LIGGGHTS® - User Forum

Hi there,

I'm trying to determine all the top particles of my pebble bed (so basically the top layer) in order to figure out the average z-coordinate of these particles (the z-coordinate of the top layer particles slightly vary, obviously.)

Is there a clever way to do so?

My idea was to pick my top particle with bound(all,z_max) and then put all atoms which are in the range of (z_max - particlediameter) in one group. But then again, how do i get the average z-coordinate of this group of particles out of it?

Hopefully someone can help me here.

Hello Everyone
I am trying to simulate grain flow in a desilting chamber. Somehow i managed to create an input file and have rectified most of the errors but i am not able to understand this ("ERROR on proc 0: Too many atom sorting bins") error. Could someone please help me with that. The input file is attached.Thanks in advance.

regards
vipul

Hi everybody,

I'm looking for an effetive way of wiggling a pebble bed in order to reach a high packing factor.

When using the "fix_move wiggle" command I need to set the amplitude vector and the period of oscillation.
I'm not sure which values are best for effective wiggling? Right now I'm using an amplitude of about 1/10 particle diameter and an oscillation time of 0.0005, but my results are quite unsatisfying.

Hoping someone can help because this is driving me nuts! [Maybe solved, see bottom of post]

Sometimes the indenter interacts with the particles as expected, and other times the indenter seems to pass through the particles with no effect. I've been having this problem for some time so I tried to narrow down the cause. I use a workstation running Ubuntu, and a large HPC cluster, and both run the executable compiled with 'make fedora'

I've attached two input scripts (plus associated stl file) in which I'm trying to move an indenter into a box of particles.

Can someone assist with the procedure/steps for importing CAD geometries into LIGGGHTS?

Hi!

Could you tell me a way to dump the overlap statistics for each timestep?

Regards and thanks in advance,

TM

Can anyone help me understand the rotation of shear displacement in LIGGGHTS? The update of shear[0] += vtr1*dt is fine, but I am bit confused with shear[0] -= rsht*deltx. Why has it to rotate and why it is a minus?
Many thanks.

(Problem solved)

Hi All,

I am not sure why, but when I compile the LIGGGHTS 2.0 RC code I have had the fix_wall_gran file replaced with an older version that does not include "unregister_compute_wall_local". Perhaps someone has an idea why this happens. I have posted the error I receive when compiling.

compute_pair_gran_local.cpp: In destructor ‘virtual LAMMPS_NS::ComputePairGranLocal::~ComputePairGranLocal()’:
compute_pair_gran_local.cpp:102:17: error: ‘class LAMMPS_NS::FixWallGran’ has no member named ‘unregister_compute_wall_local’

Hi I've created a simulation where a small fraction of the overall number of particle in the simulation experience a large force relative to the other particle in the simulation. Does anyone know if it is possible to get LIGGGHTS to count the number of particles experiencing a force greater than say fior example 10N? I guess this could be done using a logic statment but i'm not sure how to go about it.

Hello all,

I am generating a txt file for the read_data command and I am getting an error that I just cannot figure out! If someone could be so kind as to take a look at this for me, it would be very much appreciated.

My input file is the following:
##
units si
atom_style hybrid granular molecular
boundary f f f
newton off
communicate single vel yes
read_data read_data.txt
mass * 1.0

###################################
# no boundaries for now...
fix 1 all gravity 9.81 vector 0.0 0.0 -1.0
fix 2 all rigid molecule
neigh_modify exclude molecule all