LIGGGHTS® - User Forum

Hi guys,

I have a question.

I am running simulations that needs to be constrained in the z axis and periodic in x and y.
Since I am working with high volume fractions (higher than 0.7), I use the particletemplate/sphere command with an initially low volume fraction, then I compress the box to higher it.
This compression has to preferrably be isotropic (https://www.comsol.nl/model/isotropic-compression-with-cam-clay-material... - for more info).

Hi all,

I am getting following error while using wall/reflect function.

ERROR: Invalid fix style: "wall/reflect" (modify.cpp:820)

The command written is

fix walls all wall/reflect xlo EDGE ylo EDGE zlo EDGE xhi EDGE yhi EDGE zhi EDGE units box

I am using liggghts 3.3.0 version.

NOTE: The idea behind using wall/reflect is to avoid particles crossing wall. The wall is already defined as granular wall using fix/gran.

Appreciate your help in resolving this.

Thanks
Tuks.

Greetings,

I'm writing because i can't understand how to use the point_at_outlet keyword. Specifically, i don't know how it works. What i understand is that you define a point in the "outside" part of the mesh, but what simbolize that point?. For example, my cylinder-shaped mesh is in the coordinates 4.48,0,0. I would have to set the point in 4.9,0,0 in order to the keyword works?

Another thing, the inside_out keyword, how it works too?

I hope that someone can answer my doubts.

Nicolás.

Hi

## version 3.3.0

I am running this code, which inserts two layers made of two sets of random generated packings.
Since I need to compress the volume in order to reach a relatively high volume fraction (higher than 0.8), I apply an isotropic compression to the box, reducing its final dimension.

The problem I have is that the potential energy of the system during compression and relax, is always zero, while the kinetic energy has quite reasonable values.

I am simulating particles rotated by an impeller in a cylindrical container (see sample image attached here). The impeller has two blades (180 degree apart) and is rotating at defined speed.

The LIGGGHTS 3.3.0 release announcement states: "Also made an important improvement to region mesh/tet. The all_in yes feature was implemented, and some algorithms necessary for particle insertions have been improved considerably. You should see a speed-up when using tet meshes for insertion."

Is this feature fully implemented ? All_in seems to be only an option for "fix insert".

Inspecting the code reveals that a mesh/tet region always enforces the caluclation of the corresponding surface of the region

Hello,

I would like to compute the total force acting on only some portion of a stl mesh.
I know that dump mesh/vtk output the stress components.

What I am looking for is to obtain an output like
fix ... ave/time ... f_cad[1] f_cad[2] f_cad[3] file.dat
but not on the whole cad, only in some parts of it.

Maybe should I split the cad file in different parts and import different stl files?

Thanks,
rob1

Hi,

For nano-particle simulations (particle-wall and particle-particle collision), can I use granular model? or do I need to go with something else?
(wall/gran and pair/gran)

Any suggestions?

Thank you.

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.