LIGGGHTS® - User Forum

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

Hi everyone,

I try to make a simple compression test (see different attached files) from a cohesion sphere packing. Therefore, the top wall modeled by mesh is moved down.

But I have a strange simulation (you can run it from the attached file), there are not stresses computed (see ./post/Stress_file-*) on the top wall. Moreover the top wall only push some spheres.

I am a beginner, so it is possble that I done a mistake. if anyone can explain me it, I will be fine for me.

Thanks
Jf

Hi friends,
I found this error in new liggghts-1.1.2. The same file is working in old version without any error.

WARNING: STL face normals were not normalized, normalizing
Mesh calculations running. This may take a while...ERROR: STL import failed because triangles #0 (line 1) and #960 (line 6721) are duplicate
[ram@localhost rect]$

Please anybody there who can figure out the error...?!
Best,
Ram

I have downloaded the tar ball for version 1.1.1, I am struggling with the make fedora command in the /src directory

Operating system: Fedora 13 – 32 Bit

+ Install paraview by typing "sudo yum install paraview" in a console – only works if i run the command as root
+ Install Open MPI by typing "sudo yum install openmpi openmpi-devel" in a console – only works if i run the command as root

Updated the sudoers file to allow the my username...

I think paraview & Open MPI is installed correctly will it make a difference if i install as root?

Is it possible to use two different movements (e.g. wiggle and linear) on one mesh object?

I applied two different wiggle movements (0.0005 NULL 0.0003 and NULL 0.0007 NULL) with different periods on the object and is works. In addition I wanted to move the object linear while still "wiggling" but the wiggle stopped. Any suggestions?

Regards, Christian

Hi evereyone,

I have a naive question. I try to generate a random cubical sphere packing by iterative growing from a cloud of spheres.
But I have two problems :

1) I don't know, How can I indicate the growing increment at each step for the spheres.
2) I don't know, if it is possible to put this increment equal to zero when the solid fraction or the compacity reaches a fixed value.

if you have few indications to give me, please don't hesitate.

Thanks

Regards
Jf

Christoph,

What do I do wrong using the "fix/rigid" in a LIGGGHTS simulation? I tried to produce the same input for LAMMPS and LIGGGHTS but I get an error with LIGGGHTS: (Line numbers are on) This input is for LAMMPS; for LIGGGHTS line 9 is commented out and line 10 and 15-19 are uncommented.

Thanks,
Christian

==========
1 # Simple rigid body system
2
3 atom_style granular
4 newton off
5 communicate single vel yes
6 units si
7 neighbor 0.002 bin
8

Hi Everyone

I am running a model of a drum with spheres in it. The drum is imported from an STL file. When I run this, I get the following warning repeatedly:

"WARNING: Dangerous build in triangle neighbor list."

Do I need to be concerned with this? Is there perhaps a problem with the STL file? I did notice that my spheres might be escaping the drum, but I need to double-check for a reason.

I could only find the following in the "fix_tri_neighlist.cpp" file:

//if a fix move/mesh/gran is registered, advise the user to increase skin safety (and eventually shorten time-step)

Hi everyone,

I added this command in my file in order to move the top wall:

region topwall plane 1. 1. 1. 0. 0. -1.0 units box vel 0. 0. -0.1

I must define the interactions between the wall and the particles with this command:

fix wall1 all wall/region topwall gran/hooke 1.0 1.0 0.002

But I think that there is an error on the type of interaction (style). How can I define these interactions ?

My second question is: How can I get the normal force applied on the top wall or directly the normal stress ?

Regards
Jf

Hi everyone,

I would like to know, How I can integrate the position of spheres into my simulation ?
I have ready created a sphere packing and I want to use it.

I know that I must add this line into the fle in.mysimulation
# Read data

read_data position.sys

The file position.sys need to be writen like that ? (look the line under)
Please, can you correct ( position.sys) it in order that it works.
Thanks
Regards
Jf

LIGGGHTS Description

1 spheres # number of spheres

T atom types
# type of atom = granular ?