Fluids

Fluids

Liquid RGP file in FLUENT

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    • hsr200
      Subscriber

      Hi

       

      I am currently using FLUENT to analyze simple flow for various temperatures and pressure conditions.

      The fluid flowing inside the tube is aviation fuel that does not exist in the NIST database and is calculated at various temperatures and pressures, so the required physical properties were entered through the RGP file. (The temperature and pressure ranges are set to include liquid, gas, and supercritical conditions)

      The RGP file was made by referring to the format 12.7.1 Organization of an .rgp File in ANSYS CFX-Solver Modeling Guide (2021R2) and the Sample .rgp File in 12.7.1.2 and the required physical properties such as enthalpy, sound speed, and more, were calculated using fitting formulas from various sources.

      When calculated using this, the physical properties of the gaseous state were calculated as values of the gaseous state, but in the liquid state, they were calculated as values between the values of the saturated liquid and the saturated gas at that pressure.

      In order to observe the results of using other substances, the genRGP.py file was executed through CMD to generate the RGP file of water and to analyze it at the temperature and pressure of the liquid state. (The accuracy is set to 1e-3, the temperature and pressure ranges are set to include liquid, gas, and supercritical conditions) In this case, it was calculated as the properties for the liquid state I set.

      As such, I would like to know whether the original liquid state is not recognized well when the user creates the RGP file through manuals such as ANSYS CFX-Solver Modeling Guide.

      And if someone knew how to solve these problems, I would appreciate it if you could let me know.

       

      Thanks

    • DrAmine
      Ansys Employee

      If you compare the RGP tables: the one created with the Systemcoupling exectuable and the one you have: do you see any differences?

       

    • hsr200
      Subscriber

      Yes, I compared the RGP obtained by systemcoupling (The accuracy is set to 1e-3.)and one I have for water. (The temperature and pressure ranges are set to include the same liquid, gas, and supercritical states.)

      Since I made the RGP file without using the experimental or NIST database value, there was a difference from the RGP with systemcoupling executable in the value of each TABLE. (Especially, large differences are in an enthalpy(TABLE 1), entropy(TABLE 7) and saturation table(SAT_TABLE)).

      But the file formats were the same.

      So, does the value difference in each TABLE affect the calculation through the RGP file?

      Thanks.

    • DrAmine
      Ansys Employee

      Yes that will have an influence and affect the calculations.

       

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