How to establish a DEM packed bed model with an empty tube development section at the bottom

Hi, everyone! I want to establish a packed bed model with an empty tube development section at the bottom, It can be described like the black region is the whole background, and particles generated in the blue region(bed region), and the particle is invisible for the slice, so I can have the empty region for the gas to go through(red region), Can MFiX do it?
Thanks for your reply!

particle_input.mfx (12.6 KB)

You can put an internal surface between the red and blue region. This will prevent particles from going down below the internal surface and let them pack in the blue region. The gas phase can go through the internal surface.

Thanks, jeff! How should I set the internal surface in the < region > and define the border?

Hi, jeff. I found the IS in the GUI, and I wonder know what’s the difference between Impermeable
and Semi-Impermeable, it seems that Impermeable IS means gas and solids can not go through and Semi-Impermeable means gas can go through and solids can’t. and what’s the meaning of < Fluid permeability >, < Internal resistance coefficient >, How should we set it when needed?

This is covered in the MFiX manual here: 8.3.11. Internal Surface — MFiX 22.1 documentation