LIGGGHTS® - User Forum

hello all,
I am new on liggghts as well as Cfdem. i have installed Openfoam, liggghts and cfdem on ubuntu-10.04 LTS as per guidance in the installation text file given on this website. to learn liggghts properly i chose 'packing' example given in LIGGGHTS and i entered following commands in terminal:

cd LIGGGHTS/liggghts_GIT/example/LIGGGHTS/packing
cp ../../src/lmp_fedora_fpic .
lmp_fedora_fpic

i have 3d cavity case , and i want to have a middle section on x direction
suppose the section is 2d plane
i need to have as out put :
lattice ID on Y || lattice ID on Z || averaging spatial velocity on X ||
how can i do this .. since fix/ave give layers averaging and not lattice by lattice !!!
thankx

Hi everyone,

I'm now trying to press a packing by a meshed wall to reach a specific force. But it's always error and I don't know why. May anyone have a check and give some hints for me? The commands I use is as below:

fix topwall all mesh/gran/stressanalysis topwall.stl 1 1. 0. 0. 0. 0. 0. 0.
fix F_movedowntop all move/mesh/gran linear 0. 0. -${vc} units box topwall 1
label movedown
run 100
variable F equal f_topwall[3]
if '$F>999.99' then "jump banlance"
variable F delete
jump movedown

hallo ,
i am running simulation of a cube ,,
so i want to devide it with special number of lattices ,, but since that number is not big ,, i get so less particles ,
which let particles in flow domain ,,get through the wall boundary !! which is catastrophic mater !!!!:(
i tried to define the boundayr as a waal with wall/reflect ,, it didnt work although i satisfied the condition ( not periodic boundayr condition )

Hy @ all,
today I tried out a new Ligghts-simulation. There were no problems at the beginning of the simulation, but suddenly the following error message occured and the simulation stopped:
---------------------------------------------------------------------------------------------------------------
23000 14880 2.2231925e-05 7.6922864e-06 0.09
24000 14880 2.7485182e-05 7.5921738e-06 0.09
25000 14880 3.1203901e-05 7.4077441e-06 0.09

Hi!

I have two issues,
1, my simulation is somehow crashing when I leave it overnight, so is there a way to output the real time after each calculation? I would prefer it to elapsed cpu time.
2. After restarting the simulations, the loop time shown is for the steps after restarting, is there a way to to get the total simulation time including that of previous restart?

Regards,

Hello.
Seems, if a mesh face size is < a particle diameter then interaction between them is wrong.
Is there a advisable ratio between them?

ps/
I attach my test case for this problem.
Here you can download my results for the case:
http://dl.dropbox.com/u/714488/liggghts_fine_stl_test.avi

Hi,
Is it possible in LIGGGHTS to do simulation with 2D granular packing with CAD imported in?
Thanks,
Ram

Hi everyone,

I'm now currently doing some force controlled test by LIGGGHTS via the if then else, next and jump commands. I can control the force of a wall by the displacement of the wall in some loops. But how can know the exact displacement from its initial defined position? It is difficult to track the loops to know the displacement by calculating the time step and its velocity because in my script the wall may move up and down by conditions. Are there any commands available to output a position of a wall after the condition reached in a loop?

Thank you.

Best

Hi everybody,

I found the following error message in liggghts version 1.4.5 as well in 1.4.4. I run a case with 209301 particles and 3 particle types on 8 cores (error message doesnt seem to depend on the number of cores). As pair style I use gran/hooke/history/stiffness 0 0. After setting up the case I get the following error:

IGGGHTS 1.4.5 based on lammps-10Mar10
Reading data file ...
orthogonal box = (-0.111 -0.111 0) to (0.111 0.111 0.039)
2 by 4 by 1 processor grid
209301 atoms
18118 atoms in group boundary
179086 atoms in group particle
Setting up run ...