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MFiX 20.4 Release Announcement

We are pleased to announce the MFiX 20.4 release. Please visit the download page to download the latest version. See the release note below that highlights the changes from the previous version.

Please visit the MFS forum for any software related questions, or send administrative questions to


The MFiX Development Team

New features:

  • Coarse Grain DEM [1]: Eulerian/Lagrangian model similar to DEM, where particles are grouped into larger coarse-grained particles (CGP). It is more affordable than DEM since fewer CGPs need to be tracked. The collisions between CGPs are resolved the same way as in DEM. This modeling approach falls between DEM and PIC in terms of computational resources.
  • PIC collision damping: An empirical collision damping feature has been added to the MFIX-PIC model. The feature includes a calculation for collision frequency based on statistical likelihood. From this frequency, a small change in velocity is calculated and applied to parcels locally. The effect is an overall damping of solids velocity, particularly in areas where dense particle flow is apparent.
  • New particle_output.dat file: A new particle_output.dat file can be saved at the end of a DEM or CGP simulation. This is an ASCII file that has the same format as the particle_input.dat file. The expected use of this file is to save the particle configuration (say after settling a bed of particles) and use it as initial condition for another simulation (the file must be renamed particle_input.dat).
  • Option to visualize the [RUN_NAME]_MESH.vtu file in the model view.


  • The background color of the VTK window can be customized. Users can select two colors to create a vertical gradient.
  • Option to save images with transparent background.
  • Three tolerances are now keywords. Although it is not recommended to change their default values, DIL_EP_S, ZERO_EP_s, ZERO_X_gs are now keywords (Numerics > Advanced pane) and can be changed without needing to edit the source code and building the solver.
  • New project filtering of list of templates is more user-friendly.

Notable bug fixes:

  • Fixed bug that was unsetting vtk_part_x_s when opening a .mfx file.


[1] Lu, L., Gao, X., Shahnam, M. and Rogers, W.A., 2020. Bridging particle and reactor scales in the simulation of biomass fast pyrolysis by coupling particle resolved simulation and coarse grained CFD-DEM. Chemical Engineering Science, 216, p.115471.

Changes from 20.4.0 to 20.4.1

bug fixes

  • Fixed particle phase ID not being properly set for Coarse Grain DEM simulations
  • Fixed failure to read the mesh file when using Dynamic Load Balance
  • Fixed occasional failure to write the particle_output.dat file when running a simulation in parallel (DMP)
Changes from 20.4.1 to 20.4.2

Bug fixes

  • Fixed keyword argument error when saving a project with chemistry from GUI
  • Write physical diameter instead of physical radius in vtp file (Coarse Grain DEM simulations)
  • Avoid division by zero in comp_mean_field0
  • Fixed data check error with usage of bc_po_apply_to_des keyword
  • Fixed wrong particle sized being assigned when reading particle_input.dat file (Coarse Grain DEM simulations)
Changes from 20.4.2 to 20.4.3
  • Fixed bug that affected the parsing of heats of reactions on some gfortran compilers with optimization flags