LIGGGHTS® - User Forum

Hello everyone,

If one tries to find official installation instructions for liggghts and goes through the CFDEM website, i.e., LIGGGHTS --> Installation, then this leads to "https://www.cfdem.com/installation". On this website, a link to the official documentation is provided. However, no relevant information can be found in the linked part of the documentation [1].

It would be great, if there was actual, official information about liggghts' installation.

Dear all,
I am doing a research on triaxial test in soils. In my simulation, I have two process, i.e. consolidation and shear process. I want to use the coefficient of friction f=1.0 during consolidation while use f=0.5 during shear process. I haven't found any command about changing this coefficient during simulation. Could anyone please give me a clue about how to realize this function?

Hello all,
I want to replace a large particle with two smaller particles if the contact force exceeds a fixed value (for simulation of particle breakage). Any suggestions how to do it?

I have used the fix break_particle in LIGGGHTS 2.3, but I could not successfully compile that version of LIGGGHTS in CFDEM coupling. So, I decided to find another way to simulate the particle breakage in a CFD-DEM simulation.

Regards,
Shahab

Hello everyone,

I am doing a simulation about triaxial compression test using Liggghts, and I am wondering if there is any command for us to obtain the instant porosity or void ratio so that we can output them into a txt file?

Any suggestion or clue is greatly appreciated!

Best regards,
Rachel

Hello,

I am trying to simulate the behavior of a shear cell and in order to do that I would like to apply a simulation environment reduction by application of periodic boundary conditions. Is it possible to use the Lees Edwards boundary conditions in LIGGGHTS? I read on the internet that this should be achieved through the use of fix nvt/sllod and fix deform but the fix nvt/sllod isn't there anymore, so what could I do in order to do that?

thank you in advance and best regards,

Hi,

i have setup a simulation with 6000 spheres using the "hertz tangential history" contact model and the atom_style granular. Each sphere has a specific radius, initial position and a my_val property (see below). my_val is related to the radius (external lookup table). After running 500000 steps, i change Youngs modulus from 5.00000e+006 to 5.10000e+006 using the fix-line below. In the next dump-file saved afterwards (501000), my_val and radius of 484 spheres (out of 6000) no longer matches.

Why?

Hello everybody,

I want to write out the sums of the forces in x, y, and z of all particles in a defined group at eveyr 100 steps.
So I create a region

region count1 block -0.7 0.7 -3.0 -1.5 0.0 0.6 units box

then I create a goup

group count1 region count 1

Dear all,
In fix heat/gran description has mentioned that:
h_c,i-j = 4 * k_pi * k_pj / (k_pi + k_pj ) * sqrt (A_contact,i-j)
However, based on the references, it seems that h_c,i-j related to the radius of contact circle. Thus, I think the formula should be like the following:
h_c,i-j = 4 * k_pi * k_pj / (k_pi + k_pj ) * sqrt (A_contact,i-j / pi )
Can you kindly tell me that I am right or is there another explanation?
Best regards,
Mohammad

Hi,

In my simulation, first I tried to add particles in the hopper < settle the particles< close the hopper with with a lid. While fixing lid I get an error :

ERROR: Fix wall/gran (id wall2): Unknown argument or wrong keyword order: 'wall' (../fix_wall_gran_base.h:131)

I am attaching my in.file below

Is it possible to fix wall twice?

Good afternoon
I would like to know which is the difference between running LIGGGHTS with lmp_auto and lmp_openmpi.

Thanks