LIGGGHTS® - User Forum

Hi,
Is it possible in LIGGGHTS to do simulation with 2D granular packing with CAD imported in?
Thanks,
Ram

Hi everyone,

I'm now currently doing some force controlled test by LIGGGHTS via the if then else, next and jump commands. I can control the force of a wall by the displacement of the wall in some loops. But how can know the exact displacement from its initial defined position? It is difficult to track the loops to know the displacement by calculating the time step and its velocity because in my script the wall may move up and down by conditions. Are there any commands available to output a position of a wall after the condition reached in a loop?

Thank you.

Best

Hi everybody,

I found the following error message in liggghts version 1.4.5 as well in 1.4.4. I run a case with 209301 particles and 3 particle types on 8 cores (error message doesnt seem to depend on the number of cores). As pair style I use gran/hooke/history/stiffness 0 0. After setting up the case I get the following error:

IGGGHTS 1.4.5 based on lammps-10Mar10
Reading data file ...
orthogonal box = (-0.111 -0.111 0) to (0.111 0.111 0.039)
2 by 4 by 1 processor grid
209301 atoms
18118 atoms in group boundary
179086 atoms in group particle
Setting up run ...

Hi all,

I just wanted to check the meaning of the message:

"Temperature defined in fix wall/gran command is overruled by specifications in fix mesh/gran command"

Hello all,

what is the best way of incorporating walls into SPH simulations? I have tried three options (see attachment to this post):

1. hybrid pair style. somehow pair_hybrid seems to be incompatible with sph... probably because of the way how pair_hybrid determines the number of sub styles.
2. union of primitives. A particle penetrated into the wall. Lowering the time step by an order of magnitude did not help
3. mesh/tet and wall/region/sph. Apparently there are some implementations missing: ERROR: RegTetMesh::surface_interior()This feature is not available for tet mesh regions

Hi everybody,
I am interested in studying the behaviour at the contacts.

Is it possible to get the contact data from dump command in liggghts.

Could you please tell me how to dump the contact position and stress at the contact points.

regards,
Samantaray

I have been looking at the pair_gran_hooke_history.cpp file used by compute pair/gran/local command and noticed that in part unset non-touching neighbors, all the grains which are in a distance less than the sum of their radii are considered for the calculation, if I want to consider the touching grains not the overlapping ones too, can I simply remove the "=" sign in if (rsq >= radsum*radsum) and compile liggghts again?
further more if I want only normal forces can I put "fs1 & fs2 & fs3" in fs1 = - (kt*shear[0]);
fs2 = - (kt*shear[1]);
fs3 = - (kt*shear[2]);

Hi,
i have roller(stl import) and 1 granular atom inside. I use "moveStl all move/mesh/gran rotate" in it's axis.
It's all OK.

Then i need uneven atom so i make one rigid body from 102 atoms. And now rigid body go throughout the roller.. Why? What i make wrong?

atoms for rigid body are read with read_data. My data for read are someting like this:

data.rigid

102 atoms
1 atom types
-3 4 xlo xhi
-3 4 ylo yhi
-3 4 zlo zhi
Atoms
1 1 1.9 3620 -0.404 0.188 0.895
2 1 1.9 3620 -0.95 -0.309 -0.04

Hi,
I am simulating the pouring of particles in a container, but I got the error message
ERROR: Atom types must start from 1 for granular simulations
I used only one atom type but still getting this error. Can anyone tell why I am getting this error. Please find the input file below for reference

units lj
atom_style granular
atom_modify map array

boundary m m m
newton off
echo both
communicate single vel yes

region cyl1 cylinder z 0 0 5 0 10 side in units box
region con cone z 0 0 2 5 -5 0 side in units box
region cyl2 cylinder z 0 0 2 -10 -5 side in units box

Hi everyone,

As we know the command fix mesh/gran/stressanalysis command can analysis the stress on a wall. My question is how to use the pressure analysed by this command to control a loop in a script file. If I output the pressure on the wall first to a dump file, can I use any command to read the pressure in the dump file and then use it in the loop? Anybody can help me?

Many thanks.

J. Wang