17 Replies Latest reply on Feb 13, 2015 2:59 PM by Jared Conway

    I get different results for the same meshing when I run solve each time.

    Manjunath Anand

      Hello Experts,

       

      I am running an internal analysis for a radial blower design. For the same meshing quality level and same settings, I get different (random) results each time I run the "solve" command. I ran into this problem when I could not reproduce the same results with all settings being the same. Does anyone experienced the same? Any help or suggestion would be highly appreciable.

       

      Thanks

      Manjunath

        • Re: I get different results for the same meshing when I run solve each time.
          Jared Conway

          you're saying the workflow is

          setup problem > run > results

          run again > results

          and both are different?

          what specifically is different?

          what are the convergence graphs like?

          • Re: I get different results for the same meshing when I run solve each time.
            Manjunath Anand

            Copy & paste from another forum where a user by name "Murph" has replied to my query. Could be useful to someone in the forum here.

            ----------------------------------------------------------

            manjunathanand,

             

            I have seen your thread and re-ran a model that I have involving an internal analysis with an idealized fan. I have the same problem, that the simulation is showing a different result even though I have the same setup and am running on the same machine. My results are close, however this should not be happening at all. It means my results are useless in this case.

             

            I have sent my model to SW support who have sent to SW vendor. They have confirmed that this shouldn't be happening. Initially they have told me that it is something to do with the way SW distributes to multiple processors - they are looking into the issue as a matter of urgency. So they have accepted a fault in the software and are trying to address it as we speak.

             

            I saw your post and thought it off becuase...

             

            The solidworks solvers should give you the EXACT same result if you are simulating on the same machine. SW runs on the RANS (or DNS) equations and they are deterministic ie... same input should give you the exact same output (your convergence plots should look the same - exactly the same).

             

            If you are on a different machine or OS - the result may differ slightly due to rounding differences of different systems. CFD software that runs on multiple platforms will run on multiple platforms, but will give slightly different results. They should be close to the same answer.

             

            If your answers are way off, it is likely that you have a psudo-steady or unsteady system in reality. But given the error in the software - it may be impossible to say! In this case you may find difficultly getting any meaningful results from SW Flow sim.

             

            It would help if you would also pass ur simulation onto the SW vendor. This will help them diagnose and fix the issue.

             

            Try ur simulation again on a single core (turn of all but one core in BIOS if you can). If the problem is due to issues with multi-processing, you then might be able to get some results. if you do this let me know!

             

            ----------------------------------------------------------