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15.16.3 Starting a Non-Premixed Calculation From a Previous Case File

You can read a previously defined FLUENT case file as a starting point for your non-premixed combustion modeling. If this case file contains inputs that are incompatible with the current non-premixed combustion model, FLUENT will alert you when the non-premixed model is turned on and it will turn off those incompatible models. For example, if the case file includes species that differ from those included in the PDF file created by FLUENT, these species will be disabled. If the case file contains property descriptions that conflict with the property data in the chemical database, these property inputs will be ignored.

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PDF files created by prePDF 2 or older are not supported by this version of FLUENT. The files generated by PrePDF version 3 or newer, are fully compatible.

In the Species Model panel, select Non-Premixed Combustion under the Model heading. When you click OK in the Species Model panel, a Select File dialog box will immediately appear, prompting you for the name of the PDF file containing the look-up tables created in a previous FLUENT session. (The PDF file is the file you saved using the File/Write/PDF... menu item after computing the look-up tables.) FLUENT will indicate that it has successfully read the specified PDF file:

Reading "/home/mydirectory/adiabatic.pdf"...
read 5 species (binary c, adiabatic fluent)
pdf file successfully read.
Done.

After you read in the PDF file, FLUENT will inform you that some material properties have changed. You can accept this information; you will be updating properties later on.

You can read in an altered PDF file at any time by using the File/Read/PDF... menu item.

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Recall that the non-premixed combustion model is available only when you used the pressure-based solver; it cannot be used with the density-based solvers. Also, the non-premixed combustion model is available only when turbulence modeling is active.

If you are modeling a non-adiabatic system and you wish to include the effects of compressibility, re-open the Species Model panel (Figure  15.16.1) and turn on Compressibility Effects under PDF Options. This option tells FLUENT to update the density according to Equation  15.7-1. When the non-premixed combustion model is active, you can enable compressibility effects only in the Species Model panel. For other models, you will specify compressible flow ( ideal-gas, boussinesq, etc.) in the Materials panel. See Sections  15.7.2 and 15.16.4 for more information about compressibility effects.

Figure 15.16.1: The Species Model Panel With Available PDF Options
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Retrieving the PDF File During Case File Reads


The PDF filename is specified to FLUENT only once. Thereafter, the filename is stored in your FLUENT case file and the PDF file will be automatically read into FLUENT whenever the case file is read. FLUENT will remind you that it is reading the PDF file after it finishes reading the rest of the case file by reporting its progress in the text (console) window.

Note that the PDF filename stored in your case file may not contain the full name of the directory in which the PDF file exists. The full directory name will be stored in the case file only if you initially read the PDF file through the GUI (or if you typed in the directory name along with the filename when using the text interface). In the event that the full directory name is absent, the automatic reading of the PDF file may fail (since FLUENT does not know which directory to look in for the file), and you will need to manually specify the PDF file. The safest approaches are to use the GUI when you first read the PDF file or to supply the full directory name when using the text interface.


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Next: 15.16.4 Solving the Flow
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