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Old   December 7, 2010, 13:09
Question natural convection Boundary Conditions
Saba Saeb
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Hello friends. I am trying to analyze natural convection from a 3D model in fluent. I face some problems. I don't know how should I determine boundary conditions for my model. Please help me. Here is the picture of my model. The solid part which is displayed by gray color is in constant temperature of 300 K and I want to analyze the meshed part which is air.

Thanks in advance,
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Old   December 12, 2010, 13:30
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The only boundary conditions you would have to specify (for the fluid) are at the top, bottom, and outward facing side. Are these walls? If not, and you're modeling open natural convection where you don't know what the velocity or pressures look like on these faces, then I'd suggest making a much larger fluid volume around the solid. The fluid can then enter the area of interest (inside the solid-bounded channel) without having to make too many assumptions about the inlet or outlet boundaries.

The fluid-solid interface should be thermally coupled by default, and thus you don't have to specify anything about it. I would suggest, however, that you refine the mesh a bit closer to the walls.

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Old   December 12, 2010, 19:41
Saba Saeb
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Dear CpmputerGuy,

Thank you very much for your resply. The volume of fluid ( air ) that I am going to analyze is restricted by solid walls and I don't need to investigate its effect on adjacent space. I devote my concentration on this part. I used pressure inlet for bottom, pressure outlet for top and a wall with zero heat flux ( adiabatic wall ) for front face and I used wall with constant temperature for all other walls. What is your opinion? I wonder if you could tell me more about interface and coupled.

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