LIGGGHTS® - User Forum

Hi,

I want to build particles of complex shapes through using the multisphere approach with LIGGGHTS. I use:

atom_style hybrid granular molecular
(...)
neigh_modify delay 0 exclude molecule all
(...)
fix freezing all rigid molecule.

So far I did simulations where the beads composing a particle of complex shape have the same size. Everything works nice! Now the beads composing the complex particle can have different sizes and here I face a problem.

I want to dump a velocity profile, averaged over pre-defined layers. To my surprise, there's a LIGGGHTS fix that does exactly this (ave/spatial).

I'm a little confused regarding the options: Nevery, Nrepeat & Nfreq. I've been experimenting with it but I'm still not 100% confident of what I'm doing.

What I think each option does:

Nevery: fetches new values every N steps
Nrepeat: not really sure.
Nfreq: compute average every N steps.

Hi,
I install colloid package by typing
make yes-colloid
make fedora_fpic

and I get no errors, ending with :

text data bss dec hex filename
2472063 93744 24 2565831 2726c7 ../lmp_fedora_fpic
make[1]: Leaving directory `/home/vajiheh/LIGGGHTS/liggghts_GIT/src/Obj_fedora_fpic'
vajiheh@vajiheh-desktop:~/LIGGGHTS/liggghts_GIT/src$

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