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What are the BCs of this problem?(Problem with reversed flow or initialization)

    • Ivosp

      So I have a problem like this (actually it's 3D):

      The black box sucks the air in (with a fan) and transports it to the output, where it gets out. I am not interested of the simulation of the air inside the black box, I only want to simulate the air around it / infront of it. So I want to know, how the surrounding air is sucked inside the box. 

      I started learning fluid simulation only because of this, so I don't know alot and I am a beginner to this topic.

      I think I managed the BCs of the black box corret (all walls except the input/output areas where the mass flow leaves/enters the box). But I have struggle with the enclosure..

      First, I put the "sides" of the enclosure to wall and only the area infront and behinde the input/output to pressure inlet and pressure outlet. But then I get problems with reversed flow. I think the enclosure is big enough, but I'm not completly sure. It seems already huge to me.

      Then I thought it is more correct to put all the side of the enclosure to pressure inlet or pressure outlet, since the air is able to leave or enter the part of any side of the enclosure. If I try that, I get problems with the initialization and I can't run the simulation at all..

      Can anyone help me? 

    • Federico Alzamora Previtali
      Ansys Employee


      First, what is your enclosure physically? If you want to have fluid escape away from the black box, you may set the boundaries to Pressure Outlets.

      The warning messages about reverse flow simply means that:

      • flow is escaping a BC that is set to Inlet; or
      • flow is coming in through a BC that is set to outlet.

      Unless you have strict requirements that flow should only come in/out through those boundaries, this may not be a problem.

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