ODETimeDerivative

Returns the time derivative contribution to the residual for a scalar variable.

A scalar variable can be set to the solution of an ordinary differential equation (ODE), as specified in the Scalar Kernels syntax page. This kernel adds a time derivative term. The time integration scheme will be shared with the other non-linear variables. To use a different time integrating scheme, the ODETimeDerivative scalar kernel should be replaced with a custom implementation.

Example input syntax

In this example, the scalar variables x and y are the solutions to the coupled ODE problem:

var element = document.getElementById("moose-equation-48e4493c-d342-44c9-a854-e9929475c162");katex.render("\\dfrac{d x}{d t} -3*x - 2*y = 0", element, {displayMode:true,throwOnError:false});

var element = document.getElementById("moose-equation-80e206ec-3285-4ac1-afe4-27e8138dcae0");katex.render("\\dfrac{d y}{d t} -4*x - y = 0", element, {displayMode:true,throwOnError:false});

The time derivative terms are added for each variable using two ODETimeDerivative scalar kernels.

[ScalarKernels]
  [./td1]
    type = ODETimeDerivative
    variable = x
  [../]
  [./ode1]
    type = ParsedODEKernel
    expression = '-3*x - 2*y'
    variable = x
    coupled_variables = y
  [../]

  [./td2]
    type = ODETimeDerivative
    variable = y
  [../]
  [./ode2]
    type = ParsedODEKernel
    expression = '-4*x - y'
    variable = y
    coupled_variables = x
  [../]
[]

Input Parameters

variableThe name of the variable that this residual object operates on
C++ Type:NonlinearVariableName
Unit:(no unit assumed)
Controllable:No
Description:The name of the variable that this residual object operates on

Required Parameters

absolute_value_vector_tagsThe tags for the vectors this residual object should fill with the absolute value of the residual contribution
C++ Type:std::vector<TagName>
Unit:(no unit assumed)
Controllable:No
Description:The tags for the vectors this residual object should fill with the absolute value of the residual contribution
extra_matrix_tagsThe extra tags for the matrices this Kernel should fill
C++ Type:std::vector<TagName>
Unit:(no unit assumed)
Controllable:No
Description:The extra tags for the matrices this Kernel should fill
extra_vector_tagsThe extra tags for the vectors this Kernel should fill
C++ Type:std::vector<TagName>
Unit:(no unit assumed)
Controllable:No
Description:The extra tags for the vectors this Kernel should fill
matrix_tagssystem timeThe tag for the matrices this Kernel should fill
Default:system time
C++ Type:MultiMooseEnum
Unit:(no unit assumed)
Options:nontime, system, time
Controllable:No
Description:The tag for the matrices this Kernel should fill
vector_tagstimeThe tag for the vectors this Kernel should fill
Default:time
C++ Type:MultiMooseEnum
Unit:(no unit assumed)
Options:nontime, time
Controllable:No
Description:The tag for the vectors this Kernel should fill

Tagging Parameters

control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
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
Unit:(no unit assumed)
Controllable:Yes
Description:Set the enabled status of the MooseObject.
implicitTrueDetermines whether this object is calculated using an implicit or explicit form
Default:True
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Determines whether this object is calculated using an implicit or explicit form
seed0The seed for the master random number generator
Default:0
C++ Type:unsigned int
Unit:(no unit assumed)
Controllable:No
Description:The seed for the master random number generator
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
Unit:(no unit assumed)
Controllable:No
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

(moose/test/tests/kernels/ode/parsedode_sys_impl_test.i)

[Mesh]
  type = GeneratedMesh
  dim = 2
  xmin = 0
  xmax = 1
  ymin = 0
  ymax = 1
  nx = 2
  ny = 2
  elem_type = QUAD4
[]

[Functions]
  [./f_fn]
    type = ParsedFunction
    expression = -4
  [../]
  [./bc_all_fn]
    type = ParsedFunction
    expression = x*x+y*y
  [../]

  # ODEs
  [./exact_x_fn]
    type = ParsedFunction
    expression = (-1/3)*exp(-t)+(4/3)*exp(5*t)
  [../]
[]

# NL

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

  # ODE variables
  [./x]
    family = SCALAR
    order = FIRST
    initial_condition = 1
  [../]
  [./y]
    family = SCALAR
    order = FIRST
    initial_condition = 2
  [../]
[]

[Kernels]
  [./td]
    type = TimeDerivative
    variable = u
  [../]
  [./diff]
    type = Diffusion
    variable = u
  [../]
  [./uff]
    type = BodyForce
    variable = u
    function = f_fn
  [../]
[]

[ScalarKernels]
  [./td1]
    type = ODETimeDerivative
    variable = x
  [../]
  [./ode1]
    type = ParsedODEKernel
    expression = '-3*x - 2*y'
    variable = x
    coupled_variables = y
  [../]

  [./td2]
    type = ODETimeDerivative
    variable = y
  [../]
  [./ode2]
    type = ParsedODEKernel
    expression = '-4*x - y'
    variable = y
    coupled_variables = x
  [../]
[]

[BCs]
  [./all]
    type = FunctionDirichletBC
    variable = u
    boundary = '0 1 2 3'
    function = bc_all_fn
  [../]
[]

[Postprocessors]
  active = 'exact_x l2err_x'

  [./exact_x]
    type = FunctionValuePostprocessor
    function = exact_x_fn
    execute_on = 'initial timestep_end'
    point = '0 0 0'
  [../]

  [./l2err_x]
    type = ScalarL2Error
    variable = x
    function = exact_x_fn
    execute_on = 'initial timestep_end'
  [../]
[]

[Executioner]
  type = Transient
  start_time = 0
  dt = 0.01
  num_steps = 100

  solve_type = 'PJFNK'
[]

[Outputs]
  file_base = ode_sys_impl_test_out
  exodus = true
[]

Example input syntax
Input Parameters