LIGGGHTS® - User Forum

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

hi all, i have jst installed liggghts and i dont knw how to start it using terminal. is there any user guide or documentation of liggghts so that i may learn this?

hallo ,
can anyone help me with good way for creating 3d box Obstacle in 3d flow using LAMMPS

?!
since fix indent supports just plane cylinder and spheres !!?

Hi my friends,

Are there anybody can explain a very basic question for me? In the document about the fix pour/dev/packing commad, it says:

vol values = fraction Nattempt
fraction = desired volume fraction for filling insertion volume
Nattempt = max # of insertion attempts per atom

What's the meaning of max # of insertion attempts per atom? Is it the maximum number of particles inserted in the box? What will happen if the maximum number of atoms have been reached but the desired solid fraction has not got yet?

Thanks.

Wang

Hi!
Is there some upper limit from the LIGGGHTS to the one and page values? If I increase the page value too much, I get memory error, when run is executed. If this is not an LIGGGHTS related, do you know is this Linux or hardware related issue? I'm using 64-bit Linux on distributed memory cluster with 8GB RAM on each node, and the LIGGGHTS is executed parallel in a distributed way.