You can read NASTRAN Bulkdata files into FLUENT with the File/Import/NASTRAN/Bulkdata File... menu item.
File Import NASTRAN Bulkdata File...
When you select the Bulkdata File... menu item, the Select File dialog box will appear and you will specify the name of the NASTRAN File to be read. This file will have .nas, .dat, .bdf file extensions. The solver reads grid information from the NASTRAN file. For information about importing NASTRAN files, see Section 6.3.7.
To import NASTRAN Op2 files into FLUENT use the File/Import/NASTRAN/Op2 File... menu item.
File Import NASTRAN Op2 File...
In the Select File dialog box, specify the name of the NASTRAN Output2 File to be read. This file is an output binary data file that contains data used in the NASTRAN finite element program. This file will have .op2 file extension.