9 Replies Latest reply on Jan 21, 2016 7:58 AM by Jet Lim

    Can I turn on a flow condition at a certain time step?

    Ed Hawkins

      I am currently running a flow simulation with a number of fluid sub-domains. One of these needs to be inactive until a particular time step is reached in the study, I have attempted to apply a time dependant control to the inlet and outlet boundary conditions (of the sub domain) but the simulation fails before the first interaction (as I set the volume flow to zero at zero seconds)

       

      I can't currently think of any way to effectively "turn on" the flow condition and sub domain at a time step. You can do with heat sources fairly easily - but this is a cooling liquid, so i need to understand the flow conditions of it, rather than just simulating it as a body with a heating (or cooling as it is in this case) condition.


      Any help greatly appreciated!

       

       


      Ed

        • Re: Can I turn on a flow condition at a certain time step?
          Amit Katz

          I don't think there is an easy way to do this, Ed. One thing I could think of is using a sliding mesh with a large wheel that has openings in it that will let the flow in once it reaches a certain angle. This could make your simulation take a long time, however, since it will be time-dependant with a fine temporal resolution.

            • Re: Can I turn on a flow condition at a certain time step?
              Ed Hawkins

              Amit,

              Thanks for the reply. The fluid subdomain does not turn on in the Simulation until 212minutes, and I am running for a total time period of 24 hours - with a view to extending to 1 week, so it may be that the time period is too long for this to be option. I will set it up and see what happens!

               

              Thanks, Ed

                • Re: Can I turn on a flow condition at a certain time step?
                  Amit Katz

                  Ed,

                  Could you elaborate on the concept a little bit? It seems to me that if you are running for so long you may as well just do a steady-state simulation. I am having a hard time imaging a practical flow scenario that requires 1-7 days to stabilize. At that time scale your iteration time step would be so large that a fluid mechanics approach becomes unfeasible. I could see it working for heat transfer in certain cases, but not fluid flow.

                    • Re: Can I turn on a flow condition at a certain time step?
                      Ed Hawkins

                      I have a fluid domain (oil) which is heating up at 2deg C every 2 minutes, until it hits 230C. It then needs to be monitored to review the heat soak into the solids surrounding it. This takes 24 hours in real life - so I am monitoring at 60 second increments and then saving results every hour. The second fluid domain is to form a barrier of cold to keep an area of the design cold. This only needs to start pumping once the main fluid domain hits 230C

                        • Re: Can I turn on a flow condition at a certain time step?
                          Amit Katz

                          So this is more of an oil bath? It seems to me that the small scale movements of the fluid in this application are not very important. There will be some natural convection but with such a slow burn it doesn't seem very important.

                           

                          What I would do in your case is just start the simulation with the hot oil already at a uniform 230C and have your cooling fluid be sprayed in at simulation time 0.

                  • Re: Can I turn on a flow condition at a certain time step?
                    Christopher Schaefer

                    Could you describe the system with a little more detail or even provide screenshots of the geometry/domains?  I agree with Amit that this sounds psuedo-steady state (my terminology).  Perhaps this can be approximated using the FE tools in SOLIDWORKS instead?  Are your fluid domains "moving?"

                    • Re: Can I turn on a flow condition at a certain time step?
                      James Riddell

                      Okay, take this with a HUGE block of salt, since I have never used this aspect of the program.

                       

                      Hypothetically, can you run the thermal portion until your fluid reaches 230 (with appropriate convection/conduction/radiation applied to the system) and then start a new analysis with the part, etc. at this end temp?  Just a thought.

                      • Re: Can I turn on a flow condition at a certain time step?
                        Julien Boissat

                        Ed, this is what I suggest:

                        1. Define a first project in which your domain is "inactive" as you said.
                        2. In the Finish conditions of the Calculation and Control Options, select when you want the first project to stop running. this could be a max physical time, or when a certain value of a goal is reached (for instance the average temperature of a Volume Goal defined on a disabled body that completely fills a particular cavity).
                        3. Run the project
                        4. Clone the project (without results)
                        5. Modify the project to activate whatever you want.
                        6. In the Initial and Ambient Conditions of the General Settings, select the type as Transferred instead of User-Defined.
                        7. Select the result file of your first project. This will allow you to continue where your first project finished, and with different boundary conditions.

                         

                        Julien