How to reduce particle porosity?

Why do the purple bed particles in my fluidized bed model have such a large void fraction, resulting in a high initial bed? How can I adjust the void fraction of the particles to make the bed height lower?
Looking forward to any possible answers, thanks!

combustionCase.mfx (15.2 KB)

I’d also like to ask how I can set it up so that the bed particles don’t fall.

You have set a spacing of 0.6 (i.e. 60% of particle diameter) between particles in the IC region. You can reduce the spacing (say 0.01) and you will get a lower initial bed height. The may be harder to converge since it will be more packed.

I don’t understand the second question “set it up so that the bed particles don’t fall”. Please elaborate.