Fluids

Fluids

Can too small Yplus be a problem when using the enhanced wall treatment?

    • neurochall
      Subscriber

      When using the RNG k-epsilon model, I use the enhanced wall treatment to simulate low-Reynolds flows.


      However, because the hydraulic diameter varies according to the flow path, on some area of walls, the Yplus value is much lower than 1, even 0.01.


      Can this cause physical errors as well as slower convergences when I want to solve momentum, turbulent, and energy equations?


       


       


       

    • DrAmine
      Ansys Employee
      It's always advised to have 10 to 15 cells across the boundary layer. It's not only a matter of yplus.
    • neurochall
      Subscriber

      Thank you for your kind answer.


      If I put more than 10 to 15 cells across the boundary layer and the Yplus near the wall is much lower than 1, is it ok?

    • Keyur Kanade
      Ansys Employee
    • DrAmine
      Ansys Employee

      Yes. That is okay: but this is not always possible because one should never use large cell volume jump normal to the wall across the boundary layer. By the way I recommend using SST Model: that is the current industry standard..

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