Fluids

Fluids

constants of eddy viscosity transport in CFX

    • hamda
      Subscriber

      Hi,
      I want to specify the constants for EVT model but I don't know for example what is C1 in CFX? there are five constants; C1, C2, C3, A+,

      but in CFX I couldn't find such constants. I read tutorial and found nothing about that and will really appreciate if somebody helps me on this issue.

      Many thanks

    • DrAmine
      Ansys Employee

      The constants are not exposed. You need to increment them in CCL by adding the Singleton VISKTRB COEFFICIENTS in the Turbulence Model part of the CCL. Only C1, C2 and C3 are accessible.


       


      VISKTRB COEFFICIENTS:


      C1 Coefficient = your value


      END


       


      We do not recommend the usage of two-equation RANS approach for a daily engineering task

    • hamda
      Subscriber

      Dear Abenhadj,


      Thanks. My project is an academic one and I have to use EVT model . I have read some papers related to my project and one of them used CFX14.5 and used EVT model and specified all constants for it . But you say only C1, C2, C3 are accessible. I am confused!


      Can I define all of them in CEL?


      Thanks

    • DrAmine
      Ansys Employee

      Yes. You need to adjust the CCL as they are not exposed in the GUI.

    • hamda
      Subscriber

      Thanks,


      I am pretty new in CFX . Is CEL like UDF in fluent? and should be written in visual C++? following command is a CEL?


      VISKTRB COEFFICIENTS:


      C1 Coefficient = your value


      END


      Many thanks


       


       

    • DrAmine
      Ansys Employee

      No. CFX Expression Language (CEL) is an interpreted, declarative language that has been developed to enable CFX users to enhance their simulations without recourse to writing and linking separate external Fortran routines.


      The snipet you hulight is a CCL snippet: CCL is CFX Command Language. It is a simple language that can be used to create objects or perform actions in the post-processor


      Please check the help and carry out some tutorial to get familiarized with CFX.

    • hamda
      Subscriber

      I know expression, I wrote expression before in CFX. But you use "End" in your CEL  and made me confused since I never used it in my CEL. I just defined a formula and equation for a parameter without end.


       


      Thanks

    • DrAmine
      Ansys Employee

      You need that END because it is the END of the SINGLETON

    • DrAmine
      Ansys Employee

      Moving this to Fluids related thread

    • rgfsteed
      Ansys Employee

      Hi Hamda,


      The constants are in fact exposed in the GUI but out of sight, but not hidden. We do this for advanced options so users don't feel they need to enter values or override defaults.


      Under the Turbulence options in the Fluids Models tab, look for "Advanced Turbulence Control" and click on the + at the far right to expose advanced settings. 



       


      Section 13.4.2: Fluids Models Tab of the CFX Pre User's Guide will provide you with additional information about this panel and links to the relevant portion of the CFX Theory Guide. You'll need to review this to understand which inputs correspond to your coefficients.


      Regarding CEL and CCL, CEL is the expression language (i.e. algebraic expressions), whereas CCL is the CFX Command Language. The acronyms are dangerously close and are often confused. The command language, CCL, is an object definition language used to define object states, not a programming language. CFX will also interpret Perl commands when reading CCL, allowing program control. You'll find more information about this in the CFX Reference Guide > Chapter 13: CFX Command Language


      Best regards,
      Robin

    • DrAmine
      Ansys Employee

      The coefficient of interest for viscosity transport model are not exposed in GUI.

    • hamda
      Subscriber

      Dear Robin,


      Thanks for wonderful information.  But as abenhadj


      said : The coefficient of interest for "viscosity transport model" are not exposed in GUI.


      At any rate your information was helpful to me.


      Many thanks


      Hamda


       

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