NodeValueAtXFEMInterface

Obtain field values and gradients on the interface.

Overview

The values of field variables on either side of a moving interface are often needed to define the interface velocity. These variables and their gradients might be discontinuous across the interface. The fact that the interface does not lie on the standard quadrature points makes it difficult to get the quantities on the interface using existing functions in MOOSE.

NodeValueAtXFEMInterface provides functions to return the value of a field variable and its gradient on both the positive and negative sides of the interface. It is run on the nodes of the cutting mesh. Typically a node in the cut mesh lies within an element of the finite element mesh, and its location is determined by PointLocator. The value of a field variable at the node location will be obtained by an interpolation of element's (and the overlapping element's) node values and shape functions. The NodeValueAtXFEMInterface object is used by the XFEMMovingInterfaceVelocityBase derived class to calculate the velocity of the interface for moving interface problems.

Example Input File Syntax

[UserObjects<<<{"href": "../../syntax/UserObjects/index.html"}>>>]
  [value_uo]
    type = NodeValueAtXFEMInterface<<<{"description": "Obtain field values and gradients on the interface.", "href": "NodeValueAtXFEMInterface.html"}>>>
    variable<<<{"description": "The name of the variable that this UserObject operates on"}>>> = 'u'
    interface_mesh_cut_userobject<<<{"description": "Name of InterfaceMeshCutUserObject that provides cut locations to this UserObject."}>>> = 'cut_mesh'
    execute_on<<<{"description": "The list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html."}>>> = TIMESTEP_END
    level_set_var<<<{"description": "The name of level set variable used to represent the interface"}>>> = ls
  []
[]

Input Parameters

level_set_varThe name of level set variable used to represent the interface
C++ Type:VariableName
Unit:(no unit assumed)
Controllable:No
Description:The name of level set variable used to represent the interface
variableThe name of the variable that this UserObject operates on
C++ Type:VariableName
Unit:(no unit assumed)
Controllable:No
Description:The name of the variable that this UserObject operates on

Required Parameters

interface_mesh_cut_userobjectName of InterfaceMeshCutUserObject that provides cut locations to this UserObject.
C++ Type:UserObjectName
Controllable:No
Description:Name of InterfaceMeshCutUserObject that provides cut locations to this UserObject.

Optional Parameters

allow_duplicate_execution_on_initialFalseIn the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).
Default:False
C++ Type:bool
Controllable:No
Description:In the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).
execute_onTIMESTEP_ENDThe list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html.
Default:TIMESTEP_END
C++ Type:ExecFlagEnum
Options:XFEM_MARK, NONE, INITIAL, LINEAR, LINEAR_CONVERGENCE, NONLINEAR, NONLINEAR_CONVERGENCE, POSTCHECK, TIMESTEP_END, TIMESTEP_BEGIN, MULTIAPP_FIXED_POINT_END, MULTIAPP_FIXED_POINT_BEGIN, MULTIAPP_FIXED_POINT_CONVERGENCE, FINAL, CUSTOM
Controllable:No
Description:The list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html.
execution_order_group0Execution order groups are executed in increasing order (e.g., the lowest number is executed first). Note that negative group numbers may be used to execute groups before the default (0) group. Please refer to the user object documentation for ordering of user object execution within a group.
Default:0
C++ Type:int
Controllable:No
Description:Execution order groups are executed in increasing order (e.g., the lowest number is executed first). Note that negative group numbers may be used to execute groups before the default (0) group. Please refer to the user object documentation for ordering of user object execution within a group.
force_postauxFalseForces the UserObject to be executed in POSTAUX
Default:False
C++ Type:bool
Controllable:No
Description:Forces the UserObject to be executed in POSTAUX
force_preauxFalseForces the UserObject to be executed in PREAUX
Default:False
C++ Type:bool
Controllable:No
Description:Forces the UserObject to be executed in PREAUX
force_preicFalseForces the UserObject to be executed in PREIC during initial setup
Default:False
C++ Type:bool
Controllable:No
Description:Forces the UserObject to be executed in PREIC during initial setup

Execution Scheduling 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.
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

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

(moose/modules/xfem/test/tests/moving_interface/phase_transition_2d.i)

[GlobalParams]
  order = FIRST
  family = LAGRANGE
[]

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 11
    ny = 1
    xmin = 0.0
    xmax = 20.0
    ymin = 0.0
    ymax = 5.0
    elem_type = QUAD4
  []
[]

[XFEM]
  qrule = volfrac
  output_cut_plane = true
[]

[UserObjects]
  [velocity]
    type = XFEMPhaseTransitionMovingInterfaceVelocity
    diffusivity_at_positive_level_set = 5
    diffusivity_at_negative_level_set = 1
    equilibrium_concentration_jump = 1
    value_at_interface_uo = value_uo
  []
  [value_uo]
    type = NodeValueAtXFEMInterface
    variable = 'u'
    interface_mesh_cut_userobject = 'cut_mesh'
    execute_on = TIMESTEP_END
    level_set_var = ls
  []
  [cut_mesh]
    type = InterfaceMeshCut2DUserObject
    mesh_file = flat_interface_1d.e
    interface_velocity_uo = velocity
    heal_always = true
  []
[]

[Variables]
  [u]
  []
[]

[ICs]
  [ic_u]
    type = FunctionIC
    variable = u
    function = 'if(x<5.01, 2, 1)'
  []
[]

[AuxVariables]
  [ls]
    order = FIRST
    family = LAGRANGE
  []
[]

[Constraints]
  [u_constraint]
    type = XFEMEqualValueAtInterface
    geometric_cut_userobject = 'cut_mesh'
    use_displaced_mesh = false
    variable = u
    value = 2
    alpha = 1e6
  []
[]

[Kernels]
  [diff]
    type = MatDiffusion
    variable = u
    diffusivity = diffusion_coefficient
  []
  [time]
    type = TimeDerivative
    variable = u
  []
[]

[AuxKernels]
  [ls]
    type = MeshCutLevelSetAux
    mesh_cut_user_object = cut_mesh
    variable = ls
    execute_on = 'TIMESTEP_BEGIN'
  []
[]

[Materials]
  [diffusivity_A]
    type = GenericConstantMaterial
    prop_names = A_diffusion_coefficient
    prop_values = 5
  []
  [diffusivity_B]
    type = GenericConstantMaterial
    prop_names = B_diffusion_coefficient
    prop_values = 1
  []
  [diff_combined]
    type = LevelSetBiMaterialReal
    levelset_positive_base = 'A'
    levelset_negative_base = 'B'
    level_set_var = ls
    prop_name = diffusion_coefficient
  []
[]

[BCs]
  # Define boundary conditions
  [left_u]
    type = DirichletBC
    variable = u
    value = 2
    boundary = left
  []

  [right_u]
    type = NeumannBC
    variable = u
    boundary = right
    value = 0
  []
[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'
  petsc_options_iname = '-pc_type'
  petsc_options_value = 'lu'
  line_search = 'none'

  l_tol = 1e-3
  nl_max_its = 15
  nl_rel_tol = 1e-9
  nl_abs_tol = 1e-9

  start_time = 0.0
  dt = 1
  num_steps = 5
  max_xfem_update = 1
[]

[Outputs]
  execute_on = timestep_end
  exodus = true
  perf_graph = true
[]

Overview
Example Input File Syntax
Input Parameters