How to interrupt a transient Fluent simulation based on a target criterion?

This article will inform the reader on how to use an execute command with a report definition to interrupt a transient Fluent simulation.  The Convergence Conditions feature of Fluent can be used to solve a transient model and interrupt that solution when a target is reached.  The Convergence Conditions feature may cause Fluent to solve all iterations at each time step.   Although sub-iterations may achieve convergence from a residuals point of view, the iterations will continue until the maximum number of iterations is reached.   This article provides a way to interrupt a solution based on a report definition target while allowing the sub-iterations to move on to the next time step immediately after residual convergence is achieved. 

The method shown here is for an example two-species simulation of air and water vapor.  It is desired to interrupt the simulation when the mass-weighted average water vapor species mass fraction reaches 0.22 on a section plane. 

Steps 

1. Create a Report Definition.  Activate the “Create Output Parameter” checkbox at bottom left.
   
    
2. Confirm that the Output Parameter is in the Parameters & Customization group near the bottom of the Outline View. 
   
3. Enter the Calculation Activities > Execute Commands section to create a New command
   
4. Enter a command to be Executed Repeatedly at a Every 1 (or more) Time Steps.  The following example instructs Fluent to get the output parameter value of the aveh2o report and check if it is greater than 0.22.  If it is then a “set! mstop?” flag is set to true.  This stops the solution. 
   (if (>  (get-output-parameter-value "aveh2o-op") 0.22) 
   (set! mstop? #t)) 

 
The following image demonstrates that the sub-iterations are converging, and that Fluent moves on to the next time step when that convergence is reached.  It also shows the solution stops on its own when the mstop flag is set to true by the execute command.