2 Replies Latest reply on Nov 7, 2013 7:56 AM by Mike Peppard

    Fluid Subdomains with External Analysis

    Mike Peppard

      Is there a way to set the inital conditions of a volume or "Fluid Subdomain" and run it in an external analysis?

       

      An simple example that I tried is to set a air tank to an initial pressure and let it vent to atmosphere through a nozzle while showing the exhaust plume using external analysis.  I can set the tank pressure with internal analysis using insert fluid subdomain with a lid at the nozzle, but if change it to external analysis and disable the lid in component control it redefines the whole computational domain as the fluid subdomain.

       

      I tried inserting a fluid body assembly created in check geometry into the tank volume but I can't get it to accept it as a fluid subdomain, I keep getting "Cannot find the faces associated with this item" error.

       

      I have been looking around for examples but haven't found any.

       

      Thanks.

        • Re: Fluid Subdomains with External Analysis
          Jared Conway

          fluid subdomains are completely enclosed

           

          you could try applying initial conditions to your fluid body

           

          but i think in the long run, this isn't going to be a good analysis for solidworks flow simulation. take a look at the suggested articles on the right and also the solidworks KB for filling/emptying analysis in flow.

           

          what exactly do you want to learn from the analysis?

            • Re: Fluid Subdomains with External Analysis
              Mike Peppard

              I finally got it to work after playing around a little bit more.  Just need to get the right sequence: Set analysis to internal, create fluid body assembly, insert fluid body assembly into volume it was created from, set analysis back to external, disable fluid body assembly in component control, rebuild project, then set initial conditions of fluid body assembly.   The step that I was missing before was rebuild project, Solidworks would not accept the component for initial condition settings until I did a rebuild.

               

              I am trying to reproduce a muzzle blast using data from interior barrel pressure and temperature measurements.  I have tried using different inlet time dependent sources of pressure and mass flow inside a small length of barrel to get the flow to choke at the exit.  When I ran the simulation trying the two different types of inlet sources the flow either stays supersonic in the barrel or the mass flow rates exiting the barrel didn’t work out.  So far setting the barrels volume to the initial conditions of pressure and temperature at the start and letting it “blow out” is giving the best results.

               

              I still have a problem where the mass flow rate of the gas exiting the barrel starts climbing gradually when the pressure is still decreasing at around half initial pressure which doesn't seem right.  I suspect that the gas temperature profile I am using is off a bit.