Variables System

Description

The Variables block within an input file is utilized to define the unknowns within a system of partial differential equations. These unknowns are often referred to as nonlinear variables within documentation. The nonlinear variables defined within this block are used by Kernel objects to define the equations for a simulation.

Example

The following input file snippet demonstrates the creation of a single nonlinear variable that is used by two Kernel objects, refer to Example 2 for more details.

[Variables]
  [convected]
    order = FIRST
    family = LAGRANGE
  []
[]

[Kernels]
  [diff]
    type = Diffusion
    variable = convected
  []

  [conv]
    type = ExampleConvection
    variable = convected
    velocity = '0.0 0.0 1.0'
  []
[]

/opt/civet/build_0/moose/examples/ex02_kernel/ex02.i

[Mesh]
  file = mug.e
[]

[Variables]
  [convected]
    order = FIRST
    family = LAGRANGE
  []
[]

[Kernels]
  [diff]
    type = Diffusion
    variable = convected
  []

  [conv]
    type = ExampleConvection
    variable = convected
    velocity = '0.0 0.0 1.0'
  []
[]

[BCs]
  [bottom]
    type = DirichletBC
    variable = convected
    boundary = 'bottom'
    value = 1
  []

  [top]
    type = DirichletBC
    variable = convected
    boundary = 'top'
    value = 0
  []
[]

[Executioner]
  type = Steady
  solve_type = 'PJFNK'
[]

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

Input Parameters

familyLAGRANGESpecifies the family of FE shape functions to use for this variable
Default:LAGRANGE
C++ Type:MooseEnum
Options:LAGRANGE MONOMIAL HERMITE SCALAR HIERARCHIC CLOUGH XYZ SZABAB BERNSTEIN L2_LAGRANGE L2_HIERARCHIC NEDELEC_ONE LAGRANGE_VEC
Description:Specifies the family of FE shape functions to use for this variable
initial_conditionSpecifies the initial condition for this variable
C++ Type:double
Options:
Description:Specifies the initial condition for this variable
inactiveIf specified blocks matching these identifiers will be skipped.
C++ Type:std::vector
Options:
Description:If specified blocks matching these identifiers will be skipped.
active__all__ If specified only the blocks named will be visited and made active
Default:__all__
C++ Type:std::vector
Options:
Description:If specified only the blocks named will be visited and made active
orderFIRSTSpecifies the order of the FE shape function to use for this variable (additional orders not listed are allowed)
Default:FIRST
C++ Type:MooseEnum
Options:CONSTANT FIRST SECOND THIRD FOURTH
Description:Specifies the order of the FE shape function to use for this variable (additional orders not listed are allowed)
blockThe block id where this variable lives
C++ Type:std::vector
Options:
Description:The block id where this variable lives

Optional Parameters

scaling1Specifies a scaling factor to apply to this variable
Default:1
C++ Type:double
Options:
Description:Specifies a scaling factor to apply to this variable
outputsVector of output names were you would like to restrict the output of variables(s) associated with this object
C++ Type:std::vector
Options:
Description:Vector of output names were you would like to restrict the output of variables(s) associated with this object
eigenFalseTrue to make this variable an eigen variable
Default:False
C++ Type:bool
Options:
Description:True to make this variable an eigen variable

Advanced Parameters

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