Fluids

Fluids

wall function for temperature in FLUENT

    • tlcong
      Subscriber

      Hello.


       In FLUENT, when we use the wall function (such as Standard Wall Function), the wall functions for momentum, energy and species should be defined if these governing equations are solved. However, the way to define a set of customized wall functions is not specified in the Customization Manual (UDF Manual). In Chapter 2.3.48 (DEFINE_WALL_FUNCTION of Version 18.1), a piece of code for a wall function with linear and logarithmic lows is presented. In this code, the wall function indexes (wf_ret) are used to index the value to be defined. However, I still have some questions.


       1) How does the Fluent code judge if the regimes are laminar or turbulent? What is the critical value to separate these two regimes? Does Fluent use the same critical value for momentum and energy? For example, when we model the liquid metal, the linear sublayer for momentum is within Y-plus value of about 10 while the linear sublayer for energy is within Y-plus value of about 60. How can I define the wall functions of momentum and energy with different thickness of linear sublayer?


      2) Several wall function indexes are used in the code, including UPLUS_LAM, UPLUS_TRB, DUPLUS_LAM, DUPLUS_TRB, D2UPLUS_TRB, however, what are the indexes for energy and species equations?


       Thank you.

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