Fluids

Fluids

Transient and Steady state simulation results

    • Nicolo
      Subscriber

      Hi


       


       I have performed a two phase flow simulation both in transient and steady state. 


      Once I run it in transient apparently there is no problem  and I can see the flow regime is kind of a plug flow with a lot of up and down, but once I try the steady state simulation the residuals don't reduce and it does not look like it is converging (I have attached the picture).


      Does it mean that my transient simulation is wrong ?

    • Rob
      Ansys Employee

      Steady state solver will try and find the single solution to the problem, if there are any transient features in the flow it'll struggle to converge, and typically give a residual plot like you see. However, the scale of error may be small enough that you can ignore it. 


      The transient solver will pick up and include all of the small changes if the time step is correct. These changes may be small enough that you don't really notice them, but the changes may be sufficient that there isn't a steady solution. 


      Have a look in the tutorials for monitor points: we use those to help understand if a solution is converged. 

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