Rob
Ansys Employee

You can re-write the wall functions https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v222/en/flu_udf/flu_udf_ModelSpecificDEFINE.html%23flu_udf_sec_define_wall_functions ; source terms may also work. All I can advise (Ansys staff are limited in what we can say on here) is read the UDF manual having worked out what you need to alter.