LIGGGHTS® - User Forum

Hello,

I'm trying to fill a cylinder with cohesive particles, using Hertz and a certain particle size distribution. However, the particles bounce around and/or then just seem to dissapear. I'm not sure whether they go through the wall or if they bounce out of the domain. Initially, I had no problems, but now I do. Changes I've made include switching from Hooke to Hertz, switching from legacy/pour to insert/stream (to allow a PSD), and adding cohesion, but I'm not sure what causes the problem.

Any help would be appreciated. I've added my code below.

hi all,

dt_h = 2.87*(m_eff^2/(r_eff*Y_eff^2*v_max))^0.2

I understand the concept/calculation of effective mass,radius and young modulus for particle-particle.
Eg: 1/m_eff = 1/m1+1/m2; (m1, m2 are masses of two particles).

How is liggghts code calculating for particle-wall? What can the mass of wall be? Is it going to be infinity?

Please help.
Thank you.

Hello,
I'm simulating an continuous mixer, which mixes molecules and spheric particles.
The molecules are created continuously and inserted in to the mixer. The molecules are stored in group grpm.
The granular particle are generated classically with the fix insert.... command.

Hi

Does anyone have any experience with the "lubrication force" between particles? Is the "lubricate" pair_style in LAMMPS/LIGGGHTS the same as what many papers use as the lubrication force? It looks like a totally different formula in the code.

e.g.: Zhang, W., Noda, R., and Horio, M. “Evaluation of Lubrication force on colliding particles for DEM simulation of fluidised beds”. Powder Technology, 158, pp 92-101, 2005.

Thanks
Evan

There was a previous post where I discussed a method of making fairly dense random packings of rigid molecules. Here is the python script I wrote. It is fairly well commented for the procedure.

I have not tested it on LIGGGHTS 3.10 yet, but the output file would work as a restart file for LIGGGHTS 2.3.8.

Hi,

I try to dump out the particles information with

dump id all custom 2000 post/dump.fill id type x y z ....

but it stops writing out dump files over 2.1 GB. The dump files of the meshes are still created but not the particle ones.
what could be the problem?

thanks in advance
Joshua

Hello all,

I'm simulating a particle system with multiple particle sizes (D [mm]: 0.5, 1.0, 2.0, 3.0, 4.0, 5.0). I'm wondering what kind of settings can reduce computational time? Has anyone done some research on this?

Hi all,
I looked in manual and found "partition" command for dividing the total area into multiple partitions, each partition is assigned a different number processors. But I could not exactly understand how? If anyone knows, please tell me how!

Regards
Elham

I have to write a script that generates a cylindrical container (radius 12.5 mm and height 150 mm) filled with a random packing of 500 glass spheres having the same radius (for example 1 mm).
I am interested only in obtaining the spatial coordinates (x,y,z) of the spheres after running the simulation.
How could I write this script?

Hi, All

I am trying to use the servo controlled wall (shear cell example in http://www.cfdem.com/forums/liggghts-tutorial) in LIGGGHTS 3.2.0 (the latest), there is always an error for the below lines (line 66-69), the file is attached:

fix cad3 all mesh/surface/stress/servo file top_plate.stl type 1 scale 0.001 &
stress on com 0 0 0.06 dim z ctrlPV force target_val -10.0 vel_max 1.0
fix geometry2 all wall/gran model hertz tangential history mesh n_meshes 1 meshes cad3