If you elect to export the results file, which contains the solution to the final timestep, the format will be:
filename.ext
where .ext is based on the format being written.
However, if you elect to export a different timestep, then the export file will have the following format:
filename_t#.ext
where # is the value of the timestep exported.
Note: EnSight transient files will be sequentially numbered, regardless of the
timestep value. For example, if timesteps of 1 s, 5 s, and 7 s
are exported, they will have the filenames
filename_t1.ext,
filename_t2.ext and
filename_t3.ext.