LIGGGHTS® - User Forum

I'm using LIGGGHTS 2.0.3, and in my input script this line is giving me trouble:

fix xwall active wall/gran/hertz/history primitive type 2 xplane ${wall_xlo} ${wall_xhi}

where the wall_xlo and wall_xhi variables are defined earlier. This gives the error:

ERROR: Fix wall/gran/hertz/history (id xwall): invalid keyword or keyword(s) in wrong order (fix_wall_gran.cpp:224)

According to the documentation, this syntax should be correct.
A little bit of debugging brought me to this section of code beginning at line 56 of primitive_wall_definitions.h:

Dear friends,

I have installed "LIGGGHTS-PUBLIC" on my desktop computer and then run my code in the LIGGGHTS without any error with this command: liggghts < in.liggghts_1

But when I tried to run it in the parallel processing mode ( mpirun -np 4 liggghts < in.liggghts_1), it was not possiable.

I received the following message:

mpirun was unable to launch the specified application as it could not find an executable:
Executable: liggghts
Node: ubuntu
while attempting to start process rank 0.
--------------------------------------------------------------------------

Hi,
I have a problem one moth ago, and I tried to fix the problem, but is very difficult to understand.

I am trying to simulate the transport of grains in a single screw extrusion, for that i build two wall in STL format. One wall is rotating and another one does not move. I am using gran/herzt/history interaction and wall/gran/hertz/history for the wall and particles.

Firstly, I use particles of d=3mm, normally the message "WARNING: Dangerous build in triangle neighbor list." appears but the run does not stop, and the post-processing corresponds very well to the results expected.

Hi there,

I need to add a new force model to account for DLVO interactions between particles, with eachother and the walls. I need that to work with coupling of CFDEM as well. can you please help me how to start and where should I look for some hints?
thanks alot,

Dear developers and users of LIGGGHTS,

I can't set z-plane walls to wiggle in LIGGGHTS using fix/wall/gran.
When I use walls from a CAD file (mesh/gran) then wiggle works fine.

Hi,
I need to calculate coulombic interactions (coul/debye or coul/long) between my particles with eachother and walls of domain, however, Colloidal package for LAMMPS is not installed on CFDEM. I appreciate if you let me know how to add it. besides, I need to define colloidal walls for some of the walls, but I do not have a simple rectangle, and fix wall/colloid cuts in my domain. I appreciate if you help me how to define colloidal walls for my imported mesh from cad.

thanks,

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