LIGGGHTS® - User Forum

I am trying to simulate a suction action using a dynamic region and fix addforce. The problem occurs that the dynamic region moves partially, but not the entire length of the simulation region. I am using the variable function ramp, over 100k time steps, but it looks to be only evaluating it over 20k steps.

I am using LIGGGHTS 3.1.0.

Any help is appreciated.

-Scott

Dear liggghts users,

I use hertz contact model to simulate the sandy soil and the young's modulus is 20e9 for sand. But the contact force is so large with this 20e9 modulus so that it keeps telling too many neighbor bins message. So I am thinking to use a very small timestep. Here comes to problem, if I use small timestep like 1e-8 or 1e-9, the simulation is time consuming. So what can I do to enhance simulation time and make the simulation no error by that I mean reasonable?
Hope anybody could guide me!!! Deeply appreciated!!

Best wishes
xiaobaishu

Hi all,

Few simulations of mine will take even a day or more to finish.
When I am trying monitor the storage space on my hard-disk then it is being filled like 10GB/hr approximately but my post/directory is only 1GB .

Is LIGGGHTS writing some temporary files while I am running the code and kills those files after the simulation is DONE ?
This is a serious problem for me, as I am not able to launch multiple runs and if the run is for longer duration, CODE assumes as if there is no space to write DUMP files and gets killed.

Please help.
Thank you.

Hi,

While inserting 2 particles with different diameters in a container, the particles distribution based on number was not proper. I would like to know how can one change the particle distribution value in number for better insertion.

Regards
Hari

Hi

I am trying to insert 45000 particles in a model. But while running the program for 1000 timestep, it was found that the whole particles get inserted in the first timestep itself. How should I change the program to get to deposit equal particles in equal timesteps ? Where could I have made an error?
I am attaching my input deck along with the model and insertion face.

Regards
Hari

Hi

Is there a way to find the normal vector to the wall at the point of contact(particle-wall contact) ?

Thank You.

Hi all,
I going to insert very high particles in bed of channel. But inserting of particles in a large region is very time consuming. Can I use inserted particle in small region for fill a larger region? how do I expand these particles to the total region?

Thanks
Elham

Hi everyone,
I am now working on the simulation of Janssen effect with Liggghts. The command I used in the input script is
"stress/atom" , no keywords is attached after this command. (The keywords attached can be ke,pair, bond,angle, dihedral, improper, kspace, fix, or virial ).
A packing is simulated in a cylinder with 20 0000 granules.

My liggghts always works, but today when I changed Young's modulus from 5e6 to 20e9（I am using Hertz model to simualte sand particles）. It stays at step one and there is no error message. I waited a long time, it;s still at step one. Can anybody guide me ?Appreciate it!!

Thanks
xiaobaishu

Hey guys,

I try to do the hopper tutorial. Therefore I take following code :

# Import mesh from cad:
fix cad1 all mesh/surface file meshes/hopper.stl type 2 scale 0.001
# Use the imported mesh as granular wall
fix geometry all wall/gran/hertz/history mesh n_meshes 1 meshes cad1
# Create stopper for funnel
fix stopper all wall/gran/hertz/history primitive type 2 zplane0.0
# Define the physics
pair_style gran/hertz/history
pair_coeff * *