Fluids

Fluids

Why is my velocity so much higher at the end pipe in the system?

    • thaipham0815
      Subscriber

      I was running a 2D simulation and I am wondering why the velocity at the outlet is so much higher than the inlet. I know that it is impossible, but what in ansys might be causing this issue. I will include the simulation conditions below. If there is something else that I did not include, it mostlikely means that I did not mess with those settings. 

      Solver: Transient, Pressure Based
          Number of Time Steps: 600
          Time Step Size: 1s
          Max Iterations/Time Steps: 20

      Model: Viscous(Laminar)
      Fluid material: Water-Liquid
      Method: Simple
      Initialization: Hybrid
      Mesh cell size: 0.0005m
      Nodes: 260053
      Elements: 258440

      Boundary Conditions: 
      Inlet velocity = 0.115 m/s
      Wall = No Slip
      Outlet Gauge Pressure = 0 Pa

      As you can see, the outlet is 0.19 whereas the inlet is only 0.115. If anyone has any information on this, please let me know. Thank you!

    • DrAmine
      Ansys Employee

      Is the case converged? 

      Can you assess the Mass Flow at inlet / outlet and check the overall mass imbalance.

      You have recirculating flows in both cavitities and so I won't rely much on velocity at the outlet but rather if the whole system is conserved! (Check if you have at the outlet reversal flow.. I aslo see large blue regions there telling me that not the whole outlet region is "feeling" the inflow... which is to be expected giving the flow bubbles/separations/reattachements you have).

      • thaipham0815
        Subscriber

        What corrective actions would I go about to fix this issue. I have tried looking through a couple theory books and could not figure it out. As you can probably tell, I am very new to ansys..

    • DrAmine
      Ansys Employee

      Why do you think you require corrective actions? Just ensure you are converging deep and using proper BC's and Turbulence Modelling. If you have strong reversal flow at outlet try to place it bit flow downwards.

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