LIGGGHTS® - User Forum

Hello,

I am using the LIGGGHTS Flexible Fibers package in my work. In the Potyondy & Cundall 2004 paper where they introduce the parallel bond model implemented in LIGGGHTS, they describe a methodology (Appendix 1) to compute stress in the body arising from the bonds, which should be the same as the compute stress function in LIGGGHTS. From my experiments, it doesn't seem like the bond stresses are factored into the LIGGGHTS compute stress. This brings me to two questions:

Hello. I am working on the effect of magnetic force on the particle compaction process. I am using the following Github repository for the implementation of magnetic force:TJLeps/LIGGGHTSwMAGNETICS: official release of the LIGGGHTS® DEM software, by DCS Computing GmbH. For further info, forums, and bug reports, please visit which takes into account the mutual dipole interaction of the particles. In my simulation, I am using superquadric particles. The case runs okay in a single processor, but it does not run in multiple processors.

Hello everyone,

I am fairly new to LIGGGHTS and have started by creating a simplified case. I exported a .csv file from Paraview containing the x, y and z positions of particles (spheres): I wrote a small Python script to grab these coordinates and some other necessary information and create a .data file with the minimum amount of necessary information (sections --> head and body). I know that I need to use the read_data function in my initialiser file, which I have called in.liggghts_run.

Hi everyone,

I am going to simulate granite using LIGGGHTS-with-bonds with particles of different radii. I need a dense packing of particles. When I used fix particlestemplate/sphere in LIGGGHTS to fill a desired volume, even with a very high volume fraction, there was still a lot of void space between particles, and they were not in contact at all.

I am doing simulation of heat transfer in granular powder particles that are falling (Ex. in.chute_wear) but after simulation temperature values are significantly as high as 10^15 magnitude without applying any additional heat source and simply applied NVE integration . I think these values are unrealistic how to decrease this temperature values so that it resembles realistic scenario and how these values are computed under the background???
I will provide input script and output values on the terminal pls somebody guide me and help me to resolve this issue.

Hello LIGGGHTS team,
I have generated a compacted bed of multi-sphere (clump) particles in YADE (it is a bed of soil particles with specific particle shape distribution). So I have their exact coordinates, members, and sizes in a txt file. Is there any way for LIGGGHTS to generate my bed by reading each sphere location and radius and then the clump it belongs to?
I have tried two approaches and I have failed so far:
1- Using create_atoms, have atoms of the same clump in a group and then use fix rigid for each group to make them rigid as a clump.

I have a question about the damping coefficients \gamma_n and \gamma_t in the Hertzian granular contact model, as documented in https://www.cfdem.com/media/DEM/docu/gran_model_hertz.html . Where do these come from? Can somebody provide a primary source or derivation?
Thanks and best regards

Hi there,

During a scratch simulation which consist of conical tip and flat specimen, should i update ensemble(nve/sphere) after increasing force statement of tip ?

I would like to simulate a scratch simulation in micro scale, which tip and substrate make a contact and slid (constant velocity).
And during the sliding process i want to increase a normal load for tip ( E.G, 1 mN to 100 mN).

I am a beginner in using LIGGGHTS and I am currently working on calculating the fabric tensor for my simulations. I noticed that LAMMPS has a dedicated compute fabric command for this purpose (https://docs.lammps.org/compute_fabric.html). However, it seems that LIGGGHTS does not have a similar command.

Could anyone please advise on how to calculate the fabric tensor in LIGGGHTS? Are there specific procedures or workarounds available for this?

Thank you in advance for your assistance.

I am trying to replicate a box including spheres and multi-sphere particles with periodic boundaries. When try to run the model after replicating, I get this error "ERROR on proc 0: Internal error in multi-sphere method (../multisphere.cpp:472)". Note that when I removed the multi-sphere particles from the model, the error disappeared. When I made the boundaries non periodic, the error still occurred. Here is a minimum working example:

atom_style sphere
atom_modify map array sort 0 0
boundary p p p
newton off

communicate single vel yes