LIGGGHTS® - User Forum

Hello
I am using LIGGGHTS-flexible fibres.
I my simulations I need to group certain atoms based on a spatially non uniform function. Since difficult to implement in LIGGGHTS directly, I plan to extract the atom IDs using a Python/Matlab script, then define grouping of those specific atoms. I have following two questions in this regard:
1) Is it possible to use group command such that I can group specific atoms read from a text file ?
2) What is the template to store atom IDs in such a text file ?

Any suggestions will be highly appreciated

Hi there,
I am trying to implement a drag force on particles flowing through a hopper with a upper cylindrical section and lower conical section. The drag force is to be calculated based on "void fraction" around each particle, then scaling of superficial velocity of the gas by the void fraction, and then getting value of Reynolds number, coefficient of drag, inputing into formula for drag. Snippet of the code is given below. I am facing some issues.

Hello, there is a way as shown in the examples to grow spherical particles in a packing...can the same be done for superquadric particles?

Hello is there a way to make all the particles inertialess? Can someone please help with the same?

Hello, although tbe vtk superquadric visualizer is available , it shows the soft ellipsoids as interpenetrated, while maintaining their shape. Is there away to visualize the deformed the ellipsoid at the point of contact?

Hi.

Hello,
I am facing one grave problem. The values of coordination number and energy values per atom is not correct. It is showing very very less values.
Kindly see the code once and help me with this problem as early as possible.

atom_style granular
atom_modify map array
boundary f f f
newton off

communicate single vel yes
processors * * *

units si

region reg block -0.01 0.35 -0.01 0.1 -0.01 0.15 units box
create_box 2 reg

I'm writing the command: write_dump all mesh/vtk meshfile*.vtk stress vel stresscomponents area

This command worked in previous versions when it was mesh/gran/VTK and I've corrected it to mesh/vtk, but I'm still getting errors with this command that are indicating the keywords are wrong. What is the correct way to do this in version 3.8?

Hello Mschramm,

As we discussed in the previous forum about particles repeated id, I found that particles id are repeated in my SIlo silulation.

I still didn't check the LIGGGHTS examples.

I converted all dump files in a csv file by using python. I tried to plot particles after 400000 or 500000 steps(rowsin csv) which is almost at the end of simulation. I was expecting all the particles will be on the floor but I found that some of the particles are still hanging on the top of the silo.

Is it because I didn't use delete atoms comand?

Hello,
Please find my code below. I am simulating a problem in which particles are allowed to enter in a column and then of the column's gate is removed to create a flow. I am losing atoms after certain trials of insertions. This is reflected in the post processing (Paraview) as particles vanish from the column during insertion.
#Simple granular column collapse

atom_style granular
atom_modify map array
boundary f f f
newton off

communicate single vel yes
processors * * *

units si