LIGGGHTS® - User Forum

LIGGGHTS® related topics can be discussed here: discussion about models, installation, feature requests and general discussion

LIGGGHTS generating "Complex" eigenvalues for superquadric orientation tensor

Submitted by coshivam on Fri, 03/16/2018 - 15:06

I am trying to simulate ellipsoidal particles using superquadrics atom_style. Therefore, I started testing with the input file that was released by LIGGGHTS in the example folder (It is attached). For visualization in Paraview, I have compiled it with the Tensorglyph plugins.
I have also attached the video of visualization. I am not able to understand, why after the collision the semi-axes values of both the ellipsoids are changing. For getting a closer look at the problem, I calculated the eigenvalues of both the ellipsoids and found that they are

multisphere break problem

Tarun De's picture
Submitted by Tarun De on Tue, 03/13/2018 - 14:31

Dear liggghts users,
I want to break multisphere through liggghts. I want to break multispheres when the z coordinate of the multsphere exceeds certain height(here .4 m).
i considered gravity in the +ve z coordinate.
here is my input code.
#Multisphere

atom_style sphere
atom_modify map array sort 0 0
boundary m m m
newton off

communicate single vel yes

#PUBLIC version only supports serial execution
processors * * *

units si

region reg block -0.3 0.3 -0.3 0.3 0.0 0.5 units box
create_box 1 reg

break particle

Tarun De's picture
Submitted by Tarun De on Sun, 03/11/2018 - 12:53

hello everyone,
I wish to simulate one system where particle(sphere or multi-sphere) breaks when it attains some certain height. can anyone please help me with some suggestion? I was going through multisphere/break, but could not figure out threshold value.
any suggestion will be highly appreciated.
thanks in advance.

set an end stop for servo wall

Submitted by t9000 on Fri, 03/09/2018 - 13:48

Dear all,

I want to use the servo wall (cap) to close a pipe. The granular material in the pipe will built up a pressure on the servowall so that the cap open at an predefined force value. So i need the servo wall to stop at the ending of the pipe.
I specify the servo command as followed:

fix cap all mesh/surface/stress/servo file meshes/cap.stl type 2 com 0. 0. 0. ctrlPV force axis -1. 0. 0. target_val 1 vel_max 0.1 kp 5.

is there a command to stop the wall at a specified coordinate in moving direction of the cap?

Best Regards

Triaxial test using LIGGGHTS-WITH-BONDS

Submitted by amanso3 on Fri, 03/09/2018 - 02:55

Hello,
I am trying to do a triaxial test using LIGGGHTS-WITH-BONDS. I have never really used this software before and I am struggling in understanding what the parameters mean. The particles are in a box were one wall is applying pressure through the mesh/command/stress/servo code. I am trying to calculate the stress the particles are causing on the other walls and my input parameters are as follows:
Minimum ball size -2.5e-4 m
Maximum ball size -4.5e-4 m
Density -2650 kg/m3
Ball and bond elastic modulus - 40 e9 Pa

particles not passing through sieve

Submitted by jyothish on Thu, 03/08/2018 - 14:07

Hello everyone

I have created a sieve through which particle can pass through (sieve size 75 micrometre) .But when I run the simulation in LIGGGHTS the particles (particle size 50-100 micrometre) does not pass through the sieve instead they settle on top of sieve. Can anyone suggest any method to sole the problem.

Thanks in advance
Jyothish

Particles sticky on the auger and not flowing

Submitted by bilalelkassem on Wed, 03/07/2018 - 18:33

Hello,

I want to simulate powder auger dosing of particles with size around 600-800 µm.
The problem is that the particles are sticking to the auger and not flowing down. I changed a lot the parameters of the friction, cohesion and rolling friction and still didn't work. What could be the problem?

Attached are some screen-shots of the input script and the problem occuring.

Could you please suggest some tips for a solution?

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