That is the solution, hence my first post in the thread. Look at https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v231/en/flu_ug/flu_ug_bcs_sec_operating.html specifically 7.3.1.5 You're setting rho-rho0 to be zero, so lose the gravity term for the exterior boundaries, otherwise you need to set a pressure gradient on the exterior boundary to account for (rho-rho0)gh and that gets messy.
You are navigating away from the AIS Discovery experience