Fluids

Fluids

k-epsilon vs SST k-omega

    • amirmohammad.rajabi
      Subscriber

      Hello, 

      I am trying to simulate water flow through a pipe with horizontal and vertical inlets. Basically, the water flows through the pipe and hits an end wall and eventually goes through the outlet. Choosing the right turbulence model has become a bit of a delimma for me since I get different results depending on which model I use. Based on what I have read, SST k-omega model seems to better fit internal flow and flows that deal with fluid-wall interaction. I would like to know the insight of the community that has more experience with these models. Is the SST k-omega the better choice in this case?

      I have also attached a photo of the geometry.

    • Rob
      Ansys Employee

      Images of the results will help. Along with convergence plots.  I also suggest replying to answers when they're given: opening a second thread tends to annoy us more than it helps you get an answer. 

      In terms of the models. I'd expect near enough the same result for SST and k-e if you use the enhanced wall treatment and converge both. This assumes the mesh is adequate. 

      • amirmohammad.rajabi
        Subscriber

        Hello Robert,

        Thank you for your answers and apologies for the annoyance.

        It seems like the k-omega method converges better than the k-epsilon method.

        I also have another question, I want to measure the time that the flow spends within the tube before it gets out. I know that I have to do a transient simulation but is there a way measure the time it takes for the water particles to get out?

    • amirmohammad.rajabi
      Subscriber

      Hello Robert,

      Thank you for your answers and sorry for the annoyance.

      It seems like the k-omega method converges better than the k-epsilon method.

      I just have another question, I want to measure the time that the flow spends within the tube before it gets out. I know that I have to do a transient simulation but is there a way measure the time it takes for the water particles to get out?

    • Rob
      Ansys Employee

      Pathlines will show you the residence time for the bulk (moving flow).  There's also a way to use a combination of scalars and source terms but I can't explain futher on here. If your supervisor has access to the Customer Portal ask them to look up "mean age of air". 

      • amirmohammad.rajabi
        Subscriber

        Thank you for your answer Robert.

        Could using DPM also help with finding the residence time of the particles to estimate the time it takes for particles to travel through the pipe?

    • DrAmine
      Ansys Employee

      Yes mass less particle tracking can help getting the residence time in the domain.

      • amirmohammad.rajabi
        Subscriber

        Thank you for your reply Amine.

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