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. Also, scalar variables that are constant in space but evolve in time can be described by ordinary differential equations.

Documentation on the major classes of variables are presented in:

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'
  []
[]
(examples/ex02_kernel/ex02.i)

Input Parameters

  • active__all__ If specified only the blocks named will be visited and made active

    Default:__all__

    C++ Type:std::vector<std::string>

    Controllable:No

    Description:If specified only the blocks named will be visited and made active

  • 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.

  • 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, MONOMIAL_VEC, RAVIART_THOMAS, RATIONAL_BERNSTEIN, SIDE_HIERARCHIC

    Controllable:No

    Description:Specifies the family of FE shape functions to use for this variable

  • inactiveIf specified blocks matching these identifiers will be skipped.

    C++ Type:std::vector<std::string>

    Controllable:No

    Description:If specified blocks matching these identifiers will be skipped.

  • initial_conditionSpecifies a constant initial condition for this variable

    C++ Type:std::vector<double>

    Controllable:No

    Description:Specifies a constant initial condition for this variable

  • 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

    Controllable:No

    Description:Specifies the order of the FE shape function to use for this variable (additional orders not listed are allowed)

  • scalingSpecifies a scaling factor to apply to this variable

    C++ Type:std::vector<double>

    Controllable:No

    Description:Specifies a scaling factor to apply to this variable

Optional Parameters

  • isObjectActionTrueIndicates that this is a MooseObjectAction.

    Default:True

    C++ Type:bool

    Controllable:No

    Description:Indicates that this is a MooseObjectAction.

Advanced Parameters

Available Objects

Available Actions