2 Replies Latest reply on May 18, 2018 8:48 AM by Janko Stellaard

    How does flow simulation calculate average, delta, criterion, min, and max values?

    David McCullough

      I am curious how flow simulation calculates the values for average, delta, minimum, maximum, and criteria? Are the values computed over the entire solve process or over the convergence interval? It seems to me the values are somewhere in between the entire solution and the convergence interval. Is there anything in the help files that explains this? I am unable to find it.

       

      My biggest concern and what sparked this question is delta is not equal to the difference between the minimum and maximum values. My understanding of researching this so far is that delta is supposed to be the difference between min and max.

       

      I do not have a screenshot of the goal plot or goal list at this time, I will have to upload it later tonight. I just wanted to go ahead and ask in case someone is familiar with this.

        • Re: How does flow simulation calculate average, delta, criterion, min, and max values?
          Janko Stellaard

          From the SW knowledge base:

           

          Goal's progress bar is a qualitative and quantitative characteristic of the goal's convergence process. When the Flow Simulation software analyses the goal convergence, the SOLIDWORKS Flow Simulation software calculates the goal amplitude excursion of the averaged value with a definition as the difference between the maximum value and the minimum value of the averaged goal over the analysis interval from the reckoning of the last iteration. The SOLIDWORKS Flow Simulation software then compares this amplitude excursion with the goal-convergence criterion amplitude excursion. The goal-convergence criterion amplitude excursion is either your specification or an automatic determination from the SOLIDWORKS Flow Simulation software as a fraction of the physical parameter amplitude excursion of the goal over the computational domain.

           

          The percentage of the goal- convergence criterion amplitude excursion to the goal real amplitude excursion over the analysis interval appears in the goal convergence progress bar.

           

          When the goal real amplitude excursion becomes equal to or smaller than the goal-convergence criterion amplitude excursion, the word "achieved" appears in place of the progress bar. Naturally, if the goal's real amplitude excursion oscillates, the progress bar oscillates as well. Moreover, it may noticeably regress, in particular from the "achieved" status. The calculation finishes if the iterations (in travels) required for finishing the calculation have been performed, as well as if the goals' convergence criteria are satisfied before performing the required number of iterations. So, the goal's progress bar together with the goal's plot is useful for inspecting the goal's behaviour during the calculation.

           

          The permissible value of the goal’s averaged value amplitude excursion (in the goal’s units) over the Analysis interval reckoned backward from the current iteration. So, when the goal’s amplitude excursion over this interval becomes lower than this value, the goal is considered as converged. If users clear the On/Off check box for a specific goal, this goal will not influence the task convergence. If users clear the On/Off check box for all specified goals, the task convergence will be only governed by the SOLIDWORKS Flow Simulation internal convergence criteria.

            • Re: How does flow simulation calculate average, delta, criterion, min, and max values?
              Janko Stellaard

              In addition:

               

              How does the SOLIDWORKS Flow Simulation software calculate the ‘Goals convergence’ criterion when I select the ‘[auto]’ option on the ‘Finishing’ tab of the ‘Calculation Control Options’ menu?

               

              The standard definition for the ‘Criteria’ is documented in the Online Users Guide at ‘Help’ > ‘SOLIDWORKS Simulation’ > ‘Flow Simulation Help Topics’. However, for projects with a total mesh cell count of less than 5000, the criteria is 15% instead of 3% from ‘Max-Min’ during the first travel period starting with the third iteration. The automatic criterion changes linearly from 3% to 15% as the number of cells decreases from 15000 to 5000.