LIGGGHTS® - User Forum

The particle clump is made up by some overlapping spheres ,I have confirmed that the volume and mass can be caculated correctly in liggghts. Now I wonder IF THE INERTIA TENSOR CAN BE CACULATED CORRECTLY ? since it is concerned with shape and density distribution. It says the caculated inertia tensor is based on the mass center of the clump, does that means the coordinate origin is moved to the masscenter automaticly ,or should I give the spheres locations based on mass center ?
PS: does anyone knows how to find the masscenter of a irregular shape clump using MATLAB?

Hi,

I am trying to simulate mixing of two different particles (the small one is 5 micron and the large one is 100 micron) and also the simulation domain is in the order of a couple of centimetre.

Greetings,

Is there a way to LIGGGHTS could register the real time of a full simulation?

Thanks,

Nicolás.

Hello,
I am a new user of LIGGGHTS and I am simulating a shear cell with:
- upper surface as servo, to apply a force in y direction
- lower surface moving in x direction
- fixed walls in the z direction
- boundary p f f
All the surfaces are imported as STL files.

The first question is about the [compute multisphere command], since I know the properties of the given multisphere template have been caculated by Monte Carlo method before the simulation, I have tried to use the [compute multisphere command] to get the properties. I add the [compute dens all multisphere property density] to the given example "multisphere_stone_restitution". But there is always an error : invalid compute style. I want to konw why this simple command does not take effect. Does any body have a simple example to show me ?

Dear LIGGGHTS user,
I have tried the example of mesh/tet which create particles from a imported tet-mesh data. i.e.
"region mesh mesh/tet file data/test.vtk scale 1. move 0. 0. 0. rotate 0. 0. 0. units box"
This example create one timestep output only. Although I enlarged the run time and more output, but I can't find any change during the whole running. The question is:
If I want to use the particles created by the mesh/tet method as a initial pack of particles, want release these particles and let them flow, is this possible?

Dear LIGGGHTS users,

From the LIGGGHTS-Manual I understand that the limitation of the tangential forces through the Coulomb criterion Ft = cof*Fn is applied only to the tangential spring force and not to the tangential damping force. For example in the documentation for the pair_style "gran" it says:

"The tangential overlap is truncated to fulfil F_t <= x_mu * F_n"

Or in the documentation for the model "tangential history" it says:

Dear LIGGGHTS users,

Hi,

I am very new to multisphere model. I would like to know,

1) Is their a way to model two or more different "types" of particles in a single clump?
2) How can I model in different shapess?

Thank you.

Hey,
is it possible to set a variable to atoms in a group? So that for example all atoms in group 1 have have a atom variable that is 1 and for group 2 the same variable has the value 2 for each atom?
What I'm trying to do is subdivide the simulation region in many groups and calculate the density in these groups. But now for post process i want to set an atom variable which defines the density of each groups and all atoms in one group shall have the same density value.
Is this possible?
kind regards
joshua