tem_convergence_module Module

This module contains type definition and routines for convergence to decide steady state status.

convergence may be a single table with the definition of the convergence parameters or it might be a table of tables with each holding the definition of a convergence criterion.

The general convergence definition looks like this:

  convergence = {
    variable = {'density', 'pressure'},
    time_control = {
      min = 0,
      max = {sim = 10.0},
      interval = {iter = 1}
    },
    shape = {kind='all'},
    reduction = {'average', 'average'},
    norm = 'average',
    nvals = 10,
    absolute = true,
    condition = {
      {threshold = 1.e-15, operator = '<=' },
      {threshold = 1.e-12, operator = '<=' }
    }
  }

variable needs to be a list of variables from the variable system, providing the quantities that are to checked for convergence.

time_control needs to be a time control definition, see tem_timeControl_module it defines the timespan within which the convergence check should be active. Its interval setting describes when to perform the necessary operations to decide whether a steady state is reached.

shape needs to be shape definition to describe a subsection of the overall domain in which the check for convergence is to be done (might be {kind='all'} to take the complete simulation domain into account. See tem_shape_module for more details.

reduction needs to be a table of spatial reduction definitions for each variable. Typical reduction operations could be average, sum and l2norm. This reduction is applied to obtain a single value for the convergence decision across all elements within the domain section defined by shape. See tem_reduction_spatial_module for more details.

norm describes how to treat the spatially reduced values over time. There are two options: 'simple' will just compare the current value with the one from the last check. 'average' will build the average over the nvals last values that have been obtained via the spatial reduction. Default of this setting is to use the simple comparison.

nvals is a setting used if norm = 'average' and sets the size of the sliding window in the historical data across which an average will be made to obtain the value to compare against in the current check.

absolute denotes whether to use an absolute or relative measure to make the comparisons provided in the condition setting. The default is false that which results in a relative measure. Relative means here, that the difference of the current value and the comparison value is checked against the threshold multiplied with the current value instead of using the threshold itself directly.

use_get_point indicates whether to use individual points to obtain the values or whole elements. Default is false, so the complete state of elements in the shape will be used to find the reduced values.

ndofs describes how many degrees of freedom to use from elements if use_get_point is false. The default is to use all degrees of freedom, which can be indicated by setting ndofs = -1.

condition needs to be table providing the condition under which convergence is assumed for each variable. The condition is defined by a threshold and an operator. See tem_condition_module for details.

Convergence is assumed if all variables defined in the convergence table meet their defined definition. To check for convergence a reduction and condition has to be defined for each variable that is to be considered for the steady state check.