7 Replies Latest reply on Aug 24, 2016 5:09 PM by Boyko Tchavdarov

    Parametric study needs recalculation for newly added results?

    Mar Gai
    Mar Gai Aug 18, 2016 9:42 AM

      Hello,

      I tried to use parametric studies to determine the pressure drop over a valve for different mass flows. I expected that parametric studies need less computation time than doing the variants manually.

      But I discovered two problems:

       

      1. The computation time for each single scenario is similarly long as the computation time for the original project. Is this true?

       

      2. If I have calculated the different scenarios, and afterwards want to look at a different result parameter (e.g. a velocity...), this newly selected result parameter does NOT appear before I recalculate all the scenarios, needing again the full computation time ! Is this normal, or am I doing something wrong?

       

      Thanks

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        • Re: Parametric study needs recalculation for newly added results?
          Boyko Tchavdarov
          Boyko Tchavdarov Aug 18, 2016 11:49 AM (in response to Mar Gai)

          Hi Mar,

          1) The computational time of the same model depends on the initial conditions and on the convergence criteria. Check that they are the same in your First Point of the Parametric Study. Each next point may take the previous result or not (default initial guess) depending on whether you have check the corresponding box.

           

           

          2) You have to plan ahead which field variable will be of interest in your Study (Pressure, velocity, turbulent intensity, etc). Although all field variables will be computed in a Parametric Study only the selected filed variables will be output in a result file for post-processing. This saves space & time in writing./reading large result files.

          • Re: Parametric study needs recalculation for newly added results?
            Amit Katz
            Amit Katz Aug 18, 2016 4:07 PM (in response to Mar Gai)

            Parametric study will re-run the entire calculation. All you save is meshing time and the inconvenience of setting up multiple copies of the same simulation with slight tweaks. After you have your results you can do a trend analysis on the data in a program such as Excel to obtain an interpolation relationship.

              • Re: Parametric study needs recalculation for newly added results?
                Mar Gai
                Mar Gai Aug 19, 2016 7:44 PM (in response to Amit Katz)

                Thank you both!

                 

                I consider it a bug that you can't add further output variables once the calculation has been done. What did I spend all that computation time for? ;-)

                 

                So parametric study is suitable only for small problems where calculation time doesn't matter much, or for very many scenarios where manual takeover of the results becomes a nuisance.

                For bigger problems (with not so many different scenarios) I will use batch processing of many (manually adjustet) seperate projects instead, because only that way can I add further output variables later on.

              • Re: Parametric study needs recalculation for newly added results?
                Boyko Tchavdarov
                Boyko Tchavdarov Aug 19, 2016 10:33 AM (in response to Mar Gai)

                Some more details on the Parametric Study. If ones the Parametric Study is has been run and then repeated  it will e-run all the Design Points (runs in the Study) only if "Recalculate" Box is checked under the Scenario Tab.

                One disadvantage of the Parametric Study in "What if Scenario" is there is no option to chose arbitrary Initial Data for each Design Point in contrast to multiple CFD-Configuration of the Project (CFD Model) where one can chose any result file (configuration) to transfer the initial data. I have submitted an SPR on the same some years ago to add a choice of selecting any result file for Initial Data of the Design Point in the Scenario Tab but it is not there in SW2017. . For the above reason the Parametric Study is not as usable as it could be. because the time of completing any CFD runs depends strongly of the Initial Data passed to the Solver.

                 

                In what's new in SW2017 it is claimed that by thr Optimization variant of the Parametric Study we can minimize maximize a goal (finally !) but I could not find that option. I created an SR on the same and will update this Q by the SW Support team answer.