4 Replies Latest reply on Mar 29, 2017 9:43 AM by Tiago Antonio

    Changing the time step on Solidworks 2016 Flow Simulation

    Tiago Antonio

      Hello,

      I need to do some transient fluid flow simulations of a component for my master thesis and currently I'm stuck with an issue. For my project I have to run simulations of some seconds, and I need no less than 0.1s for my time step. The issue is that when I run the simulation the time step appears as you can see on the image below. Time steps of about 5E10^-5, wich result in calculation times of about 30h+. It's a lot. I've already set a manual time step of 0.1s under time step settings, in calculation control options>solving and this behavior remains. What am I missing here? I would apreciate some help because I need to run quite a few simulation and with this issue it would take me weeks to run them. I'm running Solidworks 2016.

      Thank you very much in advance,

      Tiago Antonio

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        • Re: Changing the time step on Solidworks 2016 Flow Simulation
          Bill McEachern

          The time step is dynamic and will change so the actual solve time maybe a lot less than 30 hours and is an estimate at best. More help could be provided with some description of the problem to be solved. For instance, if the object is the diffusion of some quantity, like heat, then the use of flow freezing can speed up the calc substantially but it depends on what you are doing and whether the technique is appropriate. Just mucking with the time step directly can lead to the computation of non realistic results if the situation is not well understood.

          • Re: Changing the time step on Solidworks 2016 Flow Simulation
            Ryan Navarro

            Are you sure you didn't set the 0.1 seconds under Calculation control -> Saving by accident?

            That field controls how many plot steps get saved but doesn't affect the calculation time step

             

            If you set it under Calculation Control -> Solving you will need to change Time Step -> Auto to Manual and then input a calculation time step size there

            • Re: Changing the time step on Solidworks 2016 Flow Simulation
              Mark Keown

              Below are some tips that I use.

              1. Set up solving as shown.  If the solve goes over the physical time you may increase the % required for solving.

              If you only tick Physical time the solve will be fast.

              2. Enter manual (suggested time step) - but as discussed by others Flow will calculate this.

              In this example the 300 s 'step' is what will be exported to excel.

              3.  Full Results 'step' is what you can select under Results time step (to show section plots etc) (right click results and select the time step).  In this example every 3600 s is saved.  If the save value is small the solve will take ages - so make the Period as large as reasonable.

              My preference is not to use freezing... but you can test this.

              Solve with course mesh settings until you get the bugs out.  Then increase mesh slowly until you only get a small change between the previous solve and the finer mesh.

              If you can do share your model.

              *Let us know what your solution is...*

              • Re: Changing the time step on Solidworks 2016 Flow Simulation
                Tiago Antonio

                Guys, first of all let me thank you for trying to help me promptly. My project is to study the flow in a T shaped junction, in wich two fluids enter in opposite ends, they mix, and exit on the other end ( I'll post a snap later). The flow occurs at a very low Re so it is strongly laminar. As we have almost no advection, the mixing is strongly diffusive, so it means that it is hard to get a efficient mix in a short time. The solution we're testing is to have pulsed flows with opposite phase on both ends. That's what I'm trying to simulate. First of all let me tell you that for some reason I don't have flow freezing option in solve options. I've also read about the possibility to use "nested iterations". Is this for me?

                Thank you again for your help with this issue