Have a look here https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v231/en/flu_ug/flu_ug_bcs_sec_operating.html%23flu_ug_uns_sec_boussinesq If you set beta as zero, or near enough zero it's going to cause you a problem. You need to find the correct value for the fuel.
You are navigating away from the AIS Discovery experience