LIGGGHTS® - User Forum

Hi my friends,

Are there anybody can explain a very basic question for me? In the document about the fix pour/dev/packing commad, it says:

vol values = fraction Nattempt
fraction = desired volume fraction for filling insertion volume
Nattempt = max # of insertion attempts per atom

What's the meaning of max # of insertion attempts per atom? Is it the maximum number of particles inserted in the box? What will happen if the maximum number of atoms have been reached but the desired solid fraction has not got yet?

Thanks.

Wang

Hi!
Is there some upper limit from the LIGGGHTS to the one and page values? If I increase the page value too much, I get memory error, when run is executed. If this is not an LIGGGHTS related, do you know is this Linux or hardware related issue? I'm using 64-bit Linux on distributed memory cluster with 8GB RAM on each node, and the LIGGGHTS is executed parallel in a distributed way.

Hi my friends,

I want to compress a packing by a specified force or pressure. Are there any command or code available now to control the force or pressure on a wall? Do I need write some extra code on LIGGGHTS to reach my purpose?

Thanks.

Jerry

Hi LIGGGHTS users,
Please anybody tell me if granular particles of LIGGGHTS are viscoelastic in nature? I mean we can transfer sound waves in the granular media.
Thanks,
A

Hi,

Does anybody know- is there any way to set the angular velocities of atoms to a specific value?
For velocities I can use fix_move and from a quick check I did I cannot find any similar option in LIGGGHTS as the rotate keyword does something slightly different.

Will I have to extend fix_move?

Thanks,

George

Hi,

I would like to model a viscous drag force (stokes drag) for a polydispersed simulation where the particle size distribution is specified using fix_particletemplate/sphere and fix_particledistribution/discrete. Since, all the particles have similar properties, I would also like to have one atom_type in the simulations.

In case anyone finds it useful here is some information about a method I use to couple Liggghts with a separate Lattice Boltzmann code written in Fortran.

The Fortran code is the driver, so it starts first calculates the fluid flow, writes the particle information to a file and then calls an external subroutine to run Liggghts automatically from the command line for one time step. See the following link.c file:

#include
#include
int dem_(int i)
{
printf ("Checking if processor is available...");
if (system(NULL)) puts ("Ok");
else exit (1);

Hy @ all,
I would like to calculate & print out the mass and the number of particles included in the calculation area.
I ´ve tried to use the following commands:
variable m equal mass(all)
fix extra all print 100 "$t $m" file out.txt screen no title "%step totalmass"

but I don´t know whats really calculated with this command.

It would be nice, if someone could help me,
Michael

Hi,
I got error when I use following commands in script:

compute 2 all stress/atom
fix 10 all ave/spatial 100 5 1000 z lower 0.001 fx fy fz density/mass density/number c_2[I] c_2[2] c_2[3] units box file vel.profile

..
.
.
ERROR: Fix ave/spatial compute does not calculate a per-atom vector
However, Fix ave/spatial takes input as per-atom vector.
Thanks,
Ram

Hi,
I want to simulate a quasi-static compression test for cohesive granular particles. In keeping with the quasi-static assumption I want to apply the total wall displacement in several tiny increments. After each increment the walls should be held in place and the particles should be allowed to reach equilibrium (that is the kinetic energy should go close to zero). Thus each displacement increment is to be followed by kind of a relaxation step. My question is how do I achieve this using liggghts?