CFDEM®coupling - User Forum

Dear CFDEM users,

I have been running some IB-solver cases with a high demand on computational power. For that reason I had to start sometimes with a relatively small timestep before increasing the timestep of the simulation after some time.

To reload the DEM particles in my restarted simulation I use the read_dump command. Now, however, when implementing more than 10 particles with the read_dump command I obtain the following error within my LOG-file :

Dear all,

I have a question that, as we know for the unresolved model, the particle size should smaller than the CFD cell size, and the value of Vcfd/Vdem = [3,10], for big particles, as Vdem/Vcfd >10, maybe we can consider to use the Resolved model. But in this between, how to deal with the case with Vdem/Vcfd in the range of [1,2]. Is there any volume fraction model can deal with this? Whether the tri-linear volume fraction model can deal with this? If could, is the tri-linear volume fraction can only be used for cubic cell (cell_x = cell_y = cell_z)?

Thank you!

Hello. Could someone help me compile CFDEM. Follow all the steps of tutorial. and continues to appear ERROR 1. When I type cfdemSysTest appears:

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Hi, All:

I have a large simulation and I want to suppress the screen output for the CFDEM coupling to increase the performance, I have disabled OpenFOAM debug info by setting debug swithes:

DebugSwitches
{
SolverPerformance 2;
}

However it seems I am still getting the debug information from the LIGGGHTS/CFDEM side (see below), is there anyway that I can disable those output?

Can anyone comment the right syntax for particle growth and shrinkage problem. I need to increase the radius of 200000 particles from 100 micron 125 micron.

Thank you

Hi~ i have a question for drag force.

nowdays, i study a simulation flow about liggghts, especially, coupling with openfoam.

i want to find how to affect flow( liquid or gas) to particle. so, i look at files for coupling(fix_cfd_coupling.cpp, fix_cfd_coupling_force.cpp and so on)

I found a drag force add to orient force(f[]) in function post_force(int).

but i could not find how to calculate dragforce( fix_dragforce_->array_atom).

Where is this force calculated?

thx for read my question, with my odd(?) english.

I want to restart an integration in a cfdem calculation after performing a group update at every coupling step. I tried to use the execute option of the liggghtsCommandModel. However, when doing so I get an error connected to the restart of the integration in the fourth execute command. The other execution commands seem to work fine. Is it possible to start an integration form liggghtsCommand?

liggghtsCommands looks the following

Hi Everyone,

Quite recently this article by (amongst others) Bruno Blais was publised.

http://www.sciencedirect.com.tudelft.idm.oclc.org/science/article/pii/S0...

It mentoins that due to the low minimum fluidization velocity and particle relaxation times the implicit momentum coupling can be problematic due to pressure oscillations.

I have a stream of particles in a fluid flow and want to write the data of paticles entering a certain region to a file. To do this I need to dynamically update the group assignments of my particles.
In Liggghts the following works fine:
run 1e5 upto every 100 &
"undump dmp2" &
"group nve_groupOut delete" &
"group nve_groupOut region regOut" &
"dump dmp2 nve_groupOut custom ${outInt} ${path}/DEM/post/dump*.out id type type x y z ix iy iz vx vy vz fx fy fz omegax omegay omegaz radius"

Hello all,

I want to validate the drag acting on a particle with a CFD-DEM terminal velocity test. I have created a small domain which is periodic in height direction with particle at the center.

I don't want fluid to feel the movement of particle, else the particle enters the domain already accelerated by the fluid.

Is it possible to get this done on the fly without playing with Ksl in cfdemSolverPiso.C?

thanks!

Kind regards,
Vinay