LIGGGHTS® - User Forum

I feel dumb but when logged in it says go to bottom of page for download - missing!!!!!

JB Perth Australia

Hi everyone,

when using gran model hooke/stiffness, I noticed that the gamman and gammat specified are weird for the case of absolute_damping = 'off'.
In another dem code PFC, the parameter specified for viscous damping is damping ratio, however liggghts gives the expression:
gamma(n)=m(eff)*gamma(n,specified)
I wonder if this gamma(n,specified) has a specific meaning that I ignore.

In PFC ,the expression is:
gamma(n)=2sqrt[m(eff)*kn]*gamma(n,specified)
and the gamma(n,specified) is called damping ratio in the normal direction.

thank you.

I am trying to use store_force_contact in wall/gran and I am using a mesh as the wall. Here is the line I am using:
fix granwalls all wall/gran model hertz tangential history meah n_mesh 2 meashes mesh1 mesh2 store_force_contact yes

But when I add the above keyword store_force_contact yes, then I get the following error:

Error: Invalid fix style: "contactproperty/atom/wall" (../modify.cpp:820)

I also want to output the above force value as well in dump please help me resolve these issues.

Thank you.

Hello,

I have a simulation of a process of sedimentation. Initially the particles are distributed over the whole simulation box but over time they concentrate in one end. To speed up the simulation I have two ideas/questions concerning the effective usage of processor power:

I am trying to run this script file but it is showing that velocity projection on face normal is less than 1e-3.

Script File

#Simple chute wear test

atom_style granular
atom_modify map array
boundary f f f
newton off

communicate single vel yes

units si

region reg block 0. 0.3 -0.05 0.05 0.0 0.2 units box # 30cm x 10cm x 20cm
create_box 1 reg

neighbor 0.003 bin
neigh_modify delay 0

#Material properties required for new pair styles

I am new user of LIGGGHTS and I have to study the granular flow on inclined plane with walls .

1. For that should i design the mesh which is already at desired angel or it can be simple plane with walls and gravity with component in x y and z direction.
2. How to design the inclined plane and and used mesh/gran command
3. how to see the simulation animation with LIGGGHTS.

Please any one clarify my doubts.

Regards
pnkumar

Hi All,

In some book and articles it's mentioned that coefficient of restitution isn't a constant parameter and it depends on impact velocity. I think it isn't implemented in liggghts and it may affect simulation results, so how we should consider this problem?

Thanks in Advance,
Reza

I find that the compute property/atom command dose not work with multisphere, it cant give the force on each atom(fx fy fz). It always be 0 0 0. I guess there should be a restriction along with the compute property/atom command. And I wonder how to get the resultant force on each multisphere body on each time-step.

Hi all.

I've downloaded the Voro++ package and installed it, but I still get the following error while using compute voronoi/atom:

ERROR: Invalid compute style (../modify.cpp:982)

I've followed the steps mentioned in the documentation while installing it, but I'm not sure what the following steps mean: