Im simulate natural convection, so I created computational domain (air) my solid body and Im wondering what boundary conditions are on free surfaces of this domain ? Are they isolated ( no heat and flow go out, or some special type of BC are there). Next questions is: do I need to model special mesh on solid-air surface (something like Inflation function in Ansys software to right simulate convection). Thank you for all answers and I hope you undersatnd my questions, Im new in flow simulation.