April 20, 2023 at 10:59 am
Rob
Ansys Employee

You're looping over cell and face threads, so I'd start here  https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v231/en/flu_udf/flu_udf_ChapParallelUDFUsage.html   Note, we can't give much advice on UDFs.