ElementSubdomainModifier

Overview

The ElementSubdomainModifier modifies an element subdomain ID. This class is inherited by other mesh modifiers, such as CoupledVarThresholdElementSubdomainModifier and TimedSubdomainModifier, which implement different criteria for a subdomain ID to be modified.

The ElementSubdomainModifier can model

Element death (with applications in ablation, fracture, etc.);
Element activation (with applications in additive manufacturing, sintering, solidification, etc.);
Moving interface (with applications in metal oxidation, phase transformation, melt pool, etc.).

The ElementSubdomainModifier only changes the element's subdomain. It inherits from ElementSubdomainModifierBase, which handles the corresponding

Moving boundary/interface nodeset/sideset modification,
Solution reinitialization, and
Stateful material property reinitialization,

all of which are demonstrated below.

Consider a unit square domain decomposed by a vertical line $var element = document.getElementById("moose-equation-e9e0874e-a5b6-435f-bccf-f7eec31382d9");katex.render("x=0.25", element, {displayMode:false,throwOnError:false});$ . The elements on the left side of the vertical line have subdomain ID of 1, and the elements on the right side have subdomain ID of 2. The ElementSubdomainModifier is used to change the subdomain ID from 2 to 1 for elements within a circle of radius 0.5 whose center moves along the bottom side towards the right.

Moving boundary/interface nodeset/sideset modification

note

If the moving boundary is defined completely around a subdomain, or between subdomains, then SidesetAroundSubdomainUpdater may be more useful to use in conjunction with the ElementSubdomainModifier, rather than using the moving_boundaries and moving_boundary_subdomain_pairs parameters in ElementSubdomainModifier.

The change of element subdomains will alter the definitions of certain sidesets and nodesets. The parameters moving_boundaries and moving_boundary_subdomain_pairs can optionally be used to modify the corresponding sidesets/nodesets over the elements that change subdomain. The names of the boundaries are specified in moving_boundaries, and the pair of subdomains that each boundary in moving_boundaries lies between must be specified in the corresponding moving_boundary_subdomain_pairs. The element side from the first subdomain of the pair is added to the boundary.

If the boundaries provided through moving_boundaries already exist, the modifier will attempt to modify the provided sidesets/nodesets whenever an element changes subdomain ID. If the boundaries do not exist, the modifier will create sidesets and nodesets with the provided names.

  [moving_circle]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    moving_boundaries = 'moving_boundary'
    moving_boundary_subdomain_pairs = '1 2'
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []

The evolving nodeset (green) between subdomains 1 and 2, as created by the modifier without an existing boundary.

The modifier only creates and modifies boundaries over elements that change subdomain, so the vertical boundary between subdomains 1 and 2 at $var element = document.getElementById("moose-equation-f257ae56-f18e-4230-a7b3-84c66c02c754");katex.render("x=0.25", element, {displayMode:false,throwOnError:false});$ is not added to the created boundary.

If only one boundary is provided but multiple pairs of subdomains are specified, then all the pairs are applied to the one boundary. Element sides on a subdomain's external boundary can also be added by specifying only one subdomain.

  [ext]
    type = SideSetsAroundSubdomainGenerator
    input = 'right'
    block = 1
    new_boundary = 'moving_boundary'
  []
[]

[MeshModifiers]
  [moving_circle]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    moving_boundaries = 'moving_boundary'
    moving_boundary_subdomain_pairs = '1 2; 1'
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

The evolving sideset (green) around subdomain 1, including the external element sides, from an existing boundary.

Since the update of the moving boundary only occurs over elements that change subdomain, this can be used to update boundaries which do not cover the entirety of a subdomain:

  [moving_circle]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    moving_boundaries = 'right'
    moving_boundary_subdomain_pairs = '1 2'
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []

The evolving sideset (green) around subdomain 1, including the external element sides, from an existing boundary.

Even though the moving_boundary_subdomain_pairs defines the moving boundary to be between subdomains 1 and 2 only, the right side of subdomain 2 remains throughout, as no element sides belong to elements that change subdomain.

Nodal and integrated BCs can be applied on the moving boundary.

Solution reinitialization

By default, all elements that change subdomain ID are reinitialized to the new subdomain's initial condition. Suppose the auxiliary variable $var element = document.getElementById("moose-equation-10f28d1c-7a18-4ddf-8101-b48093f60540");katex.render("u", element, {displayMode:false,throwOnError:false});$ has an initial variable value of $var element = document.getElementById("moose-equation-372c2b82-bf2f-4b44-9e76-66fba7a3ce99");katex.render("1", element, {displayMode:false,throwOnError:false});$ in subdomain 1 and $var element = document.getElementById("moose-equation-9142d439-606e-4716-a892-5cb95a6b1696");katex.render("-0.5", element, {displayMode:false,throwOnError:false});$ in subdomain 2, and the variable value doubles at each timestep in subdomain 1:

[ICs]
  [u_1]
    type = ConstantIC
    variable = 'u'
    value = 1
    block = 1
  []
  [u_2]
    type = ConstantIC
    variable = 'u'
    value = -0.5
    block = 2
  []
[]

[MeshModifiers]
  [moving_circle]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[AuxKernels]
  [phi]
    type = ParsedAux
    variable = 'phi'
    expression = '(x-t)^2+(y)^2-0.5^2'
    use_xyzt = true
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [double_u]
    type = StatefulAux
    variable = 'u'
    coupled = 'u'
    block = 1
  []
[]

The auxiliary variable $var element = document.getElementById("moose-equation-e54bb2b5-2dce-4212-9ff5-0250b5ab289d");katex.render("u", element, {displayMode:false,throwOnError:false});$ is reinitialized to $var element = document.getElementById("moose-equation-ab7245c5-fbbb-4ef2-a8aa-89616b7eb036");katex.render("1", element, {displayMode:false,throwOnError:false});$ , which doubles over the timestep to $var element = document.getElementById("moose-equation-141a02e3-0519-49f9-81a0-b5bd57956202");katex.render("2", element, {displayMode:false,throwOnError:false});$ , for all the elements that change subdomain ID to 1

Stateful material property reinitialization

Similarly, all stateful material properties will be re-initialized when an element changes subdomain ID. Suppose initially the diffusivity is $var element = document.getElementById("moose-equation-96136f3a-79ca-4813-9603-93a4809cf8f5");katex.render("0.5", element, {displayMode:false,throwOnError:false});$ in subdomain 1 and $var element = document.getElementById("moose-equation-c098bfb1-bb93-438f-9427-e9dc237bb3f0");katex.render("-1", element, {displayMode:false,throwOnError:false});$ in subdomain 2, and the diffusivity doubles at each time step in subdomain 1:

[Materials]
  [stateful]
    type = StatefulMaterial
    initial_diffusivity = 0.5
    multiplier = 2
    block = 'left'
    outputs = 'exodus'
  []
  [non_stateful]
    type = GenericConstantMaterial
    prop_names = 'diffusivity'
    prop_values = '-1'
    block = 'right'
    outputs = 'exodus'
  []
[]

The diffusivity is reinitialized to $var element = document.getElementById("moose-equation-01c275dc-c64d-4b6e-8d66-46e716b6da3e");katex.render("0.5", element, {displayMode:false,throwOnError:false});$ , which doubles over the timestep to $var element = document.getElementById("moose-equation-3bd41ee4-5358-4d36-8928-ece3530854d8");katex.render("1", element, {displayMode:false,throwOnError:false});$ , for all the elements that change subdomain ID to 1.

Reinitialization restrictions

Depending on the physics, one may or may not want to reinitialize the solution when an element and its related nodes change subdomain ID. For the below examples, consider a unit square domain decomposed by vertical lines $var element = document.getElementById("moose-equation-88ed5cb7-4756-4eab-bc3e-b8584a6bb23a");katex.render("x=0.3", element, {displayMode:false,throwOnError:false});$ and $var element = document.getElementById("moose-equation-0f2b401f-67db-48ba-a5e3-f5e1cde1ac13");katex.render("x=0.6", element, {displayMode:false,throwOnError:false});$ . The elements on the left have subdomain ID of 1, the elements in the middle have subdomain ID of 2, and the elements on the right have subdomain ID of 3.

The ElementSubdomainModifier is used to change the subdomain ID to 1 for elements within a circle of radius 0.3 whose center moves along the bottom side towards the right, and to subdomain ID 2 for elements within a circle of radius 0.3 whose center moves along the top side towards the right.

An auxiliary variable $var element = document.getElementById("moose-equation-ade06e2f-da8f-4010-8f35-f49ac135ee7f");katex.render("u", element, {displayMode:false,throwOnError:false});$ is defined over the domain, with initial values of 1, 2, and 3 in subdomains 1, 2, and 3 respectively:

[MeshModifiers]
  [moving_circle_bottom]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_1'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [moving_circle_top]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_2'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 2
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

The default behaviour of the modifier is to reinitializate all elements that change subdomain ID.

However, if a list of subdomains (IDs or names) is provided through the parameter reinitialize_subdomains, the reinitialization only occurs if the element's new subdomain ID is in the provided list:

[MeshModifiers]
  [moving_circle_bottom]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_1'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [moving_circle_top]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_2'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 2
    reinitialize_subdomains = '1'
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

Reinitialization of only the elements that change subdomain ID to 1.

If an empty list is given in reinitialize_subdomains, then there is no reinitialization of any elements that change subdomain ID.

[MeshModifiers]
  [moving_circle_bottom]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_1'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    reinitialize_subdomains = ''
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [moving_circle_top]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_2'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 2
    reinitialize_subdomains = ''
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

No reinitialization of any elements that change subdomain ID.

Reinitialization can be further restricted by setting the parameter old_subdomain_reinitialized to false. The modifier will then additionally check the element's old subdomain ID. Reinitialization then only occurs if the old subdomain ID was not in the list provided in the parameter reinitialize_subdomains.

[MeshModifiers]
  [moving_circle_bottom]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_1'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    reinitialize_subdomains = '1 2'
    old_subdomain_reinitialized = false
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [moving_circle_top]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_2'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 2
    reinitialize_subdomains = '1 2'
    old_subdomain_reinitialized = false
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

Reinitialization of only the elements which change subdomain ID from 3, to subdomain IDs 1 or 2

(moose/test/tests/meshmodifiers/element_subdomain_modifier/moving_boundary.i)

[Problem]
  solve = false
[]

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 16
    ny = 16
  []
  [left]
    type = SubdomainBoundingBoxGenerator
    input = 'gen'
    block_id = 1
    bottom_left = '0 0 0'
    top_right = '0.25 1 1'
  []
  [right]
    type = SubdomainBoundingBoxGenerator
    input = 'left'
    block_id = 2
    bottom_left = '0.25 0 0'
    top_right = '1 1 1'
  []
[]

[MeshModifiers]
  [moving_circle]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    moving_boundaries = 'moving_boundary'
    moving_boundary_subdomain_pairs = '1 2'
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[AuxVariables]
  [phi]
    [AuxKernel]
      type = ParsedAux
      expression = '(x-t)^2+(y)^2-0.5^2'
      use_xyzt = true
      execute_on = 'INITIAL TIMESTEP_BEGIN'
    []
  []
[]

[Executioner]
  type = Transient
  dt = 0.3
  num_steps = 3
[]

[Outputs]
  exodus = true
[]

(moose/test/tests/meshmodifiers/element_subdomain_modifier/external_moving_boundary.i)

[Problem]
  solve = false
[]

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 16
    ny = 16
  []
  [left]
    type = SubdomainBoundingBoxGenerator
    input = 'gen'
    block_id = 1
    bottom_left = '0 0 0'
    top_right = '0.25 1 1'
  []
  [right]
    type = SubdomainBoundingBoxGenerator
    input = 'left'
    block_id = 2
    bottom_left = '0.25 0 0'
    top_right = '1 1 1'
  []
  [ext]
    type = SideSetsAroundSubdomainGenerator
    input = 'right'
    block = 1
    new_boundary = 'moving_boundary'
  []
[]

[MeshModifiers]
  [moving_circle]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    moving_boundaries = 'moving_boundary'
    moving_boundary_subdomain_pairs = '1 2; 1'
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[AuxVariables]
  [phi]
    [AuxKernel]
      type = ParsedAux
      expression = '(x-t)^2+(y)^2-0.5^2'
      use_xyzt = true
      execute_on = 'INITIAL TIMESTEP_BEGIN'
    []
  []
[]

[Executioner]
  type = Transient
  dt = 0.3
  num_steps = 3
[]

[Outputs]
  exodus = true
[]

(moose/test/tests/meshmodifiers/element_subdomain_modifier/partial_moving_boundary.i)

[Problem]
  solve = false
[]

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 16
    ny = 16
  []
  [left]
    type = SubdomainBoundingBoxGenerator
    input = 'gen'
    block_id = 1
    bottom_left = '0 0 0'
    top_right = '0.25 1 1'
  []
  [right]
    type = SubdomainBoundingBoxGenerator
    input = 'left'
    block_id = 2
    bottom_left = '0.25 0 0'
    top_right = '1 1 1'
  []
[]

[MeshModifiers]
  [moving_circle]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    moving_boundaries = 'right'
    moving_boundary_subdomain_pairs = '1 2'
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[AuxVariables]
  [phi]
    [AuxKernel]
      type = ParsedAux
      expression = '(x-t)^2+(y)^2-0.5^2'
      use_xyzt = true
      execute_on = 'INITIAL TIMESTEP_BEGIN'
    []
  []
[]

[Executioner]
  type = Transient
  dt = 0.3
  num_steps = 3
[]

[Outputs]
  exodus = true
[]

(moose/test/tests/meshmodifiers/element_subdomain_modifier/initial_condition.i)

[Problem]
  solve = false
[]

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 16
    ny = 16
  []
  [left]
    type = SubdomainBoundingBoxGenerator
    input = 'gen'
    block_id = 1
    block_name = 'left'
    bottom_left = '0 0 0'
    top_right = '0.25 1 1'
  []
  [right]
    type = SubdomainBoundingBoxGenerator
    input = 'left'
    block_id = 2
    block_name = 'right'
    bottom_left = '0.25 0 0'
    top_right = '1 1 1'
  []
[]

[AuxVariables]
  [u]
  []
  [phi]
  []

  # for the 'displaced' test only
  inactive = 'disp_x disp_y'
  [disp_x]
  []
  [disp_y]
  []
[]

[ICs]
  [u_1]
    type = ConstantIC
    variable = 'u'
    value = 1
    block = 1
  []
  [u_2]
    type = ConstantIC
    variable = 'u'
    value = -0.5
    block = 2
  []
[]

[MeshModifiers]
  [moving_circle]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[AuxKernels]
  [phi]
    type = ParsedAux
    variable = 'phi'
    expression = '(x-t)^2+(y)^2-0.5^2'
    use_xyzt = true
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [double_u]
    type = StatefulAux
    variable = 'u'
    coupled = 'u'
    block = 1
  []
[]

[Postprocessors]
  # for the 'subdomain_caching' test only
  active = ''
  [average]
    type = SideAverageValue
    variable = 'u'
    boundary = 'bottom'
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[Executioner]
  type = Transient
  dt = 0.1
  num_steps = 3
[]

[Outputs]
  [out]
    type = Exodus
  []
[]

(moose/test/tests/meshmodifiers/element_subdomain_modifier/stateful_property.i)

[Problem]
  solve = false
[]

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 16
    ny = 16
  []
  [left]
    type = SubdomainBoundingBoxGenerator
    input = 'gen'
    block_id = 1
    block_name = 'left'
    bottom_left = '0 0 0'
    top_right = '0.25 1 1'
  []
  [right]
    type = SubdomainBoundingBoxGenerator
    input = 'left'
    block_id = 2
    block_name = 'right'
    bottom_left = '0.25 0 0'
    top_right = '1 1 1'
  []
[]

[MeshModifiers]
  [moving_circle]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[AuxVariables]
  [phi]
    [AuxKernel]
      type = ParsedAux
      expression = '(x-t)^2+(y)^2-0.5^2'
      use_xyzt = true
      execute_on = 'INITIAL TIMESTEP_BEGIN'
    []
  []
[]

[Materials]
  [stateful]
    type = StatefulMaterial
    initial_diffusivity = 0.5
    multiplier = 2
    block = 'left'
    outputs = 'exodus'
  []
  [non_stateful]
    type = GenericConstantMaterial
    prop_names = 'diffusivity'
    prop_values = '-1'
    block = 'right'
    outputs = 'exodus'
  []
[]

[Executioner]
  type = Transient
  dt = 0.1
  num_steps = 3
[]

[Outputs]
  exodus = true
[]

(moose/test/tests/meshmodifiers/element_subdomain_modifier/reinitialization.i)

[Problem]
  kernel_coverage_check = false
[]

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    xmax = 1
    ymax = 1
    nx = 25
    ny = 25
  []
  [left]
    type = SubdomainBoundingBoxGenerator
    input = 'gen'
    block_id = 1
    bottom_left = '0 0 0'
    top_right = '0.3 1 0'
  []
  [middle]
    type = SubdomainBoundingBoxGenerator
    input = 'left'
    block_id = 2
    bottom_left = '0.3 0 0'
    top_right = '0.6 1 0'
  []
  [right]
    type = SubdomainBoundingBoxGenerator
    input = 'middle'
    block_id = 3
    bottom_left = '0.6 0 0'
    top_right = '1 1 0'
  []
[]

[Variables]
  [u]
  []
[]

[ICs]
  [u_1]
    type = ConstantIC
    variable = 'u'
    value = 1
    block = 1
  []
  [u_2]
    type = ConstantIC
    variable = 'u'
    value = 2
    block = 2
  []
  [u_3]
    type = ConstantIC
    variable = 'u'
    value = 3
    block = 3
  []
[]

[MeshModifiers]
  [moving_circle_bottom]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_1'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [moving_circle_top]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_2'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 2
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[AuxVariables]
  [phi_1]
  []
  [phi_2]
  []
[]

[AuxKernels]
  [phi_1]
    type = ParsedAux
    variable = 'phi_1'
    expression = '(x-t)^2+(y)^2-0.3^2'
    use_xyzt = true
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [phi_2]
    type = ParsedAux
    variable = 'phi_2'
    expression = '(x-t)^2+(y-1)^2-0.3^2'
    use_xyzt = true
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[Executioner]
  type = Transient
  dt = 0.3
  num_steps = 3
[]

[Outputs]
  exodus = true
[]

(moose/test/tests/meshmodifiers/element_subdomain_modifier/reinitialization_into.i)

[Problem]
  kernel_coverage_check = false
[]

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    xmax = 1
    ymax = 1
    nx = 25
    ny = 25
  []
  [left]
    type = SubdomainBoundingBoxGenerator
    input = 'gen'
    block_id = 1
    bottom_left = '0 0 0'
    top_right = '0.3 1 0'
  []
  [middle]
    type = SubdomainBoundingBoxGenerator
    input = 'left'
    block_id = 2
    bottom_left = '0.3 0 0'
    top_right = '0.6 1 0'
  []
  [right]
    type = SubdomainBoundingBoxGenerator
    input = 'middle'
    block_id = 3
    bottom_left = '0.6 0 0'
    top_right = '1 1 0'
  []
[]

[Variables]
  [u]
  []
[]

[ICs]
  [u_1]
    type = ConstantIC
    variable = 'u'
    value = 1
    block = 1
  []
  [u_2]
    type = ConstantIC
    variable = 'u'
    value = 2
    block = 2
  []
  [u_3]
    type = ConstantIC
    variable = 'u'
    value = 3
    block = 3
  []
[]

[MeshModifiers]
  [moving_circle_bottom]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_1'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [moving_circle_top]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_2'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 2
    reinitialize_subdomains = '1'
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[AuxVariables]
  [phi_1]
  []
  [phi_2]
  []
[]

[AuxKernels]
  [phi_1]
    type = ParsedAux
    variable = 'phi_1'
    expression = '(x-t)^2+(y)^2-0.3^2'
    use_xyzt = true
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [phi_2]
    type = ParsedAux
    variable = 'phi_2'
    expression = '(x-t)^2+(y-1)^2-0.3^2'
    use_xyzt = true
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[Executioner]
  type = Transient
  dt = 0.3
  num_steps = 3
[]

[Outputs]
  exodus = true
[]

(moose/test/tests/meshmodifiers/element_subdomain_modifier/no_reinitialization.i)

[Problem]
  kernel_coverage_check = false
[]

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    xmax = 1
    ymax = 1
    nx = 25
    ny = 25
  []
  [left]
    type = SubdomainBoundingBoxGenerator
    input = 'gen'
    block_id = 1
    bottom_left = '0 0 0'
    top_right = '0.3 1 0'
  []
  [middle]
    type = SubdomainBoundingBoxGenerator
    input = 'left'
    block_id = 2
    bottom_left = '0.3 0 0'
    top_right = '0.6 1 0'
  []
  [right]
    type = SubdomainBoundingBoxGenerator
    input = 'middle'
    block_id = 3
    bottom_left = '0.6 0 0'
    top_right = '1 1 0'
  []
[]

[Variables]
  [u]
  []
[]

[ICs]
  [u_1]
    type = ConstantIC
    variable = 'u'
    value = 1
    block = 1
  []
  [u_2]
    type = ConstantIC
    variable = 'u'
    value = 2
    block = 2
  []
  [u_3]
    type = ConstantIC
    variable = 'u'
    value = 3
    block = 3
  []
[]

[MeshModifiers]
  [moving_circle_bottom]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_1'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    reinitialize_subdomains = ''
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [moving_circle_top]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_2'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 2
    reinitialize_subdomains = ''
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[AuxVariables]
  [phi_1]
  []
  [phi_2]
  []
[]

[AuxKernels]
  [phi_1]
    type = ParsedAux
    variable = 'phi_1'
    expression = '(x-t)^2+(y)^2-0.3^2'
    use_xyzt = true
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [phi_2]
    type = ParsedAux
    variable = 'phi_2'
    expression = '(x-t)^2+(y-1)^2-0.3^2'
    use_xyzt = true
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[Executioner]
  type = Transient
  dt = 0.3
  num_steps = 3
[]

[Outputs]
  exodus = true
[]

(moose/test/tests/meshmodifiers/element_subdomain_modifier/reinitialization_from_into.i)

[Problem]
  kernel_coverage_check = false
[]

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    xmax = 1
    ymax = 1
    nx = 25
    ny = 25
  []
  [left]
    type = SubdomainBoundingBoxGenerator
    input = 'gen'
    block_id = 1
    bottom_left = '0 0 0'
    top_right = '0.3 1 0'
  []
  [middle]
    type = SubdomainBoundingBoxGenerator
    input = 'left'
    block_id = 2
    bottom_left = '0.3 0 0'
    top_right = '0.6 1 0'
  []
  [right]
    type = SubdomainBoundingBoxGenerator
    input = 'middle'
    block_id = 3
    bottom_left = '0.6 0 0'
    top_right = '1 1 0'
  []
[]

[Variables]
  [u]
  []
[]

[ICs]
  [u_1]
    type = ConstantIC
    variable = 'u'
    value = 1
    block = 1
  []
  [u_2]
    type = ConstantIC
    variable = 'u'
    value = 2
    block = 2
  []
  [u_3]
    type = ConstantIC
    variable = 'u'
    value = 3
    block = 3
  []
[]

[MeshModifiers]
  [moving_circle_bottom]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_1'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 1
    reinitialize_subdomains = '1 2'
    old_subdomain_reinitialized = false
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [moving_circle_top]
    type = CoupledVarThresholdElementSubdomainModifier
    coupled_var = 'phi_2'
    criterion_type = 'BELOW'
    threshold = 0
    subdomain_id = 2
    reinitialize_subdomains = '1 2'
    old_subdomain_reinitialized = false
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[AuxVariables]
  [phi_1]
  []
  [phi_2]
  []
[]

[AuxKernels]
  [phi_1]
    type = ParsedAux
    variable = 'phi_1'
    expression = '(x-t)^2+(y)^2-0.3^2'
    use_xyzt = true
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
  [phi_2]
    type = ParsedAux
    variable = 'phi_2'
    expression = '(x-t)^2+(y-1)^2-0.3^2'
    use_xyzt = true
    execute_on = 'INITIAL TIMESTEP_BEGIN'
  []
[]

[Executioner]
  type = Transient
  dt = 0.3
  num_steps = 3
[]

[Outputs]
  exodus = true
[]

Overview
Moving boundary / interface nodeset / sideset modification
Solution reinitialization
Stateful material property reinitialization
Reinitialization restrictions