Fluids

Fluids

How should one select y+ value for an open channel vof problem

    • prabu
      Subscriber

      Hello,


      How should one select Y+ value in meshing for a open channel problem.


      1. A video by Raef 

         Shows that y+ values kept well below 1 for a flat plate problem.


      however, in a literature "A three-dimensional flow model for different cross-section high-velocity channels" by abdulla, it is mentioned a range of 30


      Is there any rule of thumb for selecting a  Y+ values. 


      Thanks


      PRABU

    • DrAmine
      Ansys Employee

      If you want to resolve the viscous sublayer then you need to sick to yplus < 5 (Low-Re). If you do not want that you have to yplus>30 (High-Re). In that range the log-law of wall will be deployed to provide suitable  b.c' s at the wall. The linear profile in the vissoucs sublayer and  logarithm profile in the inner turbulent layer are not good in the buffer layer: The linear law would have 20% deviance from results there (buffer layer 5

      Actually Fluent provide for Epsilon and Omega based approaches an automatic wall treatment which would blend between both approach (low-Re and High-Re approach) based on cell wall distance or turbulent Reynolds Number.


       

    • raul.raghav
      Subscriber
      If you want more information regarding the y+ values and different near wall treatments, please refer to:

      https://forum.ansys.com/forums/topic/neat-wall-tratment/
    • prabu
      Subscriber

      Hello,


      Many thanks Amine and Rahul. 


      Thanks

    • DrAmine
      Ansys Employee

      You are welcome. If you think this issue is resolved please do not forget to mark it as such

    • José Mantovani
      Subscriber

       You can also use a y+ calculator in web, to calculate the y heigth of the cells adjacent to wall. In the link below, have a y+ calculator that make the calculations with the condition of you are using FLUENT.


      https://www.computationalfluiddynamics.com.au/tips-tricks-cfd-estimate-first-cell-height/


      Hugs,


      Mantovani. 

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