[panos_metal]

Hello

I am simulating the downward flow of air in a vertical tube with heated walls of constant temperature. The air is injected (air temperature at the inlet-25 C)from the top by 6 little holes in the direction of gravity ..Reynolds number on the injections exceeds 2100 so the flow assumed turbulent..BUT the diameter of the tube is much higher and when i calculated the Re number at the main tube Re does not exceed 200..That means that in my domain i have for sure a region of turbulent (the upper part where the air is injected - the phenomeno is endured due to the expansion of air as i have take the air density as temperature dependent) and a laminar region ( flow in the main cylinder). Can someone help me on the choice of a model? The only exit of the furnace is at the bottom.
I have searched a lot in bibliography but i havent found something similar.
Can you please advice me how i have to treat the problem in terms of the appropriate model?
Please help
Thank you in advance