LIGGGHTS® - User Forum

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.

Noob question.
I would like to simulate particles falling down in a container filled with water. For now I do not need to couple with CFD, but I would like to able to tell the simulation that once the particles reach a given region, they are subject to an Archimedean lift.
But I am not sure how I can do it? Any simple example that I may have missed?
Thanks!

Hi guys,

I am trying to simulate a Direct Shear Box Test for soil.

I want to create two containers (two granular boxes, upper & lower) to contain the soil assemble and do the shearing.

To create the containers, I am thinking of wall/gran, however, I don't know how to group this walls together so that they become a container and move together, be able to read the force on it.

Please help me out if you have any thoughts or did something similar.