Some confusion about the official tutorial case 3.5: 3D fluidized bed

MFiX
1

Hello, colleagues.I am new to CFD and I am trying to run tutorial 3.5, 3D fluidized bed(DEM), but I have encountered some confusion.
I successfully ran this case according to the settings in the tutorial, but after trying to reduce the solid diameter from 0.005 in the case to 0.004, I found that the solid particles were basically not fluidized. Of course, increasing the fluid inlet velocity significantly can continue to fluidized the solid, but is this normal? Is the influence of particle diameter so significant?I only changed the solid diameter, everything else is consistent with the settings in the tutorial
TEST.mfx (11.5 KB)

diameter 0.005m
diameter 0.005m1158×908 101 KB
diameter 0.004m
diameter 0.004m1158×908 79 KB

2

Hi guys, has anyone noticed my problem? Does this mean that the grid size in the tutorial is not the right size?

3

The case with particle diameter of 5mm appears to miss collisions, which creates the illusion it is fluidized. Please try with a DES grid of 10x30x10 (go to the solids>DEM pane), and increase the inlet velocity, say around 3m/s.

image
image1238×754 136 KB