Learning Forum

[Calvin]

Hello,

I am using Fluent version 2024 R1 on Linux. Part of my simulation set-up includes importing thermodynamic data for a non-premixed combustion case. When using the standard two temperature ranges, everything works fine (no trouble importing, simulation starts, begins solving, etc.) 
However: for some of my species I would like to specify thermodynamic data over 3 temperature ranges. I followed the documentation for Chemkin format to change thermodynamic data to accomodate more than 2 temperature ranges. For example:

Before:

O2                121386O   2               G   200.00   3500.00   1000.00     1
 3.28253784E+00 1.48308754E-03-7.57966669E-07 2.09470555E-10-2.16717794E-14    2
-1.08845772E+03 5.45323129E+00 3.78245636E+00-2.99673416E-03 9.84730201E-06    3
-9.68129509E-09 3.24372837E-12-1.06394356E+03 3.65767573E+00 8.68010400E+03    4

After:

O2                121386O   2               G   200.00   3500.00               1
TEMP   200.00 1000.00 2500.00 3500.00
0.30563941E+01 0.89059362E-03-0.20849917E-06 0.24115927E-10-0.10516720E-14
0.37260112E+04 0.44780081E+01
0.34298433E+01-0.25250392E-03 0.80470663E-06-0.33336490E-09 0.43425671E-13
0.37097800E+04 0.26751302E+01
0.37695923E+01-0.59256858E-03-0.21359336E-06 0.13644331E-08-0.63575666E-12
0.35908836E+04 0.78130486E+00

When I try to import this, I get errors like "Invalid THERMO data at line no. 108." 

I tried to research the problem before posting here. It turns out I have the same questions as some previous posters:

• Here the response was that the capability would be added to a version in late 2019:
  • https://innovationspace.ansys.com/forum/forums/topic/how-to-add-a-third-temperature-range-in-chemkin-thermo-file/
• Here the response was just that "The problem has been resolved"
  • https://innovationspace.ansys.com/forum/forums/topic/how-to-use-more-than-two-temperature-ranges-of-chemkin-thermodynamic-data-in-fluent/

The strange thing is -- I recall being able to use this thermodynamic file format in an earlier Fluent version... Was the capability removed in 2024 R1 for some reason? Or, more likely, have I done something wrong in my implementation somewhere this time around?

Thanks!
Calvin 😊

[jcooper]

Hi:

I believe the 3 temperature ranges are only supported by the NASA-9 thermo format. So, in your thermo file, you would have one block of data between THERMO NASA9 ... END, and another with the regular format data THERMO ... END.  There is a sample of this thermo format in ...ANSYS Inc\v242\reaction\data.  Below is the link to the NASA document that describes this format and includes a sample in the appendix.

https://ntrs.nasa.gov/api/citations/20020085330/downloads/20020085330.pdf