Fluids

Fluids

Specifying turbulence intensity in Boundary Conditions

    • Dilini
      Subscriber

      Dear all,


      I did some reading regarding my question but still I am not 100% convinced. When we give values for the turbulence parameters in flow boundary conditions, how can I provide an accurate turbulence intensity that would suit my study?


      When I increase the turbulence intensity my results come closer to experimental study values. But I'm not sure if that is correct and since in that case it exceeds 20%. (I read that for most flows it is within 4-20 and intensities greater than 10 are considered high) My case of study is vehicle hydroplaning. Intensity measured data is not available for the free stream. 


      Please let me know.


      Thank you !!

    • Kalyan Goparaju
      Ansys Employee
      Hello
      Considering that your results are getting closer to experiment as you increase the turbulence intensity suggests that the experiments probably have a high level of velocity fluctuations. I strongly recommend checking other experiments at situations similar to yours to get a sense of the expected turbulence intensity

      Thanks Kalyan
    • DrAmine
      Ansys Employee
      Other point to review the velocity profile at inflow region
    • Dilini
      Subscriber

      Hello, 


      When my turbulent intensity value is around 100% I get a good agreement with experimental data. Is this intensity unlikely for a vehicle hydroplaning scenario fluid flow behavior?


      I do not have prior numerical analysis data to compare the intensities with. Please let me know.


       


      Thanks !!

    • DrAmine
      Ansys Employee

      Probably wrong profile of velocity or anything else: In a pipe flow and if you start doing  developed profile here one will see that Tu will decrease by increasing Reynolds Number and TVR start increasing with increasing Reynolds Number. It alls depends on upstream conditions which is your input. For external flow values of 5 to 10% are already very high.

    • DrAmine
      Ansys Employee

      and to finalize my comments here: it is easier to suppress excessive turbulent values rather to recover from low turbulence levels.

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