ConstantFunction

A function that returns a constant value as defined by an input parameter.

The value parameter of the ConstantFunction is controllable, so it may modified during the simulation using the Controls system.

Example input syntax

This example uses a ConstantFunction to feed into vectorized spatial samplers, which sample the function in specified locations. These samples are then compared using another postprocessor. The ConstantFunction sampled anywhere in time and space will return its constant value.

[Functions<<<{"href": "../../syntax/Functions/index.html"}>>>]
  # Sampled values will be [2, 2, 2]
  [./a_fn]
    type = ConstantFunction<<<{"description": "A function that returns a constant value as defined by an input parameter.", "href": "ConstantFunction.html"}>>>
    value<<<{"description": "The constant value"}>>> = 2
  [../]
  # Sampled values will be [0, 1, 2]
  [./b_fn]
    type = ParsedFunction<<<{"description": "Function created by parsing a string", "href": "MooseParsedFunction.html"}>>>
    expression<<<{"description": "The user defined function."}>>> = 'x'
  [../]
[]

Input Parameters

value0The constant value
Default:0
C++ Type:double
Unit:(no unit assumed)
Controllable:Yes
Description:The constant value

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:No
Description:Set the enabled status of the MooseObject.

Advanced Parameters

(moose/test/tests/postprocessors/vector_postprocessor_comparison/vector_postprocessor_comparison.i)

# This tests the VectorPostprocessorComparison post-processor, which takes two
# vector post-processors and compares them.

[Mesh]
  type = GeneratedMesh
  dim = 1
  nx = 3
  xmin = 0
  xmax = 2
[]

[Functions]
  # Sampled values will be [2, 2, 2]
  [./a_fn]
    type = ConstantFunction
    value = 2
  [../]
  # Sampled values will be [0, 1, 2]
  [./b_fn]
    type = ParsedFunction
    expression = 'x'
  [../]
[]

[VectorPostprocessors]
  [./a_vpp]
    type = LineFunctionSampler
    functions = 'a_fn'
    num_points = 3
    start_point = '0 0 0'
    end_point = '2 0 0'
    sort_by = x
    execute_on = 'initial'
  [../]
  [./b_vpp]
    type = LineFunctionSampler
    functions = 'b_fn'
    num_points = 3
    start_point = '0 0 0'
    end_point = '2 0 0'
    sort_by = x
    execute_on = 'initial'
  [../]
[]

[Postprocessors]
  [./vpp_comparison]
    type = VectorPostprocessorComparison
    vectorpostprocessor_a = a_vpp
    vectorpostprocessor_b = b_vpp
    vector_name_a = a_fn
    vector_name_b = b_fn
    comparison_type = greater_than_equals
    execute_on = 'initial'
  [../]
[]

[Problem]
  solve = false
[]

[Executioner]
  type = Steady
[]

[Outputs]
  file_base = greater_than_equals
  csv = true
  show = 'vpp_comparison'
  execute_on = 'initial'
[]

Example input syntax
Input Parameters