LIGGGHTS® - User Forum

Hi,

We're using LIGGGHTS to study a problem in materials handling for the minerals processing industry. Particles enter into a rectangular containment vessel from several defined feedport regions near its roof - this is to simulate material flowing into the vessel through feedports from storage hoppers above (for various reasons we don't want to model the particles inside the hoppers themselves). The idea is that the vessel slowly fills up with particles until they physically block the feedports, at which point the feed rate into the vessel slows down or stops ("choke-fed" condition).

Hello Christoph, I would like to include a flag that changes its state when a particle touchs for first time the wall. This is like the:
touch = firsttouch[i];

in the pair_gran_hooke_history.cpp compute function. I want to see when the contact is lost in order to make some variable assignments. So in: void FixWallGran::post_force(int vflag), I can modify the code and make something like:

if (wallstyle != MESHGRAN_FWG){
rsq = dx*dx + dy*dy + dz*dz;
if (rsq > radius[i]*radius[i])
{
if (touch[i]){
touch[i]=0;

I encounter difficulties in running a 2D simulation. A rigid rod consisting of 200 atoms is attached to a spring. The rod should only move in the xy-plane. Therefor I put 'dimension 2d' in the input file, then setup a simulation box with a small z-dimension with periodic BCs in z and fix enforce 2d. The atoms are treated as a rigid rod via the fix rigid command with force components in x and y direction and torque around the x-axis. NVE integration should be done with fix rigid.

Although I apply a strong spring force, the rod doesn't move at all?

Dear Sir/Madam

I am a beginner to LIGGGHTS. I have installed ICC, OpenMpi, FFTW, PARAVIEW and LIGGGHTS in my Ubuntu 10.04 Lucid platform.
Please guide me to get started with LIGGGHTS. How should I proceed. At some beginners tutorial should be provided.

Please help.

Rahul Kumar Soni
Indian School of Mines
India
http://sites.google.com/site/ismrahulsoni

Hi, Christoph, i have a question about the difference of pair_style in LIGGGHTS and LAMMPS. As LIGGGHTS manula discribed, the stiffness and damping coefficients in LAMMPS are now derived from the material propeties (e.g. Young's modulus, poisson ratio).

Hi,
Is it possible dump forces on stl?
I'd like to save a dump file to then create with pizza a surface vtk file with force field (like a patch).

Thanks for any reply

Andrea

Hi,
I'm new with LIGGGHTS. I tried the tutorials and they are very good but I found only granulars that move from an inlet to grond (or to outlet).
How can I set instead fixed granular on a plane like a ground?

Thanks for any help

Andrea

Hi all,

In the discrete element method, the normal contact between two spheres i and j has the same direction than the n-axis (in the local reference (n,s,t)).Thus, it is possible to compute the angular orientation of the particle "i" following the s-axis and t-axis (tethai_s and thetai_t) in the global reference (x,y,z).

To compute tethai_s and thetai_t in the global reference (x,y,z), I do:

thetai_1 = omega[i][0] * dt;

thetai_2 = omega[i][1] * dt;

thetai_3 = omega[i][2] * dt;

Hi all,

I am trying to restart a heat transfer simulation. I failed and thus I created a smaller problem, where I have the same problem, using the example heatTransfer_2. Please find two input scripts for liggghts below: in.heatTransfer and in.restart. in.heatTransfer writes a restart file after it is done integrating and then in.restart reads the restart file. Visualizing the output with paraview showed that the temperature is not read from the restart file.

Could you tell me, what I am doing wrong?

Hi Christoph,

I saw that the commands : read_restart and restart can save and reload a simulation.
However, I would want to know if these commands also save and reload the values held by the array "shear" (contact history).

Regards
JF