LIGGGHTS® - User Forum

Hi

Im able to run the simulation and in paraview observe the mesh created through stl file.
Also I changed the scalefactor from 1 and 0.1 and was able to appreciate the difference in size of the mesh.

My problem is the offset. I tried to move the mesh by changing the xoff, yoff and zoff, but nothing happens. The mesh always stays in the same place.

Have someone had the same kind of problem?

Hi everybody,

I'm looking for an effective way to generate a dense bed of spherical particles in a 2d simulation.
I hoped that fix_pour_dev_packing could be used for that - also the doc says that - but since one has to use fix_particledistribution_discrete together with fix_particletemplate_sphere which cannot be used in 2d simulation it seems to be not possible.

Is there any other way to generate dense packing in 2d simulations effectively instead of simulating all the pouring process?

Thanks for the help,
kind regards,

Sebastian

Hi guys,

I am doing the simulation of shear box test, I split the simulation into packing (based on the packing example)and shearing.

As a trial run, about 200 particles are inserted and it works just fine for the packing part. But in the shearing part,
I used the:
1. fix rigid command to create a rigid body to push the particles contained in the "upperbox and lowerbox"
2. fix move/mesh/gran to move the lower box to do the shearing.
However, just when I added force on the rigid body to push the particles, system stopped and printed:

Dear community,

weeks ago I posted some questions regarding a set-up of a mill simulation.

Now, after much help from richti83, the ball mill simulation progressed.

But one problem still remains: the balls are "glued" to the lower(!) part of the lifting bar (see attachment).

I couldn't fix this problem. I tried to mesh it via GMSH, I drew it with ProE with zero wall thickness (bars had still thickness) then exported it to STEP and finally to STL, I tried to increase the wall thickness but it did not help either - the balls are still under the lifting bar when rotating (nonsense).

I am a beginner of liggghts and need to make a simulation of oedometer test which is a one-dimensional test and the clay sample is immersed in water, the top wall and bottom wall allow the passage of water during consolidation. The followings are my questions :

1. Should there be two types of particles , one is the clay particle and the other one is water particle?
2. How can I create the wall which allow the passage of water particles but not for clay particles?
3. Could anyone send me example of the script of simulation of oedometer test?

Hi guys,

I am now still testing the packing of particles and I used the packing example.
Differently, I used the pair_style of gran/hooke/history/stiffness 1 0 and tried to used slightly smaller particle size (I tried 3mm but failed), I also import mesh from stl files generated by Gmsh.
My problem is:

1. the Pour/dev function actually insert much less particles into the region, (less than 100), but the region is big enough to contain a lot more particles.

Hello all,

Hi guys,

I need to create walls using mesh/gran command and wonder how to create these walls through stl from CAD?

Many thanks

Hi guys,

Base on the example of in.packing, I am trying to do a packing similarly.
Different from the example, I use pair style of gran/hooke/history/stiffness instead. I don't think it would be problematic but the system crash down when it came to the nve integration,
Here is the output of the screen:

LIGGGHTS 1.4.4 based on lammps-10Mar10
Created orthogonal box = (-1 -1 -1) to (2 2 2)
1 by 1 by 1 processor grid
0 atoms in group upper
0 atoms in group lower
0 atoms in group total

I created ideal walls and want to use the fix wall/gran/hertz/history/stiffness command and the syntax of this command is:

fix ID group-ID wall/gran/(*) friction_damp_flag cohesionflag wallstyle args keyword values ...

I don't really understand the group-ID here, does it mean the ID of the group that I want to create walls to bound? or the ID for the group of the walls themselves? How to "group" these walls? they don't consist of particles.