LIGGGHTS® - User Forum

Has anyone developed a simple way to dump per-contact parameters such as maximum normal force per contact? For example, I would like a file that stored time of contact, location of contact, and max normal force.

I had this implemented in an old version of LAMMPS by creating a new pair style pair_gran__hertz_history_stats and by expanding LSHEAR and shearpartner in fix_shear_history.cpp, but these changes generated some interesting segmentation faults.

cheers,
Scott

Hi all,

After a long period without playing with LIGGGHTS, I come back and I want to re-install the code.

I follow the nice explanations to install the code from Git. I built the code and I obtained an executable lmp_fedora in the src file.

I try to run an example:
~/myliggghts/examples/LIGGGHTS/conveyor$ ../../../src/lmp_fedora < in.conveyor
LIGGGHTS 1.5 based on lammps-10Mar10

And nothing in the post folder !!!!

Please anyone, can tell me what I am doing wrong.

Thank you for your help.

Hi Somnath,
Here is dumpfile.
Thanks,
Ram

hi, everyone
I have a puzzle in the using of periodic boundary condition in the setting of particle flow.
the simulation box is cubic ( x:0~0.1, y:0~0.04, z:0~0.1).
I want to take a periodic boundary condition in the y direction, I dealed with it with the following steps:
firstly pour the particles and the related settings is:

boundary f f f
fix xwalls all wall/gran/hertz/history 1 0 xplane 0. 0.1 1
fix ywalls all wall/gran/hertz/history 1 0 yplane 0. 0.04 1
fix zwalls all wall/gran/hertz/history 1 0 zplane 0.0 0.1 1

Hi Christoph,
I have seen discussion in the forum about reading and outputting the contact forces between particles using compute pair/gran/local and the dump local command,
but I notice the compute pair/gran/local command can only output f_x, f_y and f_z respectively,
can I possibly output the normal contact force? If yes, how?
Also, I know that the current pizza can't convert the dump file of this compute to .vtk file, is there any method to do the conversion?

Thanks in advance.

Hi Christoph,
Following your reply in a post "how to speed up DEM"
I have taken a look at my timing statistics, and it seems the "other time" takes up the most of the time consumed.
Pair time (%) = 312.239 (32.578)
Neigh time (%) = 9.10633 (0.950124)
Comm time (%) = 16.8501 (1.75809)
Outpt time (%) = 0.128907 (0.0134498)
Other time (%) = 620.111 (64.7004)
Do you have any idea what is the "other time", How do I reduce it?

Hello all. I am fairly new to LIGGGHTS and I have been trying to run a very simple simulation of two spheres in contact under load by method of compaction. I am simply using two .stl walls (bottomwall and topwall) and compact the two spheres my moving the topwall and keeping the bottomwall constant. I am able to view the simulation in paraview and I see the top wall moving; however there is absolutely no interaction with the particles.

My input file:

Hi LIGGGHTS users,

I want to do some simulation in order to validate the CODE with my experimental data. My experimental findings are related to static granular packings in which radius of particles are varied from 0.1mm to 16mm. I used this command to check time step but i get different values for different diameters:

fix ts_check all check/timestep/gran 1000 0.1 0.1

For example this warning is printed during simulation, the value is constant for one kind of diamtere.

WARNING: time-step is 31.483188 % of rayleigh time

Hello.
I have a question about the normal dissipation force model for gran/hertz/history pair_style.
From LIGGGHTS documentation and source I see what

F_dissipation = -gamma_n * relative_vel_n

where

gamma_n ~ (S_n*m_eff)^(1/2),
S_n ~ Y_eff * (R_eff*delta_n)^(1/2).

So,

F_dissipaton ~ (Y_eff)^(1/2) * R_eff^(1/4) * delta_n^(1/4).

But as I know, and as follow from ref.[Brilliantov] (see eq.(17)) from the manual, it should be:

F_dis ~ Y_eff * R_eff^(1/2) * delta_n^(1/2).

Whence is this discrepancy?

I'm interested in simulating magnetic particles in a media. How can I add this force as a source term in liggghts, which force can be derived analytically, f(x,y,z) or
solved by a FEA solver. For simplicity, I neglect a dipole-dipole effect between particles. Thanks in advance for your guidance.