LIGGGHTS® - User Forum

Hi all

I've been reading the manual in order know how to speed up the simulation. If I increase the number of processors to running the simulation I'll be able to reduce the pair time. is it the best solution to achieve my aim?
Can anybody tell me the steps that I have to follow?

best.

I'm having a frustrating issue at the moment. I set up a simulation (at the moment with basically no particles), and then import an ascii stl mesh (produced in meshlab) with the following line:

fix MT all mesh/surface file MT.stl type 1 rotate axis -3.832567 0.000000 2.832567 angle 17.365650

When I look at the output, the mesh has rotated, but it has also become larger. Am I doing something wrong here, or is this a bug?

tar attached containing full input script and original stl mesh.

Attached is a little Fortran code for calculating the center of mass and moment of inertia for a clumped particle.

Regards,
Chris

Hi,

is it possible to calculate and dump the center off mass for clumped particles ? I tried compute com/molecule and varius dymp-styles but without success. Or is there a post-prozess option in pizza ?

Thanks,
Christian.

Hello, Christoph,
I try to use the latest version of LIGGGHTS 2.3.2, but it doesn't work. Then I tried with an example from Liggghts - meshGran, and it doesn't work either. I uploaded the output and error meassage files. Could you take a look? Thank you!

Hi everyone,

I'm confusing with cohesion energy density in the pair_gran_hooke_history. As I understand cohesion energy density is the work needed to separate the whole volume of particle in contact. So how to calculate cohesion energy density if Van der waals adhesion is taken into account? And where is cohesion energy density in original JKR model?

Many thanks for your help!

Best regards,

Duy

Has anyone ever made an atom property (or assigned it to a region, changed its type, etc) based on a conditional statement?

For instance, if I set some threshold of particle force, say...
variable crit_force equal 50
then i find per/atom values of force magnitudes
variable mag_force atom (fx[i]^2+fy[i]^2+fz[i]^2)^0.5

from there I'd like to say something like...
if "${mag_force[i]} > ${crit_force}" then &
[set the atom, i, into a group, change the atom to type 2, etc.]


We are often asked what kind of computer is needed to do DEM-Simulation with LIGGGHTS.
I used every computer system in my local area to make a little benchmark.
All tests where done with the moving mesh example script** and Liggghts 2.2.3.

The Linux machines are running Ubuntu 12.04.1 LTS with mpich2 and GCC compiler.
The Windows 7|8 machines are running mpich2 1.4.1 and a cross compiled windows version*** (VS2008 compiler).

I've created a couple of small tools for generating STL files for some simple geometric constructs that I wanted to share in case anyone finds this useful. Basically, I got sick of going to a CAD program every time I wanted to create a simple regular frustum, rectangular bin, or simple plate. The attached codes are written in Fortran. Hope someone finds it useful.

Regards,
Chris

Hi, All:

I currently have a problem that needs to consider the position and number of particles with different sizes, so basically I am trying to calculate the porosity of the poured grains. For this target I need to know number of particles and the height of poured grains, so that I can calculate this property.

I am wondering if there is any existing examples using LIGGGHTS that can:
1. calculation of porosity
2. if there is not such a function, so how can I access (for example with python) some properties of particles after pouring