ConstantDT

Timestepper that takes a constant time step size

Description

The ConstantDT TimeStepper simply takes a constant time step size throughout the analysis, unless the solver fails to converge on an iteration.

ConstantDT begins the analysis taking the step specified by the user with the dt parameter. If the solver fails to obtain a converged solution for a given step, the executioner cuts back the step size and attempts to advance the time from the previous step using a smaller time step. The time step is cut back by multiplying the time step by 0.5.

If the solution with the cut-back time step is still unsuccessful, the time step size is repeatedly cut back until a successful solution is obtained. The user can specify a minimum time step through the dtmin parameter in the Executioner block. If the time step must be cut back below the minimum size without obtaining a solution, the problem exits with an error. If the time step is cut back using ConstantDT, that cut-back step size will be used for the remainder of the the analysis.

Example Input Syntax

[Executioner]
  type = Transient
  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'
  line_search = none
  nl_rel_tol = 1e-6
  nl_max_its = 10
  l_tol = 1e-8
  l_max_its = 50
  num_steps = 2 # 200
  nl_abs_tol = 1e-10
  nl_rel_step_tol = 1e-10
  nl_abs_step_tol = 1e-10
  [./TimeStepper]
    type = ConstantDT
    dt = 0.001
  [../]
  dtmin = .001
[]
(test/tests/misc/check_error/wrong_displacement_order.i)

Input Parameters

  • dtSize of the time step

    C++ Type:double

    Options:

    Description:Size of the time step

Required Parameters

  • reset_dtFalseUse when restarting a calculation to force a change in dt.

    Default:False

    C++ Type:bool

    Options:

    Description:Use when restarting a calculation to force a change in dt.

  • growth_factor2Maximum ratio of new to previous timestep sizes following a step that required the time step to be cut due to a failed solve.

    Default:2

    C++ Type:double

    Options:

    Description:Maximum ratio of new to previous timestep sizes following a step that required the time step to be cut due to a failed solve.

Optional Parameters

  • control_tagsAdds user-defined labels for accessing object parameters via control logic.

    C++ Type:std::vector

    Options:

    Description:Adds user-defined labels for accessing object parameters via control logic.

  • enableTrueSet the enabled status of the MooseObject.

    Default:True

    C++ Type:bool

    Options:

    Description:Set the enabled status of the MooseObject.

Advanced Parameters

Input Files