Using Automatically Generated Stopping Criteria

Certain stopping criteria are generated automatically when a solver is chosen.

To view the available criteria, expand the Stopping Criteria node.

For steady simulations, there are two automatically-generated stopping criteria:

Maximum Steps
Stop File

For unsteady simulations, there are four automatically-generated stopping criteria:

Maximum Inner Iterations
Maximum Physical Time
Maximum Steps
Stop File

Automatically generated stopping criteria cannot be deleted, but the Enabled property can be activated or deactivated.

Setting the Maximum Number of Inner Iterations

The Maximum Inner Iterations stopping criterion is based on the number of inner iterations that the solver executes for transient analyses.

The node of this criterion has its own properties, and appears when the implicit unsteady model is chosen.

If the implicit unsteady solver is used, this stopping criterion can control the number of inner iterations to be run at each physical time-step. The Maximum Inner Iterations stopping criterion differs from other stopping criteria. This stopping criterion does not control when to stop the solver, only when to stop the inner iterations of the implicit solver and march the solution to the next time-step.

You can change the number of inner iterations by clicking the Maximum Inner Iterations criterion node and then modifying the Max Inner Iterations property.

Maximum Inner Iterations Properties

Enabled

When On, this criterion is used for stopping the solver.

Maximum Inner Iterations

The number of inner iterations before this criterion is satisfied. The default is 5 iterations.

Criterion Satisfied

Indicates if the stopping criterion has been satisfied (read-only).

Logical Rule

Defines how this criterion interacts with other stopping criteria that have been enabled.

AND: Requires that this criterion, along with one or more other criteria with the Logical Rule set to AND, all be satisfied before stopping the solver.
OR: Indicates that satisfying only this criterion is sufficient to stop the solver.

Setting the Maximum Physical Time

The Maximum Physical Time stopping criterion is based on the simulation time that has elapsed in a transient analysis.

The node of this criterion has its own properties, and appears when either the implicit unsteady model or the explicit unsteady model is chosen.

When used with the implicit unsteady model, this stopping criterion is linked to the Time-Step property of the Implicit Unsteady node in the Solvers node. If the Time-Step is set to 1 second, and the Maximum Physical Time is set to 10 seconds, then the simulation runs for 10 time-steps.

To set the maximum time, click the Maximum Physical Time node and modify the Max Physical Time property in the Properties window.

Maximum Physical Time Properties

Enabled

When On, this criterion is used for stopping the solver.

Maximum Physical Time

The amount of physical time before this criterion is satisfied. The default is 1 second.

Criterion Satisfied

Indicates if the stopping criterion has been satisfied (read-only).

Logical Rule

Defines how this criterion interacts with other stopping criteria that have been enabled.

AND: Requires that this criterion, along with one or more other criteria with the Logical Rule set to AND, all be satisfied before stopping the solver.
OR: Indicates that satisfying only this criterion is sufficient to stop the solver.

Setting the Maximum Number of Steps

The Maximum Steps stopping criterion allows you to specify the maximum number of iterations in a steady solver or the maximum number of time-steps in an unsteady solver.

The node of this criterion has its own properties, and is added automatically to the object tree by selecting any of the Time models (Explicit Unsteady, Implicit Unsteady, or Steady).

This criterion cannot be manually deleted.

The stopping decision is based on the number of steps that the solver executes, including any steps that are executed in a previous session. If you Clear the solution, the counter resets to zero, if you initialize the solution it does not.

To change the number of steps, click the Maximum Steps criteria node and modify the value of the Maximum Steps property in the Properties window.

Maximum Steps Properties

Enabled

When On, this criterion is used for stopping the solver.

Maximum Steps

The maximum number of steps to take before this criterion is satisfied. The default is 1000 steps.

Criterion Satisfied

Indicates if the stopping criterion has been satisfied (read-only).

Logical Rule

Defines how this criterion interacts with other stopping criteria that have been enabled.

AND: Requires that this criterion, along with one or more other criteria with the Logical Rule set to AND, all be satisfied before stopping the solver.
OR: Indicates that satisfying only this criterion is sufficient to stop the solver.

Setting a Stop File

The Stop File criterion allows you to specify the pathname of a file (named ABORT by default) that, once in place, causes the solver to stop.

This action can be useful for stopping a batch job, for example. The node of this criterion has its own properties, and is added automatically to the tree by selecting any of the Time models (explicit unsteady, implicit unsteady, or steady).

Note	Activating this criterion does not stop the run immediately because Simcenter STAR-CCM+ checks once every 30 seconds for the stop file.

This criterion cannot be manually deleted.

To set the path name of the file, click the Stop File criterion node and modify the name and the path in the Path property. You can either modify the name directly with a text entry or click the ellipses button and enter the path in the Stop File - Path dialog.

To use this feature while a simulation is running, you can simply add a file as follows:

On Windows, place a file with the correct name in the correct path; even an empty text file would suffice for this purpose.
On Linux, use the line command:
```
% touch ABORT
```

Stop File Properties

Stop Inner Iterations

When On, this criterion responds after the current internal iteration. When Off, this criterion responds when the current time-step is finished (when the appropriate number of internal iterations are complete).

Path

The fully qualified file name of the stop file, ABORT by default.

Enabled

When On, this criterion is used for stopping the solver.

Criterion Satisfied

Indicates if the stopping criterion has been satisfied (read-only).

Logical Rule

Defines how this criterion interacts with other stopping criteria that have been enabled.

AND: Requires that this criterion, along with one or more other criteria with the Logical Rule set to AND, all be satisfied before stopping the solver.
OR: Indicates that satisfying only this criterion is sufficient to stop the solver.

Setting PISO Criteria

The Maximum PISO Correctors stopping criterion sets the Maximum PISO Correctors allowed in an iteration. The PISO Residual Reduction stopping criterion sets the Minimum PISO Correctors for each iteration and the PISO Residual Reduction factor.

You can monitor the number of PISO corrector steps within each time-step using the PISO Correctors Report (see

The nodes for these criteria have their own properties and appears when the PISO Unsteady model is chosen.

Maximum PISO Correctors Properties

Enabled

When On, determines that this criterion is used for stopping the solver. The default is On.

Maximum PISO Correctors

Sets the maximum number of PISO corrector time-steps allowed. The default is 20.

Logical Rule

Defines how this criterion interacts with other stopping criteria that have been enabled.

AND: Requires that this criterion, along with one or more other criteria with the Logical Rule set to AND, all be satisfied before stopping the solver.
OR: Indicates that satisfying only this criterion is sufficient to stop the solver.

Criterion Satisfied

Indicates if the stopping criterion has been satisfied (read-only).

PISO Residual Reduction Properties

Enabled

When On, determines that this criterion is used for stopping the solver. The default is On.

PISO Residual Reduction

The criterion is satisfied when the residual produced by the PISO Unsteady Solver falls to this value. The default is 0.25.

Minimum PISO Correctors

Sets the minimum number of PISO corrector steps required per time-step. The default is 2.

When you specify the minimum number of correctors, PISO performs those corrector steps and then checks for the PISO Residual Reduction stopping criterion. For instance, if the minimum number of correctors is set to 4, PISO might have converged in only two correctors, but the convergence tolerance is checked only after four correctors, so it is forced to do four correctors and PISO leaves with lower convergence tolerance than specified. This helps to bring residuals to lower levels in some problematic local regions.

Logical Rule

Defines how this criterion interacts with other stopping criteria that have been enabled.

AND: Requires that this criterion, along with one or more other criteria with the Logical Rule set to AND, all be satisfied before stopping the solver.
OR: Indicates that satisfying only this criterion is sufficient to stop the solver.

Criterion Satisfied

Indicates if the stopping criterion has been satisfied (read-only).

Disabling/Enabling Stopping Criteria

To deactivate an automatically generated stopping criterion, click the criterion node and deactivate the Enabled property in the Properties window.

All criteria can be activated or deactivated at the same time. To activate or deactivate all criteria, right-click the Stopping Criteria node and select Enable All Criteria or Disable All Criteria respectively.