DEM："Particle Count Mismatch in DEM: Boundary Conditions vs. Simulation Results"

MFiX
1

I am simulating a 3D CFB riser (dimensions: 0.077 × 1.071 × 0.077 m) using MFIX-21.1.4 with the following setup:

Particles injected at the bottom via MASS_INFLOW boundary condition:

mass_flow_rate = 0.35 kg/s

Particle diameter = 0.00085 m, density = 2500 kg/m³

Top boundary: Open (particles escape freely).

Expected vs. Actual Behavior:
MFIX GUI reports injection rate:

Particles injected per solids time step = 9.29191225E-01

Particles injected per second = 373,186

After 1 second of simulation(0~1s):

Total particles in the system: 795,117

So, Why is the actual particle count (~795k) much higher than injected (~373k/sec) ?

This is a circulating fluidized bed (CFB) riser, so particles should:

  1. Enter from the bottom.
  2. Be carried upward by gas flow.
  3. Exit from the top (to a cyclone or return loop).
    By the way,I am using the MFIX-21.1.4 in a linux system.
2

Can you try with the latest version (25.1)? Troubleshooting on 21.1 may not be worth it. I am assuming you don’t have any particles in the system at the beginning of the simulation.

3

Thank you! I will try later.