Learning Forum

[tungseng99]

Hi guys, I am trying to study the airflow pattern and temperature distribution within a greenhouse. Solar ray tracing with DO model is applied. There are velocity inlet and pressure outlet. The sidewalls and top wall of the external flow field are set as symmetry walls.

I have a question about setting the wall boundary condition of the ground around the greenhouse. I understand that if I have modeled the solid volume, then I don't have to put the wall thickness. And when the wall thickness is specified, there will be a thickness that grows away from the wall into the fluid. So, I'm a little bit confused and lost in this case whether do I need to put a wall thickness for the ground? Or do I actually need to model the solid volume of the ground?

It would be much appreciated if anyone could help me out with this.

Thank you in advance :)

[DrAmine]

You have actually two approaches: either you model the ground as solid so you resolve the thickness or you rely on modeling it through a couple of ways. One of them is just to provide thickness and to have sort of resistance normal to the wall.

[tungseng99]

Hi DrAmine Thanks for your reply!
I have another question is that I have a concrete floor inside the greenhouse with 10 cm thickness, I want to study the surface temperature distribution on the floor as well. Can I apply shell conduction on the floor?

[Rob]

You can. However, if you expect the thermal mass of the slab and soil to have an effect on the result you may want to include the slab as a solid and soil as a thin wall with a thickness.

[tungseng99]

Hi Rob, Thank you so much for your reply!
I have modeled the concrete floor and ground as solid volumes. I have a question about setting up the wall boundary condition.
I understand that the top surface of the ground that interacts with the air domain will be as coupled wall. But for the sidewalls and bottom surface of the ground, should I set them as adiabatic or constant temperature?
Besides that, I'm running a steady state simulation, do I need to patch different temperatures to both of the solid cell zones of the concrete floor and ground?

[Rob]

Adiabatic is probably OK for the sides of the solid, they should be far enough away from the area of interest to not do much to the solution. If the system is steady it'll reach the equilibrium result eventually, so while patching in values will speed this up they probably won't affect the outcome of the model.