LIGGGHTS® - User Forum

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.

Greetings,

Is there a way to LIGGGHTS could register the real time of a full simulation?

Thanks,

Nicolás.

Hello,
I am a new user of LIGGGHTS and I am simulating a shear cell with:
- upper surface as servo, to apply a force in y direction
- lower surface moving in x direction
- fixed walls in the z direction
- boundary p f f
All the surfaces are imported as STL files.

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: