Variables]
  [displ_x]
  []
  [displ_y]
  []
  [displ_z]
  []
  [temp]
    order = FIRST
    family = LAGRANGE
    initial_condition = 400
  []
[]

[AuxVariables]
  [gap_cond]
    order = CONSTANT
    family = MONOMIAL
  []
[]

[Physics/SolidMechanics/QuasiStatic]
  [all]
    strain = finite
  []
[]

[Kernels]
  [heat]
    type = HeatConduction
    variable = temp
  []
[]

[AuxKernels]
  [conductance]
    type = MaterialRealAux
    property = gap_conductance
    variable = gap_cond
    boundary = fuelOutSurf
    execute_on = 'initial linear'
  []
[]

[BCs]
  [fixed_x]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_x
    value = 0
  []
  [fixed_y]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_y
    value = 0
  []
  [fixed_z]
    type = DirichletBC
    boundary = 'fuelInSurf fuelOutSurf cladInSurf cladOutSurf'
    variable = displ_z
    value = 0
  []
  [PlenumPressure]
    [plenumPressure]
      boundary = 'fuelOutSurf cladInSurf'
      initial_temperature = 400
      initial_pressure = 1.039309e7
      volume = internalVolume
      temperature = temp_gas
      startup_time = 0.0
      displacements = displ_x
    []
  []
  [temp_far_left]
    type = FunctionDirichletBC
    boundary = fuelInSurf
    variable = temp
    function = temp
  []
  [temp_far_right]
    type = DirichletBC
    boundary = cladOutSurf
    variable = temp
    value = 400
  []
[]

[ThermalContact]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = cladInSurf
    secondary = fuelOutSurf
    jump_distance_model = LANNING
    thermal_accommodation_model = TOPTAN
    plenum_pressure = plenumPressure
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
  []
[]

[Materials]
  [elasticity_tensor]
    type = ComputeIsotropicElasticityTensor
    block = 'cladBlock fuelBlock'
    youngs_modulus = 1e6
    poissons_ratio = .3
  []
  [stress]
    type = ComputeFiniteStrainElasticStress
    block = 'cladBlock fuelBlock'
  []
  [heat1]
    type = HeatConductionMaterial
    block = 'cladBlock fuelBlock'
    specific_heat = 1.0
    thermal_conductivity = 1.0e8
  []
  [density]
    type = StrainAdjustedDensity
    block = 'cladBlock fuelBlock'
    strain_free_density = 1
  []
[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'
  petsc_options_iname = '-ksp_gmres_restart -pc_type -pc_hypre_type -pc_hypre_boomeramg_max_iter'
  petsc_options_value = '201                hypre    boomeramg      4'
  line_search = 'none'
  nl_abs_tol = 1e-6
  nl_rel_tol = 1e-10
  l_tol = 1e-3
  l_max_its = 100
  start_time = 0.0
  dt = 1e-1
  end_time = 2.0
[]

[Postprocessors]
  [gapHTC]
    type = SideAverageValue
    boundary = fuelOutSurf
    variable = gap_cond
    execute_on = 'initial timestep_end'
  []
  [tempFuelIn]
    type = SideAverageValue
    boundary = fuelInSurf
    variable = temp
    execute_on = 'initial timestep_end'
  []
  [tempCladOut]
    type = SideAverageValue
    boundary = cladOutSurf
    variable = temp
    execute_on = 'initial timestep_end'
  []
  [gapWidth]
    type = SideAverageValue
    boundary = fuelOutSurf
    variable = penetration
    execute_on = 'initial linear'
  []
  [temp_gas]
    type = SideAverageValue
    boundary = 'fuelOutSurf cladInSurf'
    variable = temp
    execute_on = 'initial linear'
  []
  [internalVolume]
    type = InternalVolume
    boundary = 'fuelOutSurf cladInSurf'
    component = 0
    execute_on = 'initial linear'
  []
[]

[Outputs]
  file_base = 'He_toptan'
  exodus = false
  csv = true
[]

(test/tests/gap_heat_transfer/gap_heat_transfer_contact_pressure2m.i)

#
# 1-D Gap Heat Transfer
#
# This test exercises 1-D gap heat transfer including both gas conductance and
#   increased conductance from contact pressure.
#
# The mesh consists of two element blocks roughly the dimensions of a slice of
#   LWR fuel.  Block 1 is the inner (fuel) block, and block 2 is the outer
#   (clad) block.  The two blocks begin life next to one another.  The
#   temperature is prescribed on both the centerline of the fuel and the outer
#   surface of the clad.  The fuel centerline temperature rises from 300 to 1200
#   over 3 time units.  The outer clad temperature rises from 300 to 600 over
#   one time unit and is held constant from that point on.  Due to thermal
#   expansion, the blocks are in contact at the final time.
#
# A simple analytical solution is possible for the heat flux between the blocks:
#
#  q = (T_left - T_right) * (h_cond + h_contact)
#
#    where: h_cond = k(T)/(gap + min_gap + roughness_coef*(roughness_left + roughness_right))
#           h_contact = Cs*(2*k_left*k_right)/(k_left+k_right)) * 1/(sqrt(delta)*H) * P_contact
#
#             and delta = 0.8*(roughness_left + roughness_right)
#
# For pure helium, BISON currently computes the gas conductivity as:
#
#  gapK(Tavg) = 2.639e-3*Tavg^0.7085
#
# At the final time, the average gas temperature is (6.05142e2 + 6.026945e2)/2
#  giving gapK(150) = 0.24647
#
#
# Given the following parameters:
#            min_gap = 1e-7
#            Cs = 10
#            k_left = 2.5
#            k_right = 16
#            roughness_left = 2e-6
#            roughness_right = 2e-6
#            roughness_coef = 0
#            H = 0.68e9
#            P_contact = 250e6 (approximate)
#
#   at time 3, the heat flux is:
#
#   q = dT * (24647 + 8887) = 82075
#
# The area associated with the flux is 2*pi*h*r:
#   A = 2*pi*0.002*.0041 = 5.15229e-5
#
# q*A = 4.23
#
# The flux post processors give 4.21 and 4.26.
#

[GlobalParams]
  displacements = 'disp_x disp_y'
  order = SECOND
  family = LAGRANGE
[]

[Mesh]
  coord_type = RZ
  [mesh]
    type = FileMeshGenerator
    file = gap_heat_transfer_contact_pressure2.e
  []
[]

[Functions]
  [tempLeft]
    type = PiecewiseLinear
    x = '0   3'
    y = '300 1200'
  []
  [tempRight]
    type = PiecewiseLinear
    x = '0   1'
    y = '300 600'
  []
[]

[Variables]
  [disp_x]
  []

  [disp_y]
  []

  [temp]
    initial_condition = 300
  []
[]

[Physics/SolidMechanics/QuasiStatic]
  [stuff]
    add_variables = false
    strain = SMALL
    incremental = true
    eigenstrain_names = 'thermal_eigenstrain'
    generate_output = 'stress_xx'
    temperature = temp
  []
[]

[Kernels]
  [heat]
    type = HeatConduction
    variable = temp
  []
[]

[BCs]
  [temp_left]
    type = FunctionDirichletBC
    boundary = '1'
    variable = temp
    function = tempLeft
  []

  [temp_right]
    type = FunctionDirichletBC
    boundary = '4'
    variable = temp
    function = tempRight
  []

  [fixed_x]
    type = DirichletBC
    boundary = 1
    variable = disp_x
    value = 0
  []

  [fixed_y]
    type = DirichletBC
    boundary = 5
    variable = disp_y
    value = 0
  []
[]

[Contact]
  [dummy_name]
    primary = 3
    secondary = 2
    penalty = 1e7
    model = frictionless
    tangential_tolerance = 1e-5
  []
[]

[ThermalContact]
  [thermal_contact]
    type = GasGapHeatTransfer
    variable = temp
    primary = 3
    secondary = 2
    roughness_primary = 2e-6
    roughness_secondary = 2e-6
    roughness_coef = 0
    emissivity_primary = 0
    emissivity_secondary = 0
    min_gap = 1e-5
    meyer_hardness_model = MATPRO
    quadrature = true
    tangential_tolerance = 1e-5
    contact_pressure = contact_pressure
    warnings = true
  []
[]


[Materials]
  [leftE]
    type = ComputeIsotropicElasticityTensor
    block = 1
    youngs_modulus = 2e11
    poissons_ratio = 0.345
  []
  [rightE]
    type = ComputeIsotropicElasticityTensor
    block = 2
    youngs_modulus = 7.5e11
    poissons_ratio = 0.3
  []
  [thermal_expansion1]
    type = ComputeThermalExpansionEigenstrain
    block = 1
    thermal_expansion_coeff = 10e-6
    temperature = temp
    stress_free_temperature = 300.0
    eigenstrain_name = thermal_eigenstrain
  []
  [thermal_expansion2]
    type = ComputeThermalExpansionEigenstrain
    block = 2
    thermal_expansion_coeff = 0.0
    temperature = temp
    stress_free_temperature = 300.0
    eigenstrain_name = thermal_eigenstrain
  []
  [fuel_elastic_stress]
    type = ComputeFiniteStrainElasticStress
  []

  [heat1]
    type = HeatConductionMaterial
    block = 1
    specific_heat = 1.0
    thermal_conductivity = 2.5
  []

  [heat2]
    type = HeatConductionMaterial
    block = 2
    specific_heat = 1.0
    thermal_conductivity = 16
  []

  [density]
    type = StrainAdjustedDensity
    block = '1 2'
    strain_free_density = 1.0
  []
[]

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

[Executioner]
  type = Transient
  solve_type = 'PJFNK'
  petsc_options_iname = '-pc_type -pc_factor_mat_solver_package'
  petsc_options_value = 'lu superlu_dist'
  line_search = 'none'
  l_tol = 1e-4
  l_max_its = 40
  start_time = 0.0
  dt = 0.5
  end_time = 3.0
  num_steps = 100
[]

[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]
  file_base = 'gap_heat_transfer_contact_pressure2m_out'
  exodus = false
  csv = true
[]

Gap Conductance Model
Fill Gas Thermal Conductivity
Varying Fill Gas Fractions
Temperature Jump Distance
Thermal Accommodation Coefficient
Meyer ' s Hardness of Cladding
Input Parameters
References