CFDEM®coupling - User Forum

I have examined some of the original literature on the drag force models used. Am I correct in stating that when using the Koch Hill drag force model, the Archimedes buoyancy model should NOT be used as it is 'included' in the Koch Hill model by their definition of drag force? Or has the Koch Hill drag force model been modified by a factor of the fluid fraction to 'remove' the buoyancy term?

On the other hand, the Archimedes buoyancy force does need to used when using all the other drag force models, correct?

I have been examining the available drag models available and I have a number of questions. Your time in addressing these is most appreciated.

When examining the Schiller Naumann drag model implementation, the drag term is given by;
drag = 0.125*Cd*rho*M_PI*ds*ds*magUr*Ur
- why is the scalar term 0.125 and not 0.5?

When examining the Koch Hill drag model implementation, the Reynolds number term is given by;
Rep = ds/scale_*voidfraction*magUr/(nuf+SMALL)
- is scale_ = 2? or if not, what is this term?
- what is the SMALL term?

Hi All,

The attached file is the detailed steps for installation of OpenFOAM-2.2.x, LIGGGHTS, and CFDEMcoupling. Hopefully, it does help for the new users.

But, after coupling, it shows
%Note: the list of utilities compiled might be incomplete.
please check /home/cee-student/CFDEM/CFDEMcoupling-PUBLIC-2.2.x/applications/utilities for more utilities available

For the Test case and cfdemSolverIB, it has no problem.

In the DEM inpustscript file, I use the comand:
compute dragtotal all reduce sum f_dragforce[1] f_dragforce[2] f_dragforce[3]
#screen output
compute 1 all erotate/sphere
thermo_style custom step atoms ke c_1 vol c_centerOfMass[3] c_dragtotal[1] c_dragtotal[2] c_dragtotal[3]
thermo 10
thermo_modify lost ignore norm no
compute_modify thermo_temp dynamic yes
#insert the first particles so that dump is not empty
dump myDump all stl 1 ../DEM/post/dump_*.stl
#run 1

In the couplingProperties file, I did not choose any drag force models, but when I run the simulation and use the LIGGGHTS
input script to dump the drag force, found the drag force is not equal 0.

Hi everyone,

Hi All,

Does anyone please let me know how to update the version of LIGGGHTS? The current version for me is LIGGGHTS 1.5.3 based on lammps-10Mar10, which is installed last year. And I have not been used it for a long time. Recently, I need to pick them up again, and the newest version is LIGGGHTS 2.3. And I tried to use "git pull" command under the directory of "LIGGGHTS-PUBLIC" to update it, but it shows "Already up-to-date".

One problem for the old version of liggghts is running the test examples of CFDEM. In the terminal, it shows

Hi everyone,
I try to coupling results from the restart file, however, it shows an error as "WARNING: Restart file used different # of processors (read_restart.cpp:517)
WARNING: Restart file used different boundary settings, using restart file values (read_restart.cpp:588)
orthogonal box = (-0.5 -0.5 0) to (0.5 0.5 0.5)
1 by 2 by 1 MPI processor grid
ERROR: Invalid bond style (force.cpp:280)". Is it related to the coupling properties or the liggghtsCommand? Does anyone know how to modify it? Any help would be thankful.

Dear all,

first test with OF 2.2.x look promising (compilation and first test runs work fine).
I experienced that the probes utilities now write to Case/CFD/postProcessing/probes, which demands the paths in Case/CFD/octave/*.m to be adapted accordingly.

Please keep us posted if you experience problems with CFDEMcoupling 2.5.1 and OF2.2.x.

Kind Regards,
Chris

Hi everyone,

I am trying to see the velocity of one particle with coupling and I modified the liggghts input and the related changes of the tutorials of SettingtimeMPI. However, the results for the cupling are all zero. I attached my liggghts script and the results file. Does anyone know how to modified it? Is it related to coupling properties? Thank you.