9 Replies Latest reply on Jul 15, 2014 8:03 PM by Jared Conway

    Flow sim still slow after HDD wipe

    Thomas Murray

      Hey  All,

       

      I'm new to SW FLow Simulation, and I was just wondering if there are settings that I'm missing to speed up the flow simulation. I just completely wiped the hard drive to increase system resources but flow simulation still seems slow. I am running 36 GB RAM, on a dual core Xeon 2.3 GHz processor. Im working off of a local drive but the internet here is really slow (not sure if that's a factor).

       

      I am loading the assemblies lightweight, removed shadows, increased windows virtual memory to triple the RAM capacity. Done these things but the system still seems to drag. Is this just truly the nature of flow simulations??? (Just having a cylinder spin inside of a housing filled with oil and trying to determine drag and power loss).

       

      Windows task manager says 6% CPU utilization and only 5.3 GB of RAM being used. I feel like I am missing something here. Pls comment.

       

      -t

        • Re: Flow sim still slow after HDD wipe
          Nicholas Luyster

          Hi Thomas,

           

          The Internet shouldn't matter if you're working locally and those specs look decent enough.

           

          My question for you is what version of SolidWorks are you running and what stage of the run is slow?

           

          Earlier versions of SolidWorks could do multithreading with the solve but not with the mesh.  If you're on the latest version of SolidWorks, I believe the mesh makes use of multithreading. 

           

          I hope this helps.

           

          All the best,

           

          Nick Luyster

          Gosimulation.com

          Online SolidWorks Simulation Training

          • Re: Flow sim still slow after HDD wipe
            Jared Conway

            version/service pack?

             

            how many cells?

             

            steady state or transient?

             

            what physics are included?

             

            what is the solve time? what solve are you hoping to get?

             

            is hyperthreading enabled or disabled?

              • Re: Flow sim still slow after HDD wipe
                Jared Conway

                also, what made you wipe the system to speed things up?

                 

                does the system generally perform well? like if you run a solidworks benchmark or perfmark, does it seems within reason?

                  • Re: Flow sim still slow after HDD wipe
                    Thomas Murray

                    Hi Jared,

                     

                    The version of solidworks is SW2012 SP1. The reason for the wipe was the simulation and solidworks at large would act strange, and not solve simple flow cases. Then I tried to uninstall SW and it would hang for days during the uninstallation process. It seems to be working now.

                     

                    What did you mean by steady state? The physics is a rotor/stator pair in an oil filled housing with the rotor moving at 1000 RPM. I am solving for the torque drag and power loss due to the fluid upon the rotor (using torque surface goals on the axis of rotation).

                    The strange thing is, I started to see progress on the mesh when I logged back into my computer this morning.

                     

                    1) Does it stop or slow down at log off?

                    2) Should I place a priority on 'background processes' or 'programs' in the performance menu for windows, or does that matter?

                    3) What do you think is a reasonable solve time for 9M cells on an average system?

                    4) Why 7% CPU utilization? Seems super low for CFD.

                     

                    help1.png

                      • Re: Flow sim still slow after HDD wipe
                        Nicholas Luyster

                        Hi Thomas,

                         

                        In 2012, only one core is used during meshing. That's why only 7% of your CPU is working while this picture was taken. 

                         

                        9,000,000 cells is a lot.  It's going to take a really long time to solve no matter what.  It might be best to start out with a course mesh and then converge your results by running several simulation and converging your mesh.  I say this because with 9M cells, there are probably a few cells which are unnecessaraly fine and it may be hurting your performance.

                         

                        If you upgraded to the most recent version, I think you'd notice that the mesh goes much quicker.  I'm sure your VAR would be happy to run a comparative speed test for you.

                         

                        All the best,

                         

                        Nick Luyster

                        Gosimulation.com

                        Online SolidWorks Simulation Training

                          • Re: Flow sim still slow after HDD wipe
                            Jared Conway

                            thomas, are you using rotating regions or moving wall?

                             

                            do you really need 9m cells?

                             

                            but like nick said, you're using old tech, looks like hyperthreading is turned on, you're probably going to reevaluate your goals here to decide on next steps. but from everything you're mentioned, things are working as expected

                             

                            we do a lot of mentoring for customers like you where we take their model that takes forever to solve and get it down to reasonable solve times with the same level of accuracy. for example we just worked with a customer who's analysis took days, brought it down to 1hr by setting it up differently.

                    • Re: Flow sim still slow after HDD wipe
                      Thomas Murray

                      Thanks both of you guys for your comments. I certainly have reduced my cells count down to 1.1 million. I ended up with 9M cells because I opted for narrow channel refinement on the 'initial mesh'. Also, my smallest gap is 1.27 mm which is pretty small, so I placed a 'local inital mesh' around it setting the gap size to its actual value and used lvl 3 mesh (with narrow channel refinement here as well). Like Nick has stated, I will have to see if the values converge with a finer mesh later.

                       

                      The system is a rotating wall, I wasn't really clear on what a rotating region was and its effect on the results. Do you think using a rotating region and/or symmetry for something like this would help reduce solve time? I suppose I can do some tests.

                       

                      My new setup is still using the initial, local inital mesh, and rotating wall. I turned off narrow channel refinement for the initial mesh, but left it on the local mesh and reset the gap size to 6 mm. I doubt this will provide correct results because the gap size is way smaller.

                       

                      Just curious how would you guys set it up (ie rotating region, local or just an initial mesh, and what level mesh and gap size?)