LIGGGHTS® - User Forum

Hi

I'm new using LIGGGHTS.
I'd like to simulate a sand glass with LIGGGHTS. It works quite good for now, but i need a usable value for my sand's friction.

fix m4 all property/global coefficientFriction peratomtypepair 1 ??

If i had a Ra value, would it be possible to assess or even to compute the friction of my sand? (see the SEM picture)
Or has someone experience in simulating sand and knows a usable value?

something else:

Hello,

I am a user of LIGGGHTS and I am applying a high pressure (10% of the Young's modulus) through a servo wall.
After some time I have the loss of particles (from 10 to 100 out of 12000), but the simulation runs well for more than half its duration.
Why there is this problem? Is it solely due to the choice of the timestep?

I am choosing a timestep suitable for my properties, indeed I am doing a check and it is always positive and the simulation runs without problem at the beginning.

Thank you and have a nice day,
rob1

Hello LIGGGHTS users,

I'm trying to set up a heat source which changes with time. The documentation suggests that it should be possible to set up a time and/or space-dependent heat source by using the set command and using an atom-style variable. Space dependence works for me, but time does not. Below is a simple example of how I specify a time-dependent heat source:

variable H atom step
set atom * property/atom heatSource v_H

Hi everyone,

I am a new user to liggghts and applying the packing problem in the examples to practise. In a case, I want to know the equivalent, or saying apparent, pressure of the packing system in x, y, z direction. I find that in the thermo_style command the pij may give the quantity. however, in the source code, it doesn't have those option actually, resulting in a error when I add them as the keyword.

Can anyone suggest me how to get the equivalent pressure or force for a packing in xyz directions.

Thanks
Weijing

Hi there, I've been experiencing a little bit with LIGGGHTS for the last weeks. I could get the software installed and running. The tutorial and the test cases available were of great help.

Right now my "problem" is how to run a simulation parallelly. I'm aware of the "processors" command and made this change to one of the input files I'm handling:

processors 2 2 2

Besides that, to launch LIGGGHTS I issue this command:

$ mpirun -np 8 /lmp_fedora -in input_file

So, is it enough to get the simulation running parallelly?

I've been looking for some documentation on the "characteristic" velocity used in the Hooke contact model. I have a simulation that is essentially a hopper filling/draining problem, but I also have the particles fall on and impact different surfaces once they leave the hopper. Thus, I have 2 different characteristic velocities in my simulation:

1. The very low velocities present in the hopper
2. The relatively higher velocities the particles have when they strike the surfaces outside the hopper.

Hi All,

I am doing some hopper flow discharge simulation of granular material. The hopper is fitted with a "stopper" at the discharging outlet. I want to periodically open the stopper (translation motion) from closed position to fully open within say 10 seconds of simulation time.

Which command do I use to allow the "stopper" fix to open periodically.

I look forward to your help.

Regards,

Theo_Score

Hallo,

in order to use the fix bond/create and fix bond/break command for my bond model i need the MC package, which is not available in LIGGGHTS-PUBLIC version 3.5 . Therefore, i have copied the MC file from LAMMPS (17 Nov 2015) stable version in my LIGGGHTS-PUBLIC src directory and tried to compile it using the command make g++. When i tried to compile it it gave the following error:

Hello,

I have coded an algorithm to generate multi-spheres to describe the shapes I need.

The problem I have now is that, since the spheres generating the multi-spheres are in the order of microns (10-60 microns) and use units SI, when I try to run the LIGGGHTS script I get the following error:

ERROR: Fix particletemplate/multisphere (id pts1): Volume expectancy too small. Change 'volume_limit' if you are sure you know what you're doing (../fix_template_sphere.cpp:447)

Hi,

Why Fix wall/gran and pair/gran allow only one compute of type wall/gran/local and pair/gran/local ???
I want to have normal contact force, tangential velocity and contact length (history) of a contact, simultaneously.

Hossein