Hi,
I would like to model an airflow through sand. Any ideas of how to model the sand or any irregular, high porosity structure?
Typically we would model this using a distributed resistance and then assigning some Permeability to that volume. Note we will not show that the sand will move but rather assume a fixed shape
I tried by by modeling a volume of sand with assigned air ratio of 0.05 in all directions and constant conductivity of 0.71 W/m2K. The sand is surrounded from all sides by a fluid (air) while the least fluid thickness is 5mm. Unfortunately the simulation does not converge.
Does the resistance have a good uniform mesh applied to it? 4-5 elements as a minimum through the thickness?
How about the rest of the model, what is the overall setup?
Thanks,
Jon
I have attached the simulation fille.
Setup:
Air is blown through the pipe on the top at 30l/min in a cylindrical container. There is a heater at the bottom of the cylinder with heat release rate of 100W. The cylinder is filled with sand. All surfaces are exposed to the environment with ambient temperature of 20C and convection coefficient of 5W/m2 K. I am interested in the air flow and thermal distribution through the cylinder.
So far I did a successfully simulation without the sand, but with the sand volume modelled as resistance material it does not converge. Ideally I want the sand to be as much close to the cylinder walls as possible, although I understand that the resistance volume has to be surrounded by a fluid from all sides.
Please could you share a CFZ file?
Your setup sounds about right though 🙂
We do not have to have a fluid on all walls of a resistance, although you do need a fluid or solid.
Here is the CFZ file and a few pictures of the setup.
A few comments which I think will leave this running OK:
Hope that helps.
Jon
Thank you Jon for the suggestions!
I tried forced flow without gravity and with sand touching the walls, but the solution still does not converge 😞
Yavor
Could you share the CFZ again please? I think it might need a longer outlet as there may be recirculation over the boundary condition, happy to test it here.
Here you are. So far I have successfully run simulations without the presence of the sand under both forced and natural convection settings. They both give sensible results and suggest possible circulation in the region of the outlet.
Thank you!
To get around the recirculation issue, can you extend the outlet air? Try 5x diameter in length at least.
I would set your resistance flow direction to z, as that is the main flow direction and try again.
Also use Advection Scheme 5.