LIGGGHTS® - User Forum

Can anyone help me understand the rotation of shear displacement in LIGGGHTS? The update of shear[0] += vtr1*dt is fine, but I am bit confused with shear[0] -= rsht*deltx. Why has it to rotate and why it is a minus?
Many thanks.

(Problem solved)

Hi All,

I am not sure why, but when I compile the LIGGGHTS 2.0 RC code I have had the fix_wall_gran file replaced with an older version that does not include "unregister_compute_wall_local". Perhaps someone has an idea why this happens. I have posted the error I receive when compiling.

compute_pair_gran_local.cpp: In destructor ‘virtual LAMMPS_NS::ComputePairGranLocal::~ComputePairGranLocal()’:
compute_pair_gran_local.cpp:102:17: error: ‘class LAMMPS_NS::FixWallGran’ has no member named ‘unregister_compute_wall_local’

Hi I've created a simulation where a small fraction of the overall number of particle in the simulation experience a large force relative to the other particle in the simulation. Does anyone know if it is possible to get LIGGGHTS to count the number of particles experiencing a force greater than say fior example 10N? I guess this could be done using a logic statment but i'm not sure how to go about it.

Hello all,

I am generating a txt file for the read_data command and I am getting an error that I just cannot figure out! If someone could be so kind as to take a look at this for me, it would be very much appreciated.

My input file is the following:
##
units si
atom_style hybrid granular molecular
boundary f f f
newton off
communicate single vel yes
read_data read_data.txt
mass * 1.0

###################################
# no boundaries for now...
fix 1 all gravity 9.81 vector 0.0 0.0 -1.0
fix 2 all rigid molecule
neigh_modify exclude molecule all

I am a fresh user of LIGGGHTS just trying to install the program today. I have downloaded the liggghts package via git including the lpp (git clone git://cfdem.git.sourceforge.net/gitroot/cfdem/lpp mylpp) but just can't get any example started after this stage. Do I still need to do a sudo-apt get install before i can get it working? Please help

Hi everybody,

I'd like to calculate the hydrostatic pressure in a cylinder filled with granular particles on its cylindric wall.
I think the command

fix xxx all mesh/gran/stressanalysis xxx.stl ...

is not an appropriate measure to calculate these forces, because by outputting the forces on the mesh with f_xxx[1], f_xxx[2], f_xxx[3] I get the total forces in these directions. That means I get the sum of positive and negative forces and the result will be somewhere near zero...

How could I proceed instead?

Thanks in advance,
kind regards,

Hi, everybody

I'm new liggghts user,
I need to create a planar face for the fix insert/stream but i dont know what are the specifications for making the insertion face

Hi Christoph,
I want to compress the particles after they are poured completely in a cylinder. But the moving wall does not affect the particles and it move through the particles means particles are not resisting the moving top-wall. My input script is:

atom_style granular
processors 1 1 1
atom_modify map array
boundary m m m
newton off
echo both

communicate single vel yes
units si
region reg cylinder z 0.0 0.0 0.07 0.0 0.751 units box
create_box 1 reg
neighbor 0.001 bin
neigh_modify delay 0

#Material properties required for new pair styles

Hallo to everybody,

right now I'm trying to verify experimental results of a so called "uniaxial compression test". In this test, a present pebble bed is compressed by a slowly moving wall until reaching a specific strain rate (1,25 % in this case). While compressing, the effective force on the wall is measured.

These results have already been verified using another DEM-Software.

Now I'm trying to verify these results using LIGGGHTS. My results highly deviate (about factor 300) from the existing verified ones, though.

Hi,
Does anybody have an updated version of restart2data tool?

After using 1.5.2:
pair_style gran/hertz/history 1 0 #Hertzian without cohesion
pair_coeff * *
write_restart restart.chute3DPBC_init

I get the following from restart2data:

Reading restart file ...
WARNING Restart file version does not match restart2data version
restart2data version = 15 Jan 2010
ERROR: Unknown bond style ?ctive