LIGGGHTS® - User Forum

Hi all,
I'm trying to run a 2D simulation. I'm using the 1.4.6 release.
I found 3 main problems:
- the choesion model doesn't work for 2D models. How is it possible to take in account it?
- the particletemplate/sphere + pour/dev/packing does not work with 2D analysis but only with 3D. So I switched to pour/legacy LAMMPS command. Is this wanted or is it a bug?

Hi all!
I am new to LIGGGHTS and want to simulate granular gas. As suggested by Christoph that LIGGGHTS can be used to simulate granular gas but the time-step has to obey the Hertz criterion.
But i dont know how to calculate the value of time step which obey the Hertz criterion especially with vibrating boundaries.
If somebody can help me or guide me, i will be thankful. I am not finding a proper way to calculate time step value.

Maz

Dear All !
I have a basic question " can LIGGGHTS be used for the simulation of dilute granular media i.e. especially for the granular gas?" if yes, is there some special limitation about time step or some other limitations ?

Anyone help, i will be thankful.

Sajjad

Hey

I wanted to rotate a mesh using the fix/mesh/gran, but I didn't want the rotation to be instantaneous. Is there anyway to define a spin up dw/dt until it reaches the desired w? I'm pretty sure there isn't but thought I'd ask?

One work around would be to alter the rotation every few timesteps, but this would be clunky, and would make for a messy input file. So, assuming this capability isnt there, how easy can I program this in, and where can I do it?

Jay

I can not build this last version of liggghts. even if making in serial manner I keep getting :
/usr/bin/ld: cannot find -latc
what is wrong with this new version?

Hi everyone,

I'm using if and label command to generate loops in a script. I'm using the fix ave/time command to write data to a file each time running through the loop. What I want is to write data into a file every loop. But this command replace the data in the file created in every loop time. Are there any methods to add data to a file rather than replace the data in each loop?

Thanks a lot

J. Wang

Hi Friends:

I almost read the documentation of the LIGGGHTS and I'm somehow getting familiar with the commands. I would be thankful if you can help me in fix deposit command.

I followed the pour_dev example to create my own input script, but the output are unacceptable.

What I'm going to do is to pour 1000 particles in cylindrical container (we have boundary interaction with particles) ; and in every pre-specified step, I want to calculate the void ratio (porosity) of deposited particles.

In the LIGGGHTS documentation, it explains how to use

fix ID all property/global gamman peratomtypepair ... and
fix ID all property/global gammat peratomtypepair ...

to set the normal and tangential viscoelastic damping constants. It also talks about a gamman_abs and gammat_abs alternative to that fix.

However, I cannot seem to set them myself in an input script. The function "deriveContactModelParams" in pair_gran_hooke_history.cpp seems to override any settings I want to make.

A snippet of my contact parameters section looks like this:

Hi everybody,
Is there a easy way to dump the six components of virial stress.
As far as i know, following commands to be used for determining contact forces are not working properly.
1. pair/gran/local
node/601
2. stress/atom
node/361
regards,
Samantaray

Hi,

I am trying to simulate shear flow of soft particles with a given pair interaction. I have a periodic box. Is there a way to implement Lee's Edwards boundary in the gradient direction ?

Lee's Edwards Boundary condition : influence of shear on the periodic images is taken into account by shifting the periodic images according to the bulk shear rate.

Thanks,
Lavanya