Hi.I'm trying to run the flow driven by buoyancy in a vertical two-side open pipe heated from outside. The pipe is in the air, which is otherwise still. Can somebody, please, help me with defining the inlet and outlet boundary conditions. Should they be pressure inlet and outlet and gage pressure set to zero in both? What about using the specified operating density? How to calculate the inlet (down end) and the outlet (upper end) pressure? Thank you very much.

1) You need to create a UDF which will change the density based on boiling parameters (temperature and pressure)

2) Use 2 phase mixture (cavitation model) 3) inlet and outlet pressure may be equal if the flow is gravity driven 4) check the gravity direction and initialisation steps are important mail me if you need any more help sachcool80@gmail.com

THis is straightforward. Use inlet and outlet pressure boundaries with the gauge pressure = 0. Make sure to specify a proper backflow temperature for the outlet. FLUENT will determine the air column height effect automatically. The specified operating density, if you go that route, would typically be set as the density at the inlet.

Thanks. This is bsically what I've tried to do but the convergence was not good. Thanks again