Fluids

Fluids

Reverse flow physical or numerical

    • Shuttle
      Subscriber

      Hello, 

      I am currently simulating a gap between the rotor and stator with eccentricity in Fluent and I am getting a reverse flow at the outlet. I want to know if the reverse flow is created as a numerical error or if is it a physical problem?

    • Nikhil Narale
      Ansys Employee

      Hello,

      Are you using pressure outlet boundary condition? In that case, flow reversal generally happens due to flow separation/recirculation close to the outlet boundary. The pressure outlet condition is not physical, if this region of separation/recirculation is in close proximity to the exit. You can try extending the outlet boundary. Else, try using outflow or mass flow outlet boundary condition, but be cautious while using these conditions.

       

    • Shuttle
      Subscriber

      Hello,

      Yes, I am using a pressure outlet as outlet boundary condition. I do have extended my outlet after reading through forums, but reversed flow still exists. It has reduced a lot from 28% to 7%, do you think extending more will get rid of reverse flow? until now I ran simulations up to 4000 iterations, thought if it might get away. I can't use another boundary condition, as I am building a model based on a research paper. 

    • Rob
      Ansys Employee

      Have a look at the flow field to understand what's happening. That'll then tell you if the backflow is a problem: if it's getting back to somewhere interesting then it's a problem! 

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