MultiAppUserObjectTransfer

Samples a variable's value in the Master domain at the point where the MultiApp is and copies that value into a post-processor in the MultiApp

Description

MultiAppUserObjectTransfer transfers information from a UserObject in the master/sub application to an AuxVariable in the sub/master application based on the direction of transfer (to_multiapp/from_multiApp).

The transfer can be restricted to a subdomain using the "block" parameter or a boundary using the "boundary" parameter.

To MultiApp

If the AuxVariable in the sub applications is a nodal AuxVariable, for each node in the sub application the value at the corresponding position in the master application is queried from the master UserObject, and this value is set to the AuxVariable at that node. A similar approach is followed for the elemental AuxVariable but with the centroid of the element instead of nodal position.

From MultiApp

For nodal AuxVariable in the master application, it is first determined whether the node is contained within the bounding box of the sub application. If the master node lies within a sub application's bounding box, the value of the sub application UserObject at that location is transferred to the master AuxVariable. A similar approach is followed for the elemental AuxVariable but with the centroid of the master element instead of nodal position.

When all_master_nodes_contained_in_sub_app option is set to true, an error is generated if the master node/element does not lie within the bounding boxes of any of the sub applications. An error is also generated if the master node/element lies within the bounding boxes of 2 or more sub applications.

Input Parameters

directionWhether this Transfer will be 'to' or 'from' a MultiApp, or bidirectional, by providing both FROM_MULTIAPP and TO_MULTIAPP.
C++ Type:MultiMooseEnum
Options:to_multiapp, from_multiapp
Description:Whether this Transfer will be 'to' or 'from' a MultiApp, or bidirectional, by providing both FROM_MULTIAPP and TO_MULTIAPP.
multi_appThe name of the MultiApp to use.
C++ Type:MultiAppName
Options:
Description:The name of the MultiApp to use.
user_objectThe UserObject you want to transfer values from. Note: This might be a UserObject from your MultiApp's input file!
C++ Type:UserObjectName
Options:
Description:The UserObject you want to transfer values from. Note: This might be a UserObject from your MultiApp's input file!
variableThe auxiliary variable to store the transferred values in.
C++ Type:std::vector<AuxVariableName>
Options:
Description:The auxiliary variable to store the transferred values in.

Required Parameters

all_master_nodes_contained_in_sub_appFalseSet to true if every master node is mapped to a distinct point on one of the subApps during a transfer from sub App to Master App. If master node cannot be found within bounding boxes of any of the subApps, an error is generated.
Default:False
C++ Type:bool
Options:
Description:Set to true if every master node is mapped to a distinct point on one of the subApps during a transfer from sub App to Master App. If master node cannot be found within bounding boxes of any of the subApps, an error is generated.
allow_skipped_adjustmentFalseIf set to true, the transfer skips adjustment when from or to postprocessor values are either zero or have different signs. If set to false, an error is thrown when encountering these conditions.
Default:False
C++ Type:bool
Options:
Description:If set to true, the transfer skips adjustment when from or to postprocessor values are either zero or have different signs. If set to false, an error is thrown when encountering these conditions.
blockThe block we are transferring to (if not specified, whole domain is used).
C++ Type:std::vector<SubdomainName>
Options:
Description:The block we are transferring to (if not specified, whole domain is used).
boundaryThe boundary we are transferring to (if not specified, whole domain is used unless 'block' parameter is used).
C++ Type:std::vector<BoundaryName>
Options:
Description:The boundary we are transferring to (if not specified, whole domain is used unless 'block' parameter is used).
check_multiapp_execute_onTrueWhen false the check between the multiapp and transfer execute on flags is not preformed.
Default:True
C++ Type:bool
Options:
Description:When false the check between the multiapp and transfer execute on flags is not preformed.
displaced_source_meshFalseWhether or not to use the displaced mesh for the source mesh.
Default:False
C++ Type:bool
Options:
Description:Whether or not to use the displaced mesh for the source mesh.
displaced_target_meshFalseWhether or not to use the displaced mesh for the target mesh.
Default:False
C++ Type:bool
Options:
Description:Whether or not to use the displaced mesh for the target mesh.
execute_onSAME_AS_MULTIAPPThe list of flag(s) indicating when this object should be executed, the available options include NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, FINAL, CUSTOM, SAME_AS_MULTIAPP.
Default:SAME_AS_MULTIAPP
C++ Type:ExecFlagEnum
Options:NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, FINAL, CUSTOM, SAME_AS_MULTIAPP
Description:The list of flag(s) indicating when this object should be executed, the available options include NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, FINAL, CUSTOM, SAME_AS_MULTIAPP.
from_postprocessors_to_be_preservedThe name of the Postprocessor in the from-app to evaluate an adjusting factor.
C++ Type:std::vector<PostprocessorName>
Options:
Description:The name of the Postprocessor in the from-app to evaluate an adjusting factor.
from_solution_tagThe tag of the solution vector to be transferred (default to the solution)
C++ Type:TagName
Options:
Description:The tag of the solution vector to be transferred (default to the solution)
skip_bounding_box_checkFalseSkip the check if the to_elem is within the bounding box of the from_app.
Default:False
C++ Type:bool
Options:
Description:Skip the check if the to_elem is within the bounding box of the from_app.
to_postprocessors_to_be_preservedThe name of the Postprocessor in the to-app to evaluate an adjusting factor.
C++ Type:std::vector<PostprocessorName>
Options:
Description:The name of the Postprocessor in the to-app to evaluate an adjusting factor.
to_solution_tagThe tag of the solution vector to be transferred to (default to the solution)
C++ Type:TagName
Options:
Description:The tag of the solution vector to be transferred to (default to the solution)

Optional Parameters

control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Options:
Description:Adds user-defined labels for accessing object parameters via control logic.
enableTrueSet the enabled status of the MooseObject.
Default:True
C++ Type:bool
Options:
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
Options:
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

Input Files

(test/tests/transfers/multiapp_userobject_transfer/tosub_displaced_master.i)
(modules/combined/test/tests/beam_eigenstrain_transfer/master_uo_transfer.i)
(test/tests/transfers/multiapp_conservative_transfer/master_userobject.i)
(test/tests/transfers/multiapp_high_order_variable_transfer/master_L2_Lagrange_userobject.i)
(test/tests/transfers/multiapp_userobject_transfer/restricted_elem_master.i)
(test/tests/transfers/multiapp_userobject_transfer/restricted_node_master.i)
(test/tests/transfers/multiapp_userobject_transfer/two_pipe_master.i)
(test/tests/transfers/multiapp_userobject_transfer/3d_1d_master.i)
(test/tests/vectorpostprocessors/csv_reader/transfer/master.i)
(test/tests/userobjects/postprocessor_spatial_user_object/master.i)
(test/tests/transfers/multiapp_userobject_transfer/tosub_master.i)
(test/tests/transfers/transfer_interpolation/master.i)
(test/tests/transfers/multiapp_userobject_transfer/master.i)

References

(test/tests/transfers/multiapp_userobject_transfer/tosub_displaced_master.i)

[Mesh]
  type = GeneratedMesh
  dim = 3
  nx = 20
  ny = 20
  nz = 20
  # The MultiAppUserObjectTransfer object only works with ReplicatedMesh
  parallel_type = replicated
[]

[Variables]
  [./u]
  [../]
[]

[AuxVariables]
  [./layered_average_value]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[Kernels]
  [./diff]
    type = Diffusion
    variable = u
  [../]
[]

[AuxKernels]
  [./layered_aux]
    type = SpatialUserObjectAux
    variable = layered_average_value
    execute_on = timestep_end
    user_object = layered_average
  [../]
[]

[BCs]
  [./bottom]
    type = DirichletBC
    variable = u
    boundary = bottom
    value = 0
  [../]
  [./top]
    type = DirichletBC
    variable = u
    boundary = top
    value = 1
  [../]
[]

[UserObjects]
  [./layered_average]
    type = LayeredAverage
    variable = u
    direction = y
    num_layers = 4
  [../]
[]

[Executioner]
  type = Transient
  num_steps = 1
  dt = 1

  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'
[]

[Outputs]
  exodus = true
[]

[MultiApps]
  [./sub_app]
    execute_on = timestep_end
    positions = '0 0 0'
    type = TransientMultiApp
    input_files = tosub_displaced_sub.i
    app_type = MooseTestApp
  [../]
[]

[Transfers]
  [./layered_transfer]
    direction = to_multiapp
    user_object = layered_average
    variable = multi_layered_average
    type = MultiAppUserObjectTransfer
    multi_app = sub_app
    displaced_target_mesh = true
  [../]
  [./element_layered_transfer]
    direction = to_multiapp
    user_object = layered_average
    variable = element_multi_layered_average
    type = MultiAppUserObjectTransfer
    multi_app = sub_app
    displaced_target_mesh = true
  [../]
[]

(modules/combined/test/tests/beam_eigenstrain_transfer/master_uo_transfer.i)

# Test for multi app vector postprocessor to aux variable transfer

# Master App contains 2 beams, one starting at (1.5, 2.0, 2.0) and
# another starting at (2.5, 0.0, 3.0). Both beams extend for
# 0.150080 m along the y direction.

# Each subApp contains a 2D model of width 0.5 m and height 0.150080 m.
# A time varying temperature profile is assigned to each 2D model and
# the resulting yy strain along the right boundary (x = 0.5) is
# transferred to the beam model using the multi app transfer. The subApps
# are positioned in the [MultiApp] block such that the origin of the beams
# coincides with the origin of the subApp.

# For each master beam node/element, the MultiAppUserObjectTransfer finds
# the subApp where this node belongs, projects this node to the right
# boundary of the subApp and assigns the value corresponding to the
# projected point.

# Result: The y displacement of the beam should equal the y
# displacement along the right boundary of the 2D model.

[Mesh]
  type = FileMesh
  file = 2_beams_new.e
[]

[Variables]
  [./disp_x]
  [../]
  [./disp_y]
  [../]
  [./disp_z]
  [../]
  [./rot_x]
    order = FIRST
    family = LAGRANGE
  [../]
  [./rot_y]
    order = FIRST
    family = LAGRANGE
  [../]
  [./rot_z]
    order = FIRST
    family = LAGRANGE
  [../]
[]

[BCs]
  [./fixx1]
    type = DirichletBC
    variable = disp_x
    boundary = 1
    value = 0.0
  [../]
  [./fixy1]
    type = DirichletBC
    variable = disp_y
    boundary = 1
    value = 0.0
  [../]
  [./fixz1]
    type = DirichletBC
    variable = disp_z
    boundary = 1
    value = 0.0
  [../]
  [./fixr1]
    type = DirichletBC
    variable = rot_x
    boundary = 1
    value = 0.0
  [../]
  [./fixr2]
    type = DirichletBC
    variable = rot_y
    boundary = 1
    value = 0.0
  [../]
  [./fixr3]
    type = DirichletBC
    variable = rot_z
    boundary = 1
    value = 0.0
  [../]
[]

[Kernels]
  [./solid_disp_x]
    type = StressDivergenceBeam
    block = '1'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 0
    variable = disp_x
  [../]
  [./solid_disp_y]
    type = StressDivergenceBeam
    block = '1'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 1
    variable = disp_y
  [../]
  [./solid_disp_z]
    type = StressDivergenceBeam
    block = '1'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 2
    variable = disp_z
  [../]
  [./solid_rot_x]
    type = StressDivergenceBeam
    block = '1'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 3
    variable = rot_x
  [../]
  [./solid_rot_y]
    type = StressDivergenceBeam
    block = '1'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 4
    variable = rot_y
  [../]
  [./solid_rot_z]
    type = StressDivergenceBeam
    block = '1'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 5
    variable = rot_z
  [../]
[]

[Materials]
  [./elasticity]
    type = ComputeElasticityBeam
    youngs_modulus = 1e9
    poissons_ratio = 0.3
    shear_coefficient = 1.0
    block = 1
  [../]
  [./strain]
    type = ComputeIncrementalBeamStrain
    block = '1'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    area = 0.5
    Ay = 0.0
    Az = 0.0
    Iy = 0.01
    Iz = 0.01
    y_orientation = '0.0 0.0 1.0'
    eigenstrain_names = 'thermal'
  [../]
  [./stress]
    type = ComputeBeamResultants
    block = 1
  [../]
  [./thermal]
    type = ComputeEigenstrainBeamFromVariable
    displacement_eigenstrain_variables = 'zero1 to_var zero2'
    eigenstrain_name = thermal
  [../]
[]

[Executioner]
  type = Transient

  #Preconditioned JFNK (default)
  solve_type = 'PJFNK'

  line_search = 'none'

  l_max_its = 50
  nl_max_its = 50
  nl_rel_tol = 1e-12
  nl_abs_tol = 1e-12
  l_tol = 1e-9

  start_time = 0.0
  end_time = 0.075
  dt = 0.0125
  dtmin = 0.0001
[]

[AuxVariables]
  [./to_var]
  [../]
  [./zero1]
  [../]
  [./zero2]
  [../]
[]

[MultiApps]
  [./sub]
    type = TransientMultiApp
    app_type = CombinedApp
    positions = '1.5 2.0 2.0 2.5 0.0 3.0'
    input_files = 'subapp1_uo_transfer.i subapp2_uo_transfer.i'
  [../]
[]

[Transfers]
  [./fromsub]
    type = MultiAppUserObjectTransfer
    direction = from_multiapp
    user_object = axial_str
    multi_app = sub
    variable = to_var
    all_master_nodes_contained_in_sub_app = true
  [../]
[]

[Postprocessors]
  [./pos1]
    type = PointValue
    variable = disp_y
    point = '1.5 2.150080 2.0'
  [../]
  [./pos2]
    type = PointValue
    variable = disp_y
    point = '2.5 0.150080 3.0'
  [../]
[]

[Outputs]
  exodus = true
[]

(test/tests/transfers/multiapp_conservative_transfer/master_userobject.i)

[Mesh]
  type = GeneratedMesh
  dim = 3
  nx = 20
  ny = 20
  nz = 20
  # The MultiAppUserObjectTransfer object only works with ReplicatedMesh
  parallel_type = replicated
[]

[Variables]
  [./u]
  [../]
[]

[AuxVariables]
  [./multi_layered_average]
  [../]
  [./element_multi_layered_average]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[Kernels]
  [./diff]
    type = Diffusion
    variable = u
  [../]
  [./td]
    type = TimeDerivative
    variable = u
  [../]
[]

[BCs]
  [./left]
    type = DirichletBC
    variable = u
    boundary = left
    value = 0
  [../]
  [./right]
    type = DirichletBC
    variable = u
    boundary = right
    value = 1
  [../]
[]

[Executioner]
  type = Transient
  num_steps = 1
  dt = 0.001 # This will be constrained by the multiapp

  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'
  l_tol = 1e-8
  nl_rel_tol = 1e-10
[]


[Outputs]
  exodus = true
  csv = true
[]

[VectorPostprocessors]
  [to_nearest_point]
    type = NearestPointIntegralVariablePostprocessor
    variable = multi_layered_average
    points = '0.3 0.1 0.3 0.7 0.1 0.3'
    execute_on = 'transfer'
  []

  [to_nearest_point_element]
    type = NearestPointIntegralVariablePostprocessor
    variable = element_multi_layered_average
    points = '0.3 0.1 0.3 0.7 0.1 0.3'
    execute_on = 'transfer'
  []
[]

[MultiApps]
  [./sub_app]
    positions = '0.3 0.1 0.3 0.7 0.1 0.3'
    type = TransientMultiApp
    input_files = sub_userobject.i
    app_type = MooseTestApp
  [../]
[]

[Transfers]
  [./layered_transfer]
    direction = from_multiapp
    user_object = layered_average
    variable = multi_layered_average
    type = MultiAppUserObjectTransfer
    multi_app = sub_app

    from_postprocessors_to_be_preserved  = 'from_postprocessor'
    to_postprocessors_to_be_preserved  = 'to_nearest_point'
  [../]
  [./element_layered_transfer]
    direction = from_multiapp
    user_object = layered_average
    variable = element_multi_layered_average
    type = MultiAppUserObjectTransfer
    multi_app = sub_app

    from_postprocessors_to_be_preserved  = 'from_postprocessor'
    to_postprocessors_to_be_preserved  = 'to_nearest_point_element'
  [../]
[]

(test/tests/transfers/multiapp_high_order_variable_transfer/master_L2_Lagrange_userobject.i)

[Mesh]
  type = GeneratedMesh
  dim = 2
  nx = 20
  ny = 20
  parallel_type = replicated
[]

[Variables]
  [power_density]
    family = L2_LAGRANGE
    order = FIRST
  []
[]

[AuxVariables]
  [./multi_layered_average]
    family = LAGRANGE
    order = FIRST
  [../]
[]

[UserObjects]
  [./multi_layered_average]
    type = LayeredAverage
    variable = power_density
    direction = y
    num_layers = 4
  [../]
[]

[AuxKernels]
  [./layered_aux]
    type = SpatialUserObjectAux
    variable = multi_layered_average
    execute_on = 'nonlinear TIMESTEP_END'
    user_object = multi_layered_average
  [../]
[]

[Functions]
  [pwr_func]
    type = ParsedFunction
    value = '1e3*x*(1-x)+5e2'
  []
[]

[Kernels]
  [diff]
    type = Reaction
    variable = power_density
  []

  [coupledforce]
    type = BodyForce
    variable = power_density
    function = pwr_func
  []
[]

[Postprocessors]
  [layered_avg]
    type = ElementAverageValue
    block = '0'
    variable = multi_layered_average
    execute_on = 'initial timestep_end'
  []
[]

[Executioner]
  type = Steady
  petsc_options_iname = '-pc_type -pc_hypre_type -ksp_gmres_restart '
  petsc_options_value = 'hypre boomeramg 100'

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

[MultiApps]
  [sub]
    type = FullSolveMultiApp
    app_type = MooseTestApp
    positions = '0 0 0'
    input_files  = sub_L2_Lagrange.i
    execute_on = 'timestep_end'
  []
[]

[Transfers]
  [p_to_sub]
    type = MultiAppUserObjectTransfer
    direction = to_multiapp
    user_object = multi_layered_average
    variable = power_density
    multi_app = sub
    execute_on = 'timestep_end'
  []
[]

[Outputs]
  exodus = true
  perf_graph = true
[]

(test/tests/transfers/multiapp_userobject_transfer/restricted_elem_master.i)

num_layers = 2

[Mesh]
  [box]
    type = GeneratedMeshGenerator
    dim = 3
    nx = ${num_layers}
    ny = 3
    nz = 3
  []
  # The MultiAppUserObjectTransfer object only works with ReplicatedMesh
  parallel_type = replicated
[]

[Variables]
  [u]
  []
[]

[Kernels]
  [td]
    type = TimeDerivative
    variable = u
  []

  [diff]
    type = Diffusion
    variable = u
  []
[]

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

  [s]
  []
[]

[AuxKernels]
  [s_ak]
    type = ParsedAux
    variable = s
    use_xyzt = true
    function = 'x+(z*z)'
  []
[]

[Functions]
[]

[Postprocessors]
  [a_avg]
    type = ElementAverageValue
    variable = a
  []
[]

[UserObjects]
  [S_avg_front]
    type = LayeredSideAverage
    boundary = front
    variable = s
    num_layers = ${num_layers}
    direction = x
  []

  [S_avg_back]
    type = LayeredSideAverage
    boundary = back
    variable = s
    num_layers = ${num_layers}
    direction = x
  []
[]

[MultiApps]
  [ch0]
    type = TransientMultiApp
    input_files = 'restricted_elem_sub.i'
    bounding_box_padding = '0 0.5 1'
    positions = '0 0.5 -0.1'
    output_in_position = true
    cli_args = 'yy=0'
  []
  [ch1]
    type = TransientMultiApp
    input_files = 'restricted_elem_sub.i'
    bounding_box_padding = '0 0.5 1'
    positions = '0 0.5  1.1'
    output_in_position = true
    cli_args = 'yy=1'
  []
[]

[Transfers]
  [from_ch0]
    type = MultiAppUserObjectTransfer
    boundary = back
    direction = from_multiapp
    multi_app = ch0
    variable = a
    user_object = A_avg
  []

  [from_ch1]
    type = MultiAppUserObjectTransfer
    boundary = front
    direction = from_multiapp
    multi_app = ch1
    variable = a
    user_object = A_avg
  []

  [to_ch0]
    type = MultiAppUserObjectTransfer
    block = 20
    direction = to_multiapp
    multi_app = ch0
    variable = S
    user_object = S_avg_back
  []

  [to_ch1]
    type = MultiAppUserObjectTransfer
    block = 20
    direction = to_multiapp
    multi_app = ch1
    variable = S
    user_object = S_avg_front
  []
[]

[Executioner]
  type = Transient
  num_steps = 2

  dt = 1
  nl_abs_tol = 1e-7
[]

[Outputs]
  exodus = true
[]

(test/tests/transfers/multiapp_userobject_transfer/restricted_node_master.i)

num_layers = 2

[Mesh]
  [box]
    type = GeneratedMeshGenerator
    dim = 3
    nx = ${num_layers}
    ny = 3
    nz = 3
    xmin = 0.25
    xmax = 1.25
  []
  # The MultiAppUserObjectTransfer object only works with ReplicatedMesh
  parallel_type = replicated
[]

[Variables]
  [u]
  []
[]

[Kernels]
  [td]
    type = TimeDerivative
    variable = u
  []

  [diff]
    type = Diffusion
    variable = u
  []
[]

[AuxVariables]
  [a]
  []

  [s]
  []
[]

[AuxKernels]
  [s_ak]
    type = ParsedAux
    variable = s
    use_xyzt = true
    function = 'x+(z*z)'
  []
[]

[Functions]
[]

[Postprocessors]
  [a_avg]
    type = ElementAverageValue
    variable = a
  []
[]

[UserObjects]
  [S_avg_front]
    type = LayeredSideAverage
    boundary = front
    variable = s
    num_layers = ${num_layers}
    direction = x
  []

  [S_avg_back]
    type = LayeredSideAverage
    boundary = back
    variable = s
    num_layers = ${num_layers}
    direction = x
  []
[]

[MultiApps]
  [ch0]
    type = TransientMultiApp
    input_files = 'restricted_node_sub.i'
    bounding_box_padding = '0 0.5 1'
    positions = '0 0.5 -0.1'
    output_in_position = true
    cli_args = 'yy=0'
  []
  [ch1]
    type = TransientMultiApp
    input_files = 'restricted_node_sub.i'
    bounding_box_padding = '0 0.5 1'
    positions = '0 0.5  1.1'
    output_in_position = true
    cli_args = 'yy=1'
  []
[]

[Transfers]
  [from_ch0]
    type = MultiAppUserObjectTransfer
    boundary = back
    direction = from_multiapp
    multi_app = ch0
    variable = a
    user_object = A_avg
  []

  [from_ch1]
    type = MultiAppUserObjectTransfer
    boundary = front
    direction = from_multiapp
    multi_app = ch1
    variable = a
    user_object = A_avg
  []

  [to_ch0]
    type = MultiAppUserObjectTransfer
    block = 20
    direction = to_multiapp
    multi_app = ch0
    variable = S
    user_object = S_avg_back
  []

  [to_ch1]
    type = MultiAppUserObjectTransfer
    block = 20
    direction = to_multiapp
    multi_app = ch1
    variable = S
    user_object = S_avg_front
  []
[]

[Executioner]
  type = Transient
  num_steps = 2

  dt = 1
  nl_abs_tol = 1e-7
[]

[Outputs]
  exodus = true
[]

(test/tests/transfers/multiapp_userobject_transfer/two_pipe_master.i)

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 3
    xmin = 0
    xmax = 5
    nx = 5

    ymin = 0
    ymax = 5
    ny = 5

    zmin = 0
    zmax = 5
    nz = 5
  []
  [./blocks]
    input = gen
    type = SubdomainBoundingBoxGenerator
    block_id = 1
    bottom_left = '1 1 0'
    top_right = '4 4 5'
  [../]
[]

[AuxVariables]
  [./from_sub_app_var]
    order = CONSTANT
    family = MONOMIAL
    block = 1
    initial_condition = 0
  [../]
[]

[Variables]
  [u]
  []
[]

[Kernels]
  [diff]
    type = Diffusion
    variable = u
  []
  [td]
    type = TimeDerivative
    variable = u
  []
[]

[BCs]
  [left]
    type = DirichletBC
    variable = u
    boundary = front
    value = -1
  []
  [right]
    type = DirichletBC
    variable = u
    boundary = back
    value = 1
  []
[]

[Executioner]
  type = Transient
  num_steps = 2
  dt = 5

  solve_type = 'NEWTON'
  l_tol = 1e-8
  nl_rel_tol = 1e-10
[]

[Outputs]
  exodus = true
  execute_on = final
[]

[MultiApps]
  [sub_app]
    type = TransientMultiApp
    positions = '0 0 0'
    input_files = two_pipe_sub.i
    app_type = MooseTestApp
    execute_on = TIMESTEP_END
  []
[]

[Transfers]
  [layered_transfer_from_sub_app]
    type = MultiAppUserObjectTransfer
    direction = from_multiapp
    user_object = sub_app_uo
    variable = from_sub_app_var
    multi_app = sub_app
    displaced_source_mesh = true
    skip_bounding_box_check = true
  []
[]

(test/tests/transfers/multiapp_userobject_transfer/3d_1d_master.i)

# This does a dummy diffusion solve in 3D space, then computes a layered average
# in the z direction. Those values are transferred into a sub-app that has 1D mesh
# in the z-direction (the mesh was displaced so that it is aligned in such a way).
# The sub-app also does a dummy diffusion solve and then computes layered average
# in the z-direction. Those value are transferred back to the master app.
#
# Physically the 1D sub-app is placed in the center of the 3D mesh and is oriented
# in the z-direction.  The bounding box of the sub-app is expanded such that it
# contains the 4 central elements of the 3D mesh (i.e. the values are transferred
# only into a part of master mesh)

[Mesh]
  type = GeneratedMesh
  dim = 3
  nx = 4
  ny = 4
  nz = 10
  # The MultiAppUserObjectTransfer object only works with ReplicatedMesh
  parallel_type = replicated
[]

[AuxVariables]
  [./from_sub_app_var]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[UserObjects]
  [master_uo]
    type = LayeredAverage
    direction = z
    num_layers = 10
    variable = u
  []
[]

[Variables]
  [u]
  []
[]

[Kernels]
  [diff]
    type = Diffusion
    variable = u
  []
  [td]
    type = TimeDerivative
    variable = u
  []
[]

[BCs]
  [left]
    type = DirichletBC
    variable = u
    boundary = front
    value = -1
  []
  [right]
    type = DirichletBC
    variable = u
    boundary = back
    value = 1
  []
[]

[Executioner]
  type = Transient
  num_steps = 2
  dt = 5

  solve_type = 'NEWTON'
  l_tol = 1e-8
  nl_rel_tol = 1e-10
[]

[Outputs]
  exodus = true
  execute_on = final
[]

[MultiApps]
  [sub_app]
    positions = '0.5 0.5 0.0'
    type = TransientMultiApp
    input_files = 3d_1d_sub.i
    app_type = MooseTestApp
    bounding_box_padding = '0.25 0.25 0'
    bounding_box_inflation = 0
    use_displaced_mesh = true
    execute_on = TIMESTEP_END
  []
[]

[Transfers]
  [layered_transfer_to_sub_app]
    type = MultiAppUserObjectTransfer
    direction = to_multiapp
    user_object = master_uo
    variable = sub_app_var
    multi_app = sub_app
    displaced_target_mesh = true
  []
  [layered_transfer_from_sub_app]
    type = MultiAppUserObjectTransfer
    direction = from_multiapp
    user_object = sub_app_uo
    variable = from_sub_app_var
    multi_app = sub_app
    displaced_source_mesh = true
  []
[]

(test/tests/vectorpostprocessors/csv_reader/transfer/master.i)

[Mesh]
  type = GeneratedMesh
  parallel_type = 'replicated'
  dim = 2
  nx = 10
  ny = 10
[]

[Variables]
  [./u]
  [../]
[]

[Kernels]
  [./diff]
    type = Diffusion
    variable = u
  [../]
[]

[BCs]
  [./left]
    type = DirichletBC
    variable = u
    boundary = left
    value = 0
  [../]
  [./right]
    type = DirichletBC
    variable = u
    boundary = right
    value = 1
  [../]
[]

[MultiApps]
  [./master]
    type = FullSolveMultiApp
    input_files = 'sub.i'
    execute_on = initial
  [../]
[]

[Transfers]
  [./transfer]
    type = MultiAppUserObjectTransfer
    multi_app = master
    direction = to_multiapp
    user_object = data
    variable = aux
  [../]
[]

[VectorPostprocessors]
  [./data]
    type = CSVReader
    csv_file = 'example.csv'
  [../]
[]


[Executioner]
  type = Steady
  solve_type = 'PJFNK'
  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'
[]

[Outputs]
  exodus = true
[]

(test/tests/userobjects/postprocessor_spatial_user_object/master.i)

[Mesh]
  type = GeneratedMesh
  dim = 2
  nx = 4
  ny = 4
[]

[Functions]
  [./ic_fn]
    type = ParsedFunction
    value = 'x * y'
  [../]
[]

[Variables]
  [./u]
    family = LAGRANGE
    order = FIRST
  [../]
[]

[ICs]
  [./u_ic]
    type = FunctionIC
    variable = u
    function = ic_fn
  [../]

  [./a_ic]
    type = ConstantIC
    variable = a
    value = 1
  [../]
[]

[AuxVariables]
  [./a]
  [../]
[]

[Kernels]
  [./td]
    type = TimeDerivative
    variable = u
  [../]
  [./rhs]
    type = BodyForce
    variable = u
    function = 1
  [../]
[]

[MultiApps]
  [./sub]
    type = TransientMultiApp
    app_type = MooseTestApp
    input_files = 'sub.i'
    positions = '
      0.25 0.25 0
      0.75 0.75 0'
    execute_on = 'initial timestep_end'
  [../]
[]

[Transfers]
  [./master_to_sub]
    type = MultiAppNearestNodeTransfer
    direction = to_multiapp
    multi_app = sub
    source_variable = u
    variable = a
  [../]

  [./sub_to_master]
    type = MultiAppUserObjectTransfer
    direction = from_multiapp
    multi_app = sub
    user_object = fn_uo
    variable = a
  [../]
[]

[Executioner]
  type = Transient
  dt = 0.1
  num_steps = 10
[]

[Outputs]
  exodus = true
[]

(test/tests/transfers/multiapp_userobject_transfer/tosub_master.i)

[Mesh]
  type = GeneratedMesh
  dim = 3
  nx = 20
  ny = 20
  nz = 20
  # The MultiAppUserObjectTransfer object only works with ReplicatedMesh
  parallel_type = replicated
[]

[Variables]
  [./u]
  [../]
[]

[AuxVariables]
  [./layered_average_value]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[Kernels]
  [./diff]
    type = Diffusion
    variable = u
  [../]
[]

[AuxKernels]
  [./layered_aux]
    type = SpatialUserObjectAux
    variable = layered_average_value
    execute_on = timestep_end
    user_object = layered_average
  [../]
[]

[BCs]
  [./bottom]
    type = DirichletBC
    variable = u
    boundary = bottom
    value = 0
  [../]
  [./top]
    type = DirichletBC
    variable = u
    boundary = top
    value = 1
  [../]
[]

[UserObjects]
  [./layered_average]
    type = LayeredAverage
    variable = u
    direction = y
    num_layers = 4
  [../]
[]

[Executioner]
  type = Transient
  num_steps = 1
  dt = 1

  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'
[]

[Outputs]
  exodus = true
[]

[MultiApps]
  [./sub_app]
    execute_on = timestep_end
    positions = '0.3 0.1 0.3 0.7 0.1 0.3'
    type = TransientMultiApp
    input_files = tosub_sub.i
    app_type = MooseTestApp
  [../]
[]

[Transfers]
  [./layered_transfer]
    direction = to_multiapp
    user_object = layered_average
    variable = multi_layered_average
    type = MultiAppUserObjectTransfer
    multi_app = sub_app
  [../]
  [./element_layered_transfer]
    direction = to_multiapp
    user_object = layered_average
    variable = element_multi_layered_average
    type = MultiAppUserObjectTransfer
    multi_app = sub_app
  [../]
[]

(test/tests/transfers/transfer_interpolation/master.i)

[Mesh]
  type = GeneratedMesh
  dim = 2
  nx = 10
  ny = 10
  # This test currently diffs when run in parallel with DistributedMesh enabled,
  # most likely due to the fact that it uses some geometric search stuff.
  # For more information, see #2121.
  parallel_type = replicated
[]

[Variables]
  [./u]
  [../]
[]

[Kernels]
  [./diff]
    type = Diffusion
    variable = u
  [../]
[]

[BCs]
  [./left]
    type = DirichletBC
    variable = u
    boundary = left
    value = 0
  [../]
  [./right]
    type = DirichletBC
    variable = u
    boundary = right
    value = 1
  [../]
[]

[UserObjects]
  [./layered_average]
    type = LayeredAverage
    variable = u
    direction = x
    num_layers = 3
  [../]
[]

[Executioner]
  type = Transient
  num_steps = 1
  dt = 1
  nl_rel_tol = 1e-10

  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'
[]

[Outputs]
  exodus = true
[]
[MultiApps]
  [./sub]
    type = TransientMultiApp
    app_type = MooseTestApp
    execute_on = timestep_end
    positions = '0 0 0'
    input_files = sub.i
    sub_cycling = true
    interpolate_transfers = true
    output_sub_cycles = true
  [../]
[]

[Transfers]
  [./nearest_node]
    type = MultiAppNearestNodeTransfer
    direction = to_multiapp
    multi_app = sub
    source_variable = u
    variable = nearest_node
  [../]
  [./mesh_function]
    type = MultiAppMeshFunctionTransfer
    direction = to_multiapp
    multi_app = sub
    source_variable = u
    variable = mesh_function
  [../]
  [./user_object]
    type = MultiAppUserObjectTransfer
    direction = to_multiapp
    multi_app = sub
    variable = user_object
    user_object = layered_average
  [../]
  [./interpolation]
    type = MultiAppInterpolationTransfer
    direction = to_multiapp
    multi_app = sub
    source_variable = u
    variable = interpolation
  [../]
[]

(test/tests/transfers/multiapp_userobject_transfer/master.i)

[Mesh]
  type = GeneratedMesh
  dim = 3
  nx = 20
  ny = 20
  nz = 20
  # The MultiAppUserObjectTransfer object only works with ReplicatedMesh
  parallel_type = replicated
[]

[Variables]
  [./u]
  [../]
[]

[AuxVariables]
  [./multi_layered_average]
  [../]
  [./element_multi_layered_average]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[Kernels]
  [./diff]
    type = Diffusion
    variable = u
  [../]
  [./td]
    type = TimeDerivative
    variable = u
  [../]
[]

[BCs]
  [./left]
    type = DirichletBC
    variable = u
    boundary = left
    value = 0
  [../]
  [./right]
    type = DirichletBC
    variable = u
    boundary = right
    value = 1
  [../]
[]

[Executioner]
  type = Transient
  num_steps = 1
  dt = 0.001 # This will be constrained by the multiapp

  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'
  l_tol = 1e-8
  nl_rel_tol = 1e-10
[]


[Outputs]
  exodus = true
[]

[MultiApps]
  [./sub_app]
    positions = '0.3 0.1 0.3 0.7 0.1 0.3'
    type = TransientMultiApp
    input_files = sub.i
    app_type = MooseTestApp
  [../]
[]

[Transfers]
  [./layered_transfer]
    direction = from_multiapp
    user_object = layered_average
    variable = multi_layered_average
    type = MultiAppUserObjectTransfer
    multi_app = sub_app
  [../]
  [./element_layered_transfer]
    direction = from_multiapp
    user_object = layered_average
    variable = element_multi_layered_average
    type = MultiAppUserObjectTransfer
    multi_app = sub_app
  [../]
[]

Description
To MultiApp
From MultiApp
Input Parameters
Input Files
References

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