Two particle problems in DEM

MFiX
#1

Hello, everyone. I met two problems about particles in DEM simulations, such as 3.6. Three Dimensional DEM Hopper — MFiX 21.3 documentation. My panel settings are basically consistent with those in toturial 3.6.

(1) The diameters of the lower cylinder and the particles are respectively 15mm and 3mm. Namely, d_cylinder/d_particle=5. However, as can be seen from the following figure, the diameter of lower cylinder only nearly 3 times larger than that of particles in the VTK, instead of 5 times. I am confused about this.
image

My case file is Hopper_3D_DEM.mfx (17.1 KB)

(2) In some cases, individual particles are unexpectedly outside the domain during the iteration (see the attached figure below). What cause this nonphysical phenomenon? How to overcome this problem?

image
image999×566 85.9 KB

#2
  1. You are not saving the particle diameter in the vtp file so the scaling is off. Make sure you add the particle diameter to the list of variables in the vtp file, then the GUI will display the particles at the correct scale.
  2. The particles are probably too soft. Increase the spring stiffness (kn and kn_w) to see if it helps.
Particles escaping the domain
#4

Thank you. I will have a try.