ParsedODEKernel

This scalar kernel adds a source term $var element = document.getElementById("moose-equation-a9eb983e-7322-42a5-a79f-9d9ae905d97f");katex.render("s(u, \\mathbf{v}, \\mathbf{p})", element, {displayMode:false,throwOnError:false});$ : $var element = document.getElementById("moose-equation-e57cac82-4bd3-4f6d-a2db-67e49711fdc2");katex.render(" \\frac{d u}{d t} = s(u, \\mathbf{v}, \\mathbf{p}) \\,,", element, {displayMode:true,throwOnError:false});$ where $var element = document.getElementById("moose-equation-c14533fa-c0d0-4942-93da-2604efbe0800");katex.render("u", element, {displayMode:false,throwOnError:false});$ is the variable the source acts upon, $var element = document.getElementById("moose-equation-0a2601c2-ba3f-4d72-b376-eea359a132ce");katex.render("\\mathbf{v}", element, {displayMode:false,throwOnError:false});$ are other scalar variables, and $var element = document.getElementById("moose-equation-631380cd-3ada-4271-9a73-1041033202b1");katex.render("\\mathbf{p}", element, {displayMode:false,throwOnError:false});$ are post-processor values.

The parameter expression is a string expression for the source term $var element = document.getElementById("moose-equation-ec3ba588-ccdc-4928-aada-d5a63884be06");katex.render("s(u, \\mathbf{v}, \\mathbf{p})", element, {displayMode:false,throwOnError:false});$ as it appears on the left-hand-side of the equation; thus it represents $var element = document.getElementById("moose-equation-520bd83f-df80-457f-8a8f-41fae8df1803");katex.render("-s(u, \\mathbf{v}, \\mathbf{p})", element, {displayMode:false,throwOnError:false});$ . The expression may use the following quantities:

the name of the scalar variable upon which the kernel acts,
the names of any scalar variables specified in the coupled_variables parameter,
the names of any post-processors specified in the postprocessors parameter, and
the names supplied in the constant_names parameter, defined to have the values provided by the constant_expressions parameters.

Currently, the function expression cannot be a function of time.

[ScalarKernels]
  [./td1]
    type = ODETimeDerivative
    variable = x
  [../]

  #
  # This parsed expression ODE Kernel behaves exactly as the ImplicitODEx kernel
  # in the main example. Checkout ImplicitODEx::computeQpResidual() in the
  # source code file ImplicitODEx.C to see the matching residual function.
  #
  # The ParsedODEKernel automaticaly generates the On- and Off-Diagonal Jacobian
  # entries.
  #
  [./ode1]
    type = ParsedODEKernel
    expression = '-3*x - 2*y'
    variable = x
    coupled_variables = y
  [../]

  [./td2]
    type = ODETimeDerivative
    variable = y
  [../]

  #
  # This parsed expression ODE Kernel behaves exactly as the ImplicitODEy Kernel
  # in the main example.
  #
  [./ode2]
    type = ParsedODEKernel
    expression = '-4*x - y'
    variable = y
    coupled_variables = x
  [../]
[]

Input Parameters

expressionfunction expression
C++ Type:FunctionExpression
Unit:(no unit assumed)
Controllable:No
Description:function expression
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

constant_expressionsVector of values for the constants in constant_names (can be an FParser expression)
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:Vector of values for the constants in constant_names (can be an FParser expression)
constant_namesVector of constants used in the parsed expression
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:Vector of constants used in the parsed expression
coupled_variablesScalar variables coupled in the parsed expression.
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:Scalar variables coupled in the parsed expression.
epsilon1e-12Fuzzy comparison tolerance
Default:1e-12
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Fuzzy comparison tolerance
postprocessorsVector of postprocessor names used in the function expression
C++ Type:std::vector<PostprocessorName>
Unit:(no unit assumed)
Controllable:No
Description:Vector of postprocessor names used in the function expression

Optional 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_tagssystemThe tag for the matrices this Kernel should fill
Default:system
C++ Type:MultiMooseEnum
Unit:(no unit assumed)
Options:nontime, system
Controllable:No
Description:The tag for the matrices this Kernel should fill
vector_tagsnontimeThe tag for the vectors this Kernel should fill
Default:nontime
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

disable_fpoptimizerFalseDisable the function parser algebraic optimizer
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Disable the function parser algebraic optimizer
enable_ad_cacheTrueEnable caching of function derivatives for faster startup time
Default:True
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Enable caching of function derivatives for faster startup time
enable_auto_optimizeTrueEnable automatic immediate optimization of derivatives
Default:True
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Enable automatic immediate optimization of derivatives
enable_jitTrueEnable just-in-time compilation of function expressions for faster evaluation
Default:True
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Enable just-in-time compilation of function expressions for faster evaluation
evalerror_behaviornanWhat to do if evaluation error occurs. Options are to pass a nan, pass a nan with a warning, throw a error, or throw an exception
Default:nan
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:nan, nan_warning, error, exception
Controllable:No
Description:What to do if evaluation error occurs. Options are to pass a nan, pass a nan with a warning, throw a error, or throw an exception

Parsed Expression Advanced Parameters

(moose/examples/ex18_scalar_kernel/ex18_parsed.i)

#
# Example 18 modified to use parsed ODE kernels.
#
# The ParsedODEKernel takes expression expressions in the input file and computes
# Jacobian entries via automatic differentiation. It allows for rapid development
# of new models without the need for code recompilation.
#
# This input file should produce the exact same result as ex18.i
#

[Mesh]
  type = GeneratedMesh
  dim = 2
  xmin = 0
  xmax = 1
  ymin = 0
  ymax = 1
  nx = 10
  ny = 10
  elem_type = QUAD4
[]

[Functions]
  # ODEs
  [./exact_x_fn]
    type = ParsedFunction
    expression = (-1/3)*exp(-t)+(4/3)*exp(5*t)
  [../]
  [./exact_y_fn]
    type = ParsedFunction
    expression = (2/3)*exp(-t)+(4/3)*exp(5*t)
  [../]
[]

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

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

[]

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

[ScalarKernels]
  [./td1]
    type = ODETimeDerivative
    variable = x
  [../]

  #
  # This parsed expression ODE Kernel behaves exactly as the ImplicitODEx kernel
  # in the main example. Checkout ImplicitODEx::computeQpResidual() in the
  # source code file ImplicitODEx.C to see the matching residual function.
  #
  # The ParsedODEKernel automaticaly generates the On- and Off-Diagonal Jacobian
  # entries.
  #
  [./ode1]
    type = ParsedODEKernel
    expression = '-3*x - 2*y'
    variable = x
    coupled_variables = y
  [../]

  [./td2]
    type = ODETimeDerivative
    variable = y
  [../]

  #
  # This parsed expression ODE Kernel behaves exactly as the ImplicitODEy Kernel
  # in the main example.
  #
  [./ode2]
    type = ParsedODEKernel
    expression = '-4*x - y'
    variable = y
    coupled_variables = x
  [../]
[]


[BCs]
  [./right]
    type = ScalarDirichletBC
    variable = diffused
    boundary = 1
    scalar_var = x
  [../]

  [./left]
    type = ScalarDirichletBC
    variable = diffused
    boundary = 3
    scalar_var = y
  [../]
[]

[Postprocessors]
 # to print the values of x, y into a file so we can plot it
  [./x_pp]
    type = ScalarVariable
    variable = x
    execute_on = timestep_end
  [../]

  [./y_pp]
    type = ScalarVariable
    variable = y
    execute_on = timestep_end
  [../]

  [./exact_x]
    type = FunctionValuePostprocessor
    function = exact_x_fn
    execute_on = timestep_end
  [../]

  [./exact_y]
    type = FunctionValuePostprocessor
    function = exact_y_fn
    execute_on = timestep_end
    point = '0 0 0'
  [../]

  # Measure the error in ODE solution for 'x'.
  [./l2err_x]
    type = ScalarL2Error
    variable = x
    function = exact_x_fn
  [../]

  # Measure the error in ODE solution for 'y'.
  [./l2err_y]
    type = ScalarL2Error
    variable = y
    function = exact_y_fn
  [../]
[]


[Executioner]
  type = Transient
  start_time = 0
  dt = 0.01
  num_steps = 10
  solve_type = 'PJFNK'
[]

[Outputs]
  file_base = 'ex18_out'
  exodus = true
[]

Input Parameters