4 Replies Latest reply on Dec 15, 2016 11:02 AM by Siavash Khajehhasani

    Study on flow direction of air in a fluidic flip-flop

    Yong Jie Woon

      Hello, I'm new to Solidworks and I'm working on a project which I want to study on the flow direction of air inside a fluidic flip-flop. I have designed the flip-flop by myself using surface, knitting it and thicken it, the next thing I do is using flow simulation to study the flow but I have no idea how to continue for now. I have set the inlet flow, outlet pressure, and surface goals, but Im getting warnings like "Vortex appears" and "Supersonic flow exists", would appreciate so much for anyone who willing to teach me. Thank you.

        • Re: Study on flow direction of air in a fluidic flip-flop
          Varun Vohra


          It is working fine without any error or message. I am using SW 2017 SP.0.

          You can check your service pack if it is SP.01, upgrade to next one. May updating will solve it.


          • Re: Study on flow direction of air in a fluidic flip-flop
            Siavash Khajehhasani

            That's a good question!

            It is referring to the settings in the Calculation Control Options command under the Finish tab.

            The automatic stopping criteria for computational fluid dynamics is very difficult to set for the wide array of

            applications that use Flow Simulation. In this case the warning message is indicating that the Automatic stopping criteria may stop too earlier before the model may be converged. For example in the Calculation Control Options command you may want want to set the first item to “If all are satisfied”. Then under the Goals Criteria you can change the “Auto” to “Manual” and set their own value for the stopping criteria. This will force the number of iterations to increase and prevent the solver from stopping to early.



            Unfortunately this is a trial and error process. You can set a manual

            setting for the stopping criteria of a goal and then watch the convergence.

            If the converge history plot is relatively flat (value is not significantly changing)

            then you can manually stop the solver.

            In your case, I suggest to change the stop criteria to manual with percentage

            method instead of values (less headache).







            Considering the above steps, the convergence plot that you will get looks like the image below. Wherein, the vortex crosses pressure opening is gone since there is no recirculating flow at the outlets as the whole inlet flow exiting the outlet boundaries. The error of supersonic is still showing up, but you should disregard it as your solution is converged and now you know the cause of error. (see the image below).


            Further details regarding this issue can be found in S-048946.

            Besides, I have some other suggestions for your CFD analysis. Your grid resolution is basic and course, I would suggest to try more refined element espetially close to wall regions as you are dealing with turbulent flow. Furthermore, setting more goals for SW flow simulation is helping you to assure a full convergence (as long as they are used for convergence criteria). Typically users also set the global goals for pressure and velocity.

            Hope it helps.


            - Siavash