LIGGGHTS® - User Forum

I'm trying to simulate a 2D box with a fixed number of particles (spheres). Once the particles are inserted, one of the walls moves to pack the configuration, while the opposite wall rolls using the conveyor option. I got this part working. My problem is the following: I read in these forums that it's advised to use a thin simulation box instead of the 2D-related commands. I managed to get the thin box with the following lines:


region reg block 0 0.85*${sigma} 0 $l 0 $l units box
variable tmp equal $l-${sigma}
region insreg block 0 0.85*${sigma} 0 $l 0 ${tmp} units box

Hi everyone,

I am using LIGGHTS 2.0.1. and I am having a problem with "unfix". I'm trying to move walls using "fix", run for 40 steps, stop wall movement using "unfix" and run for another 160 steps, as shown below. It keeps saying this:

"ERROR: Illegal deletion of a fix move/mesh. There is another fix move/mesh command active on the same mesh. Superposed fix move/mesh commands must be unfixed in reverse order of creation"

I've tried all possible combinations of the unfix command, but the same problem persists. Any ideas on what's going on?

Hello, Christoph, right now I am testing the latest version 2.0.1 of LIGGGHTS. I got very strange error message about "pari_style". I used "pair_style gran/hertz/history", however I got the following error message " ERROR: Illegal pair_style gran command, illegal keyword (pair_gran_hooke_history.cpp:459) " .

Hi, is there a way to impose limits on particle velocities? although my time steps are well in the range on 0.1 rayleigh number (using fix check/timestep gives no warnings), I still get overlap of two particles and as a results elimination of one particle in contact with the other. it is the same with the walls. I was wondering to impose a limit to particle velocities? can you please help me how to do so?
(particles have radius of 3e-3, density of 1.8, and young modulus of 1e6, cells are 0.015 cm, time step is 1e-8 s, all in cgs system)
Thanks,
Vajiheh

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