How to track different solid phases in DEM

MFiX How to
#1

Hi all,
I am trying to track different solid phases in DEM simulations. If I create two different kind of solids but of same properties, it is impossible to me how to distinguish them. Enabling “vtk_part_phase” does not create a useful output. I tried also Paraview and Tecplot output formats and none of them make a distinction between the solid phases.
Thanks

1 Like
#2

You can define e.g. 2 DEM phases like:
MMAX = 2
SOLIDS_MODEL(1) = ‘DEM’
RO_s0(1) = 1000
D_p0(1) = 0.04

SOLIDS_MODEL(2) = ‘DEM’
RO_s0(2) = 2000
D_p0(2) = 0.02

For the vtk part, something like:
vtk_dt(1) = 0.2
vtk_data(1) = ‘P’
vtk_x_w(1) = 0.0
vtk_y_s(1) = 0.0
vtk_z_b(1) = 0.0
vtk_x_e(1) = 0.6
vtk_y_n(1) = 0.6
vtk_z_t(1) = 0.6
vtk_filebase(1) = ‘particles’
vtk_part_density(1) = .True.
vtk_part_diameter(1) = .True.
vtk_part_vel(1) = .True.
vtk_part_id(1) = .true.
VTK_PART_PHASE(1,1:2) = 2*.TRUE.

1 Like
#3

If you want to distinguish the 2 phases, you can either:

  1. set vtk_part_phase_id(1) = .True. : Each particle can be colored by its phase ID
  2. Create 2 vtk regions: In region 1, set VTK_PART_PHASE(1,1) = .TRUE. and VTK_PART_PHASE(1,1) = .FALSE. . In region 2, set VTK_PART_PHASE(1,1) = .FALSE. and VTK_PART_PHASE(2,1) = .TRUE. . This will write Phase 1 particles in the first vtp files and phase 2 particles in the second vtp. Open both vtp files in Paraview and toggle the visibility of the vtp files to isolate a given phase.
3 Likes
#4

Thanks Yupeng and Jeff for the answers,
I solved the issue. The problem is that both solids where identical and the parti_phase output I get was 1 for all the particles, changing any property of any of them make it work properly.
Now my question is if two identical solids cannot be tracked separately?
Regards

#5

Yes they can as long as they are different phases, As Jeff and Yupeng have described…

#6

Hi Justin,
I tried both (indeed what Yupeng suggested is actually what I was doing) and both produce an output of 1 for the particle phase.
I attached the mfx file with the last modification proposed by Jeff which only exports one of the two vtk regions.
dem2solids.mfx (11.2 KB)