3 Replies Latest reply on Feb 6, 2015 6:07 PM by Jared Conway

    Too long computation time

    Pradip Aryal
    Pradip Aryal Feb 4, 2015 1:42 AM

      Hello all

      I am using flow simulation; HVAC module to analyze distribution of temperature, velocity, PMV and Co2 in a classroom of dimension 38m*28m*3m where the conditioned air is provided via 35 square diffuser. Various heat sources and humans generating C02 is modeled inside classroom. Auto mesh generation with level of initial mesh 5 and minimum gap size of 0.012m is done. There are 1.4 million fluid cells and 1.3 million of partial cells and after running simulation for 35 hour, the CPU time left is more than 100 hour with 0% progress. Is there a way to reduce computational time without compromising in accuracy ? I am interested in the distribution of thermal comfort parameters (PMV, temp, Vel, co2) in occupied region of height 1.1m. The global goals assumed are average mean radiant temperature, operative temperature, velocity and volume fraction of co2.

      Regards,

        • Re: Too long computation time
          Jared Conway
          Jared Conway Feb 4, 2015 1:45 PM (in response to Pradip Aryal)

          "Is there a way to reduce computational time without compromising in accuracy ?" > would be a million dollar idea

           

          i would recommend you start with a much coarser mesh, see what you results look like

          then bump it up a bit see how much they change

           

          if htey don't change significantly you may not need 3 million cells to solve the problem

           

          35hrs for a 3 million cell problem seems like a lot, what are teh computer specs?

           

          135hrs for 3 million cells seems very wrong, what are you trying to use as your convergence criteria?

            • Re: Too long computation time
              Pradip Aryal
              Pradip Aryal Feb 5, 2015 2:09 AM (in response to Jared Conway)

              Hello Jared,

              Computer specs are pretty good. Its Intel Xeon 3.7 GHz with 8 core and 32 GM of RAM. Convergence criteria was set automatic. Geometry check was fine but Could it be a problem with my solid modeling? (too many solid structure inside with some of them imported from CAD) Picture attached

              Thankfully,

              Prad

              1.png2.png3.png

                • Re: Too long computation time
                  Jared Conway
                  Jared Conway Feb 6, 2015 6:07 PM (in response to Pradip Aryal)

                  from a model perspective, only suggestion would be to simplify the people further

                  otherwise the model looks ok

                  remember that you don't have to wait for full convergence, you can stop it early

                  average parameters might be challenging to converge fully with a turbulent environment. maxes are sometimes better. (Even if average is your goal)

                  take a look at the actual plots to see how much it is actually changing