[jabecker]

Hello Fellow Foamers,

I am in need of some help. I am wanting to investigate the heat conduction in a steady-state open system, specifically within a nanosized vertical cylinder.

My Case:

• Cylinder filled with air that has a radius of 2 micrometers and a height of 200 micrometers.
• There is a continuously heated bottom plate at 573K
• Initially the rest of the cylinder starts at room temperature, set at 298K
• Assume adiabatic cylinder walls, so it is set to zeroGradient
• I want a constant pressure in the system, so I set the top, bottom and side walls to a fixedValue of 1e5

In order to maintain a constant pressure with an increase in temperature, there must be an increase in volume. This is why I want to create an open system. The trouble I am having is in determining the initial boundary conditions that should be used for the temperature at the top of the cylinder and for the velocity of all of the walls. I think they need to be of type: calculated, but I am not sure how this boundary condition really works. I am running the program in buoyantSimpleFoam.

Any guidance would be much appreciated

Thank you in advance,
Jen

[fabian_roesler]

Hi Jen

Why do you use the compressible buoyantSimpleFoam? You could use the incompressible Boussinesq buoyant solver. There you don't have any problems with the pressure in your system as you just change the density in the gravity source term. With this solver you can have a closed system without volume change. Have a look at the tutorial. I am pretty sure you can use the total case except the geometry. It is a rectangular room heated from below.

Regards

Fabian