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Does the RNG k-e model include the turbulent diffusivity?

    • LukeM
      Subscriber
      I'm working with the RNG k-e model in my mass transfer simulations, and in my simulation it seems like the model does not include a turbulent diffusivity and/or turbulent Schmidt number. The viscous model and species model boxes never mention a turbulent Schmidt number, only the molecular diffusivity. Based on that assumption, I ran simulations with a UDF defining the diffusivity, including both molecular and turbulent diffusivities. nHowever, I recently found an article in the User's Guide (4.3.7. Convective Heat and Mass Transfer Modeling in the k-e Models) suggesting the turbulent diffusivity is automatically included and can't be changed. So did my previous simulations account for the turbulent diffusivity twice? nI'm using Fluent 19.2. Thanks in advance. n
    • DrAmine
      Ansys Employee
      The turbulent Schmidt Number can be changed for single phase flows via UDF https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v202/en/flu_udf/flu_udf_sec_define_turb_schmidt.html?q=Schmidtn
    • LukeM
      Subscriber
      I conducted multiphase simulations. For clarification, I'm asking about the default turbulent Schmidt number settings when using the RNG k-e turbulence model, not about changing the value. n
    • DrAmine
      Ansys Employee
      Is still not clear what you are asking: For RNG it is written that it is similar to the calculation for heat transport with alpha_0=1/Sc with Sc is the laminar Schmidt Number.n
    • LukeM
      Subscriber
      I'm asking if, by default, the RNG k-e model includes a turbulent diffusivity for mass transfer simulations. n
    • Rob
      Ansys Employee
      Mass transfer as in convection or as in between phases (eg boiling)? n
    • LukeM
      Subscriber
      As in convectionn
    • DrAmine
      Ansys Employee
      Yes it has as all other turbulence models: turb diffusivity is required for energy, species, sclars, etc..n
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