There exists a NORMAL particle in a GHOST cell. Particle may have gone OUT-OF-BOUNDS

MFiX
#1

Hello, everyone! I am getting the following error when simulating particle flow through a microchannel:
Error: There exists a NORMAL particle in a GHOST cell.
Particle may have gone OUT-OF-BOUNDS.
To resolve this issue, please consider:
a) Verify all wall boundary conditions are defined
b) Reducing the value of the variable NEIGHBOR_SEARCH_N (Solids>DEM>Max steps between neighbor search)
c) Increasing the particle and/or wall stiffness (Solids>DEM>Normal spring constant or Young’s modulus)
Current particle location (x, y, z coordinates):-0.1029E-01, 0.1239E-04, 0.3071E-03
Current particle velocity (u, v, w components) : -3684. , -0.2399 , -143.1

This error occurs when simulating up to 0.4s, I did try to increase the Normal spring constant of the particles to 1000, but I still get this error. I don’t understand what causes this error, here is my simulation case , I hope you can give me some advice, thanks!
0rcy_pl_un0.5_dem_vander.zip (237.3 KB)

#2

Hello everyone, 10 days have passed since I asked this question. During this time I have tried to reduce NEIGHBOR_SEARCH_N to 5, but after 0.8s of running I still get the following error：

Error: There exists a NORMAL particle in a GHOST cell.
Particle may have gone OUT-OF-BOUNDS.
To resolve this issue, please consider:
a) Verify all wall boundary conditions are defined
b) Reducing the value of the variable NEIGHBOR_SEARCH_N (Solids>DEM>Max steps between neighbor search)
c) Increasing the particle and/or wall stiffness (Solids>DEM>Normal spring constant or Young’s modulus)
Current particle location (x, y, z coordinates):-0.1500E-01, 0.1742E-04, 0.2151E-04
Current particle velocity (u, v, w components) : -332.7 , -8.901 , 10.31

T
0rcy_pl_50_new_constant1.zip (319.2 KB)
he particles that seem to be having problems are the ones at the inlet, here is my latest case, hopefully someone can point me in the right direction, I would appreciate it!

#3

The changes you made helped reduce the out of bound particle velocity by one order of magnitude. Please try

  1. Lower NEIGHBOR_SEARCH_N further, say to NEIGHBOR_SEARCH_N = 1
  2. Increase the spring stiffness (particle-particle and particle-wall) say kn=kn_w=10000
  3. Turn off cohesion
  4. Turn off your code modification
#4

Thank you very much for your reply Jeff! I’ve tried increasing Kn to 10000N/m, but it becomes extremely slow, it takes up to 30 days for 60 cores to run for 3 seconds, so I can’t predict if increasing normal spring constant will solve the problem either. neighbor_search_n decreases to 1, and the problem still occurs. I may not be able to ignore it because I’m studying particle deposition under van der Waals forces. Is it possible to solve this problem with the cohesion model activated?

#5

Another thing that strikes me as odd is that it is always the particles in the mass flow inlet that have this problem. Could this be caused by overlapping particles at the inlet? Any guidance you can give me would be greatly appreciated!

#6

DEM with 25 microns particles is going to run very slowly. I am suggesting to turn off cohesion and your modified code to rule out an issue with the cohesive force settings or your own code. This is only for troubleshooting.

How does the fluid velocity field look like when it fails?