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-   -   convergence criteria by lift and drag coefficent (http://www.cfd-online.com/Forums/cfx/86221-convergence-criteria-lift-drag-coefficent.html)

xtof March 17, 2011 06:37

convergence criteria by lift and drag coefficent
 
Hello,

I have modelled a flow over an airfoil in cfx which works fine so far. Futhermore i have created monitorpoints for lift- and drag-coefficent.
What i want to do now is to set a interrupt control condition in cfx pre so that the actual value of the coefficent is compared to the one ten iterations before. If the difference is under a defined limit (let's say 0.1%) the simulation should be stoped.
My problem is that I don't know the CEL-Syntax to get a value at a certain iteration.

Maybe somebody knows how to program that.

Thanks

ghorrocks March 18, 2011 07:44

This cannot be done easily in CEL.

You will probably find a residual convergence tolerance to correspond to your coefficient convergence. Then you could just use a simple residual convergence tolerance.

If you insist on using your coefficients to judge convergence then I would have a cron job running in the background (ie outside of CFX) which monitors the monitor point output files and when it senses convergence it runs the cfx5stop command.

xtof March 18, 2011 07:50

Thanks for the reply. I think I'll go with the normal residuals so far. I had a phoncall with the CFX-Support yesterday and they told me the same. Maybe when I have more time I'll try to pragramm some tool to monitor the coeffiecents and stop the solver run.

joey2007 March 18, 2011 15:38

The service send me an user fortran example, which stores older values, some time ago. I am not permitted to distribute further, however you may get it if you ask.


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