Each type of file read or written in FLUENT has a default file suffix associated with it. When you specify the first part of the filename (the prefix) for the commonly used files, the solver automatically appends or detects the appropriate suffix. For example, to write a case file named myfile.cas, just specify the prefix myfile in the Select File dialog box (Figure 4.1.1) and .cas is automatically appended. Similarly, to read the case file named myfile.cas into the solver, you can just specify myfile and FLUENT automatically searches for a file of that name with the suffix .cas.
The default file suffix for case and data files, PDF (Probability Density Function) files, DTRM ray files, profiles, scheme files, journal files, etc., are automatically detected and appended. The appropriate default file suffix appears in the Select File dialog box for each type of file.