Buoyancy turbulence

Atit

I was wondering about 'Buoyancy turbulence' option in CFX-Pre. The driving mechanism of my simulating flow is natural convection. When simulate as the laminar flow, the Reynolds number suggests to switch to turbulent instead. So I will use k-e model in CFX to find the solution. Anyway I have the problem with 'Buoyancy turbulence' option. I do believe that I have to use this option, but I am not sure if 'Production' or 'Production and Dissipation' is the suitable one. Can someone explain the difference between these two options to me?

Thank you for your consideration.

Atit