LIGGGHTS® - User Forum

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

Hi All,

I want to use cohesion model washino/capillary/viscous for the simulation.

I have four different types of particles in the simulation. And, I want to apply cohesion to only two types of particles. For the remaining two types of particles, I want to apply only gran model hertz (without cohesion).

Can someone please help me, how to implement this?

Any help will be much appreciated.

Thanks,
Narendra

Hallo everyone,

since few days we try to install the current version of Liggghts on our Linux cluster (Ubuntu 14.04). The first steps were no problem, but we always get an error during the compiling process:

hey,
is it possible to do the immediate evaluation of variables for an atom-vector? For a scalar its simply
variable v equal vol
variable v0 equal $v
But for atom vectors it is not possible to use $
variable x atom x
variable x0 atom $x
this would fail.
Is there a way to safe the initial state of an atom vector and use it in further atom vector calculations?

kind regards
Joshua

Hi all!

I was looking into literature to find out more about coarse-graining in granular simulations. I have found the paper "Three-dimensional discrete element models for the granular statics and dynamics of powders in cavity filling - C. Bierwisch Ã, T. Kraft, H. Riedel, M. Moseler (2009)" where the dimensional analysis is explained.

My question is: do I have to adjust the material properties used by the gran model hertz (Youngs modulus, Poisson ratio, coeff of restitution, coeff of friction) if I scale the particles by a certain factor?