LIGGGHTS® - User Forum

Although liggghts runs perfectly well, just need some advice on how to optimise runs for speed (particularly for granular flows with many particles).
Best regs,
BrianW

Big fat disclaimer:
I come from a Slackware background, but since I expect most LIGGGHTS users out there to be running RHEL/Scientific Linux/CentOS/Fedora, I have made two assumptions regarding the build variable used by automake/autoconf in OpenMPI and FFTW. Replacing "--build=x86_64-redhat-linux" with something suited to your distro should be trivial. (To find out what build variable you should use for your distro, execute the command "gcc -v" and look in the output for "--build=".)

Assumptions

Hi all!
i created a box and divided it into two parts(regions).The particles are poured in one region and are made to move into the other region and the particles can be seen moving in paraview.But when i see the dump file(region), all the particles are shown in the same region and they do not change their region with the passage of time.As the region is a static command, Is there any solution of this ? Actually i want to know the number of particles in each region after some specific time intervals.
If anybody knows please help.Thanks
sajjad

Hi all
i want to know that is it possible to wiggle an imported mesh wall by using the " wiggle " command.
if any body help, i will be thankful.
sajjad

hi all ! i am new comer in liggghts. i made a box and then divided it into two parts by importing an mesh wall(STl file).
I poured the particles on one side of the box. When i applied wiggle command the particles penetrate into the imported wall and cross it. i want the partcles should not cross the wall. there is my input file. If anybody help me i will be thankful.
sajjad

# Wall import from CAD

atom_style granular
boundary f f f
newton off
atom_modify sort 0 0

communicate single vel yes
units si

region reg block -0.01 0.51 -0.01 0.25 -0.01 1.31 units box

I use a geometry defined by an STL file and I move downwards another rectangular plane in order to wipe out some volume from atoms. In this empty volume I create some new atoms and I want to remove the former plane that separates the new atoms from the others.

When I unfix this rectanglular plane I receive a segmentaition fault (see below).

What I'm doing wrong? Is it possible to unfix wall/gran/hooke/history?
Or is there a better strategy to:
1.) pour a certain no. of particles in a STL defined geometry
2.) create an empty region keeping the no. of particles const.

Hi LIGGGHTS users,
I have one simulation box and it is divided by mesh wall into two boxes. One box is filled with two types of particles and when I wiggle it using wiggle command the particles cross the mesh wall and come into the other box.
Please anybody can troubleshoot the error? Thanks in advance.
Best,
Ram

Hi Christoph,
Could you please let me know, if LIGGGHTS can help me to run a triaxial compression test on a cylindrical shaped assembly of particles. Lateral wall under constant pressure, fixed bottom, and strain(velocity) controlled loading at the top. Any response from you will help. Thank you in advance.
Regards,
Carlos

Hi Everyone

The "dump custom" has the option for writing "fx fy fz". I assume these are the resultant total unbalanced force per sphere.

Is it possible to dump the contact forces (between spheres) and the contacts' positions?

Thank you

Alexander

Hi Christoph,

Concerning the stress computed with the command: mesh/gran/stressanalysis

In my simple compression test, I have these lines:

fix topwall all mesh/gran/stressanalysis topwall.stl 1 1. 0. 0. 0. 0. 0. 0. # Insert top wall
fix bottomwall all mesh/gran/stressanalysis bottomwall.stl 1 1. 0. 0. 0. 0. 0. 0. # Insert bottom wall

fix wall all wall/gran/hertz/history 1 0 mesh/gran 2 topwall bottomwall #Contact properties

fix F_movetop all move/mesh/gran linear 0. 0. -0.0001 units box topwall 1 #Wall motion