TimestepPostprocessor

Selects the simulation timestep size based on whether a target postprocessor has exceeded a tolerance

Description

TimestepPostprocessor selects between two timestep sizes based on whether a target postprocessor has crossed a tolerance, typically used to shrink the timestep once a significant event (e.g. thermal breakthrough) has been detected. On the first timestep where targetpostprocessor reaches enthalpy_relative_tolerance, an internal trigger latches; the latch is permanent for the rest of the simulation and is preserved across restarts. Before the trigger latches, the reported value is dt_before_trigger (default 2592000 s, i.e. one month); from the triggering timestep onward (inclusive), it is dt_after_trigger (default 10800 s, i.e. six hours).

Because this postprocessor merely reports a value, it must be supplied as the postprocessor parameter of a PostprocessorDT (or similar) [TimeSteppers]/[Executioner] timestep sizing mechanism to actually control the simulation's timestep.

Example Input Syntax

[Postprocessors<<<{"href": "../../syntax/Postprocessors/index.html"}>>>]
  [target]
    type = FunctionValuePostprocessor<<<{"description": "Computes the value of a supplied function at a single point (scalable)", "href": "FunctionValuePostprocessor.html"}>>>
    function<<<{"description": "The function which supplies the postprocessor value."}>>> = target_fn
  []
  [computed]
    type = TimestepPostprocessor<<<{"description": "Selects the simulation timestep size based on whether a target postprocessor has exceeded a tolerance", "href": "TimestepPostprocessor.html"}>>>
    targetpostprocessor<<<{"description": "The name of the targetpostprocessor"}>>> = target
    enthalpy_relative_tolerance<<<{"description": "Threshold value of targetpostprocessor at or above which the trigger latches (compared directly against the postprocessor value, not as a relative difference)"}>>> = 3.5
    dt_before_trigger<<<{"description": "The timestep size to use before the trigger fires (Default is 2592000 s, i.e. 1 month)"}>>> = 100
    dt_after_trigger<<<{"description": "The timestep size to use after the trigger fires (Default is 10800 s, i.e. 6 hours)"}>>> = 10
  []
  [exact]
    type = FunctionValuePostprocessor<<<{"description": "Computes the value of a supplied function at a single point (scalable)", "href": "FunctionValuePostprocessor.html"}>>>
    function<<<{"description": "The function which supplies the postprocessor value."}>>> = exact_fn
  []
  [residual]
    type = ParsedPostprocessor<<<{"description": "Computes a parsed expression with post-processors", "href": "ParsedPostprocessor.html"}>>>
    pp_names<<<{"description": "Post-processors arguments"}>>> = 'computed exact'
    expression<<<{"description": "function expression"}>>> = 'abs(computed - exact)'
  []
[]

Input Parameters

targetpostprocessorThe name of the targetpostprocessor
C++ Type:PostprocessorName
Unit:(no unit assumed)
Controllable:No
Description:The name of the targetpostprocessor

Required Parameters

dt_after_trigger10800The timestep size to use after the trigger fires (Default is 10800 s, i.e. 6 hours)
Default:10800
C++ Type:Real
Unit:(no unit assumed)
Range:dt_after_trigger > 0
Controllable:No
Description:The timestep size to use after the trigger fires (Default is 10800 s, i.e. 6 hours)
dt_before_trigger2.592e+06The timestep size to use before the trigger fires (Default is 2592000 s, i.e. 1 month)
Default:2.592e+06
C++ Type:Real
Unit:(no unit assumed)
Range:dt_before_trigger > 0
Controllable:No
Description:The timestep size to use before the trigger fires (Default is 2592000 s, i.e. 1 month)
enthalpy_relative_tolerance0.01Threshold value of targetpostprocessor at or above which the trigger latches (compared directly against the postprocessor value, not as a relative difference)
Default:0.01
C++ Type:Real
Unit:(no unit assumed)
Controllable:No
Description:Threshold value of targetpostprocessor at or above which the trigger latches (compared directly against the postprocessor value, not as a relative difference)

Optional Parameters

allow_duplicate_execution_on_initialFalseIn the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).
Default:False
C++ Type:bool
Controllable:No
Description:In the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).
execute_onTIMESTEP_ENDThe list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html.
Default:TIMESTEP_END
C++ Type:ExecFlagEnum
Options:XFEM_MARK, NONE, INITIAL, LINEAR, LINEAR_CONVERGENCE, NONLINEAR, NONLINEAR_CONVERGENCE, POSTCHECK, TIMESTEP_END, TIMESTEP_BEGIN, MULTIAPP_FIXED_POINT_END, MULTIAPP_FIXED_POINT_BEGIN, MULTIAPP_FIXED_POINT_CONVERGENCE, MULTISYSTEM_FIXED_POINT_ITERATION_END, FINAL, CUSTOM, TRANSFER
Controllable:No
Description:The list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html.
execution_order_group0Execution order groups are executed in increasing order (e.g., the lowest number is executed first). Note that negative group numbers may be used to execute groups before the default (0) group. Please refer to the user object documentation for ordering of user object execution within a group.
Default:0
C++ Type:int
Controllable:No
Description:Execution order groups are executed in increasing order (e.g., the lowest number is executed first). Note that negative group numbers may be used to execute groups before the default (0) group. Please refer to the user object documentation for ordering of user object execution within a group.
force_postauxFalseForces the UserObject to be executed in POSTAUX
Default:False
C++ Type:bool
Controllable:No
Description:Forces the UserObject to be executed in POSTAUX
force_preauxFalseForces the UserObject to be executed in PREAUX
Default:False
C++ Type:bool
Controllable:No
Description:Forces the UserObject to be executed in PREAUX
force_preicFalseForces the UserObject to be executed in PREIC during initial setup
Default:False
C++ Type:bool
Controllable:No
Description:Forces the UserObject to be executed in PREIC during initial setup

Execution Scheduling 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:Yes
Description:Set the enabled status of the MooseObject.
outputsVector of output names where you would like to restrict the output of variables(s) associated with this object
C++ Type:std::vector<OutputName>
Controllable:No
Description:Vector of output names where you would like to restrict the output of variables(s) associated with this object
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
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

prop_getter_suffixAn optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.
C++ Type:MaterialPropertyName
Unit:(no unit assumed)
Controllable:No
Description:An optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.
use_interpolated_stateFalseFor the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.
Default:False
C++ Type:bool
Controllable:No
Description:For the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

Material Property Retrieval Parameters

Input Files

(test/tests/postprocessors/timestep_postprocessor/inp.i)

(test/tests/postprocessors/timestep_postprocessor/inp.i)

# Analytic verification of TimestepPostprocessor.
#
# TimestepPostprocessor::execute() latches a boolean trigger the first time
# targetpostprocessor >= enthalpy_relative_tolerance:
#   triggered = true
# getValue() then returns dt_before_trigger while !triggered, or dt_after_trigger once the
# trigger has latched (note triggered is set in execute() before getValue() is called on the
# same timestep, so the trigger step itself already reports dt_after_trigger).
#
# Drive targetpostprocessor(t) = t, enthalpy_relative_tolerance = 3.5,
# dt_before_trigger = 100, dt_after_trigger = 10, dt = 1, num_steps = 6:
#
#   t=1,2,3: value=1,2,3 < 3.5 -> not latched      -> getValue = 100
#   t=4:     value=4 >= 3.5 -> latch triggered     -> getValue = 10  (trigger step)
#   t=5,6:   already latched                        -> getValue = 10
#
# so exact(t) = if(t < 4, 100, 10).

[Mesh/mesh]
  type = GeneratedMeshGenerator
  dim = 1
[]

[Problem]
  kernel_coverage_check = false
  solve = false
[]

[Functions]
  [target_fn]
    type = ParsedFunction
    expression = 't'
  []
  [exact_fn]
    type = ParsedFunction
    expression = 'if(t < 4, 100, 10)'
  []
[]

[Postprocessors]
  [target]
    type = FunctionValuePostprocessor
    function = target_fn
  []
  [computed]
    type = TimestepPostprocessor
    targetpostprocessor = target
    enthalpy_relative_tolerance = 3.5
    dt_before_trigger = 100
    dt_after_trigger = 10
  []
  [exact]
    type = FunctionValuePostprocessor
    function = exact_fn
  []
  [residual]
    type = ParsedPostprocessor
    pp_names = 'computed exact'
    expression = 'abs(computed - exact)'
  []
[]

[Executioner]
  type = Transient
  dt = 1
  num_steps = 6
[]

[Outputs]
  csv = true
[]