I assume you mean this one? https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v231/en/flu_udf/flu_udf_sec_using_udfs_parallel.html%23flu_udf_sec_parallel_example It looks to be applied to a face, but I'd not recommend using an interior without adding some further checks that are also outlined in the manual.
The examples are there to show how to take various serial concepts (typically face and cell loops) and ensure they're run correctly in parallel. There are no example geometries as the UDF features are fairly advanced.
You are navigating away from the AIS Discovery experience