LIGGGHTS® - User Forum

Hi,

Hi Chris,

My question is pretty much same as the title. To explain in more detail (please also take a look at this post: http://cfdem.dcs-computing.com/?q=node/1745 ), the following command is used to insert particle steam:

fix ins nve_group insert/stream seed 5330 distributiontemplate pdd1 &
nparticles 20000 particlerate 8000 overlapcheck yes vel constant 0.0 5.0 0.0 &
insertion_face inface extrude_length 0.02


Hi,

I am working on a shear cell simulation. I run the simulation in different steps (filling, cleaning, shearing...). The problem is that after I finish the shearing operation, I noticed that I have not attained steady state for the shear force. I want to restart (this is the 3rd restart that this model will see). The model will not restart from this point. I have included all the files needed to (try to) run my model. I get the following error:

hi everybody,
I was wondering if there is any way of calculating cumulative rotation of particles through the scripting. I do not want to change the source code and I think that its postprocessing will be so time consuming as particles data should be saved in all steps. moreover, I need to know which particles slide against their neighbors. how can I overcome these problems?

thank you so much
mojgan

How to calculate the forces acting on a geometry in LIGGGHTS? I need to sum up all the forces acting on all of pieces of my mesh. any help is appreciated.

Hi,

I need the average weighted pressure of the particles. Using compute pressure and compute reduce of compute stress/atom I get the same result. In Liggghts this formula is used:

I am looking for something like:

using

What is the pressure Liggghts calculate with compute pressure? Why does it differ from a the pressure on the walls of the particles? Can anyone please give a hint?

Regards,

Paul

Hi,

Hi,

I just want to say there is a new Voronoi package for Lammps by Daniel Schwen. It supports now polydispers packings, calculation of the cell surface and much more. It's already included in the Lammps git repository. You can install and compile in Liggghts without major problems, but the delivered vorotest script has to be changed, Liggghts doesn't support inline variables and the abs() function for variables yet. Done that, the tests should run without any error.

Regards,

Paul

Hi,

I need the average pressure between the particles. I tried two ways with exact the same results. compute pressure for all atoms using the temperature from a compute temp and compute stress/atom for every single particle and sum these with compute reduce. What would be faster? Is there a difference in speed between compute reduce sum and the variable sum() command?

Regards,

Paul

Hi,

I want to generate a dense packing with fix insert/pack and particle growing. This is very common and no problem with fix adapt. The growing ends when the particles have a reached a given pressure. The pressure is calculated by compute pressure. Since I have a lot of particles and slightly CPU I wonder if there is something new in interrupting a run when a special event occurs to save CPU time? Or is run N every n, check with if and going on else dump results and quit still the preferred solution?

Regards,

Paul