Tip of the Month 25.10 - Writing particle plot files for subregions in MFIX-Exa

MFIX-Exa Announcements
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MFIX-Exa allows you to write plot files for specific subregions of the domain and filter particle data by phase (type). This can help reduce file size and focus analysis on areas of interest.

:compass: How to Use It

  1. Define regions that cover the areas of your system where you want to capture particle data.
  2. Specify solids regions to identify which particle types to include and how frequently to save the data.

:warning: Limitations

  • Currently, particle filtering is limited to type (phase) only.
  • While fluid data can be included, it is not region-aware and will be saved for the entire domain.

:test_tube: Example: Two Particle Sizes

Let’s walk through an example setup for a system with two particle sizes (solid0 and solid1).

:small_blue_diamond: Define Regions

In this example, we extract particle data from:

  • The left half of the domain
  • The right half
  • A middle section
mfix.regions = full-domain  west-half  east-half  middle

regions.full-domain.lo  =  0.000   0.000   0.000
regions.full-domain.hi  =  0.150   0.750   0.015

regions.west-half.lo    =  0.000   0.000   0.000
regions.west-half.hi    =  0.075   0.750   0.015

regions.east-half.lo    =  0.075   0.000   0.000
regions.east-half.hi    =  0.150   0.750   0.015

regions.middle.lo       =  0.000   0.100   0.000
regions.middle.hi       =  0.150   0.200   0.015

:bubbles: Specify Solids Region Settings

Here, we save:

  • Only solid0 in the west half
  • Only solid1 in the east half
  • Both solid0 and solid1 in the middle
mfix.solids.regions = west-half  east-half  middle

mfix.solids.west-half = solid0
mfix.solids.west-half.plot_per_approx = 0.04
mfix.solids.west-half.plt_vel_p   = 1

mfix.solids.east-half = solid1
mfix.solids.east-half.plot_per_approx = 0.04
mfix.solids.east-half.plt_vel_p  = 1

mfix.solids.middle = solid0 solid1
mfix.solids.middle.plot_per_approx = 0.04
mfix.solids.middle.plt_vel_p      = 1
mfix.solids.middle.plt_phase      = 1

:framed_picture: Visualization

The animation below shows the three defined regions visualized in ParaView:

  • Left: 1.245 mm particles (solid0) captured from the west half of the domain
  • Center: 0.76 mm particles (solid1) captured from the east half
  • Right: Both solid0 and solid1 captured from the middle section of the bed

:books: References

  1. Fullmer, W.D. (2025). Small-scale validation tests for MFIX-Exa CFD-DEM (DOE/NETL-2025/4951). NETL Technical Report Series. U.S. Department of Energy, National Energy Technology Laboratory, Morgantown, WV.

  2. Goldschmidt, M.J.V., Link, J.M., Mellema, S., & Kuipers, J.A.M. (2003). Digital image analysis measurements of bed expansion and segregation dynamics in dense gas-fluidised beds. Powder Technology, 138(2–3), 135–159.