LIGGGHTS® - User Forum

Dear LIGGGHTS users,

I want to apply a constant pressure on the top wall and let the bottom wall being frozen.
Could you please tell me the appropriate command to achieve this?

Thank you in advance.

Best wishes,
June

Dear LIGGGHTS uses,

I am now simulating a system with millions of particles . Can GPU acceleration be used for LIGGGHTS?

Thank you very much.

Best wishes,
June

Dear LIGGGHTS users and developers,

I am trying to create an intial packing strucutre of three different size particles: 1, 10, 50. The numbers of particles are 100 (D=1), 10 (D=10), 3(D=50) and the initial volume fraction is 0.15. I have tried two insert command:

1. fix ins all insert/pack seed 32452867 distributiontemplate pdd1 vel contant 0.0 0.0 0.0 insert_every once overlapcheck yes all_in yes
particles_in_region 113 region bc

Hi
I am currently using LIGGGHTS-flexible fiber version.
My problem is somewhat similar to the shear box tutorial. I first create fiber templete by bonding the spheres; bonds and atoms are of type 1.
After fiber -fill in a space and depositing them onto a plate, I want to bond those fibers whose separation is less than a critical value. I want to create a bond of type 2 for inter-fiber bonds.
Since I have atoms of type 1 through out, how should I ensure that atoms are bonded with bond-1 within a fiber, however, with bond-2 inter-fibers (cross-link).

Hello
So far, i am able to generate fibers in random orientation using LIGGGHTS-flexible fibers.
However I wish to generate fibers with a preferred orientation, i.e. fiber crientation should follow a probability distribution of the form: f(theta)= 1/pi -A*cos(2theta). Whare A is a user defined parameter (=0 for random distribution).
Is there a way to implement above in liggghts

Thanks
Shubham

Hello
I am currently using LIGGGHTS-flexible fiber version
For my research needs, I have to make changes in the granular bond model (may be bond_gran2) such that it also incorporates elasto-plastic effects.
Unfortunately, I am not very fluent in C/C++ , however, I can code in python environment.
Is there a way that I can write my custom code code in python and run it with LIGGGHTS?

Hi,

I am performing a biaxial compression simulation where I have a granular array surrounded by 4 extremely large granules to mimic a wall. In this simulation, I start off by fixing the left and bottom "walls" (big granules) and compress the array by adding a force (fix addforce) to move the top and right wall to compress the system. The force I use is to get a desired pressure in the confined state. Up to here all is good. I get a stress state which has the desired pressure. I add viscosity to dampen out the kinetic energy.

Hi,
I hope you are doing great.
Let's assume I have a dump called mydump, that prints the system state every 40 steps.
Later my system evolves and stops if a given condition happens (I use an if inside the run command). Many times this stop happens at some intermediate step, not multiple of 40, so the last system state is not dumped with mydump.
Can I call the dump command explicitly inside the if? right now I am just copying the full dump inside the if and using a write_dump, but this duplicates a lot of instructions than are difficult to keep in sync .

Hello
I am relatively new to LIGGGHTS-Flexible fiber version. I was going through the tutorials about using the restart files.
I some tutorial folders I found: main LIGGGHTS file, read_restart and write_restart files.
Can you please let me know (or direct me to a place where I can learn) about the meaning and how to use these different kinds of restart files.

Thank you very much

Shubham

Hi all,

1) Could you please explain the meaning of output of the following commands:
compute cpgl all pair/gran/local pos vel force (https://www.cfdem.com/media/DEM/docu/compute_pair_gran_local.html)
and dump dmp3 all local/gran/vtk 200 post/forcechainvtk*.vtk cpgl (https://www.cfdem.com/media/DEM/docu/dump_local_gran_vtk.html)?