LIGGGHTS® - User Forum

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

Increase the coefficient of restitution will sharply increase real time spent for a 2D simulation

Submitted by Wu Wencong on Wed, 01/15/2020 - 15:56

Dear all,

I use LIGGGHTS-PUBLIC 3.8.0 to perform 2D simulations for particle mixing in a rotary drum.

When I use the real coefficient of restitution (0.82) for the mixing material, the real time spent is much higher than I use the default value 0.5 in many other simulation cases.

Use Fix_evaporate command to delete particles in the Latest CFDEM version Errors!

Submitted by Donald Trump on Wed, 01/15/2020 - 03:38

I recently met this problem when I compiled a pack of source codes, does anyone have any clues what this syntax error is? The application file is called fix evaporate.C in the directory. I want to use this command to calculate the outflow mass rate and delete some particles at a certain rate in my simulation! I added this file into the original SRC directory and recompiled, then the system showed me the information below:

superquadratic dump error

Submitted by nabdoulm on Mon, 01/13/2020 - 16:59

I am attempting to modify the auger tutorial script to use superquadratic particles and I am running into the following error: Invalid attribute in dump custom command (../dump_custom.cpp:146). I believe the error is related to the dump syntax. Any help and suggestion is greatly appreciated. I have attached the input file and the relevant geometry folder.

Reduce the porosity of particle bed

Submitted by Michelle Phan on Mon, 01/13/2020 - 06:24

Hello everyone;
I am trying to validate my numerical model with previous model. Therefore, I am trying to generate 6614 particles into the region 0.028 x 0.0054 x 0.0576, which the particle bed porosity is 0.39. However, I cannot obtain the same result.
LIGGGHTS inserted less particles than requested and my porosity is much higher than model in previous study

pair/gran/local - error while using the "contactPoint"

Submitted by Khan on Fri, 01/10/2020 - 05:48

Hi Everyone!

When i use the "compute pair/gran/local" using the following:

compute cpgl all pair/gran/local pos id force contactArea
dump dmp_cpgl all local 1000000 output/fc/cpgl*.dump c_cpgl[1] c_cpgl[2] c_cpgl[3] c_cpgl[4] c_cpgl[5] c_cpgl[6] c_cpgl[7] c_cpgl[8] c_cpgl[9] c_cpgl[10] c_cpgl[11] c_cpgl[12] c_cpgl[13]

The above works perfect for me!

However, if i would like to know the coordinates of the contact point at which the force is calculated, i need to use the following:

Post processing / Rendering multisphere particles

Submitted by Michelle Phan on Fri, 01/10/2020 - 00:12

Hello everyboday;
I am working on irregular particles. I clumped the particles together by the fix multisphere command. I use Paraview to visualize the irregular particles but the rendering image is not good. It is hard to see the shape of particles. I am wondering if there are plugin of Paraview or other programs that can help me to visualize the shape better?
Thank you

Skip particles during computation

Submitted by amgroen on Thu, 01/09/2020 - 17:38

Is there a way to have a group of particles being skipped by collision detection and locked in place, ideally while reducing the computation time.

A simulation that I'm running involves filling a tall cylinder with particles and I want to ignore the majority of them and only freeze a certain distance from the top for the next layers.

Simulating the entire stack is not feasible computation time wise on my desktop.

I haven't been able to find functionality like this in the documentation

Thanks,
Alex

Changing the environment

Submitted by PRATBHARAT94 on Mon, 01/06/2020 - 21:34

Hello,
I am very new in the field of LIGGGHTS. I have already installed LIGGGHTS 3.7.0 version. But I have to work with atom type superquadrics , I have installed the version 3.8.0 too. But while I am simulating the case. It was creating the 3.8.0 version environment. Please tell me how can I change the environment??
Thanks in advance

Mass_Temperature for fix mesh/surface

Submitted by amanr on Mon, 01/06/2020 - 12:45

Hi,
I am trying to simulate a cold hollow sphere mesh surrounded by hot particles. I am using the mass_temperature tag for this, but when I dump the mesh temperature, it doesn't change with time even though the surrounding particles are at a higher temperature than the mesh. Does anyone have any idea if this feature works in LIGGGHTS?

syntax used:

fix cad2 all mesh/surface file Indium226mm.stl type 2 move 0 0 0.007 temperature 300 mass_temperature 0.35

dump meshtemp all mesh/vtk 500 temp*.vtk temp cad2

Thanks!

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