It's the local velocity, so velocity magnitude that's used. You may also want to account for solar gain (heating) as that's a significant part of comfort.
Yes, there is a UDF, but as you'll know from reading the rules when you signed up I (as Ansys staff) can't share it on here. You may want to have a look on the Customer Portal; students may not have access but staff may if your site has a maintained licence.
You are navigating away from the AIS Discovery experience