LIGGGHTS® - User Forum

Hello,

I am a beginner of LIGGGHTS. I am troubled by the meaning and effect of the keyword com in servo command
eg:
fix x0 all mesh/surface/stress/servo file meshes/x_0.stl type 1 scale 1 com 0.5 0.5 0.5 ctrlPV force axis 1.0 0.0 0.0 target_val 5e4 vel_max 1

In the document, the com was described as the center of mass. I do not understand what it does. I try to change its value, but it seems to get
the same result.

Can anyone help me?

Thank you!

Wang Xiukai

Hey everyone,
I am a third year undergrad in Aerospace engineering.

Hello Liggghts Users,

i want to move my mesh between two points at a given frequency along the x-axis. I´m using the linear/variable command for this since i also have to add rotation around the x- and y- Axis later down the line at the same frequency. I used the wiggle command before instead of linear/variable but that has led to an unwanted overshoot.

My Problem now is the correct use of the linear/variable command.

The Error is:
ERROR: Invalid syntax in variable formula

I use the following command line:

Hello!! I am very new to LIGGGHTS. I am trying to model the particle settling on a solid bed for the simulation of Laser Powder Bed Fusion(LPBF). Is anyone working on the same topic or has done the same in the past? It would be really helpful as I am running out of time.

Hello LIGGGHTS forum,
really appreciate your help.

I want to save the distance between particle insertion surface and mesh surface in dump file.

How can I save this distance/height ?

Thank you.

Hi everyone,
I am trying to simulate the angle of repose test by lifting cylinder test, according to the paper by Thomas Roessler, "Scalability of angle of repose tests for the calibration of DEM parameter"
I have two questions:
1) When I tried to move my cylinder up to let the particles flow out, my particles do not flow out. The particles seem to be stuck with the cylinder . Does anyone know how to fix this?

Hi Everyone

I am trying to import particle configuration by using [read_data] command. But I am getting the following error.

I have been trying to model repeated load triaxial test. It's a stress-controlled test. I was able to match the loading curve but during unloading force is suddenly dropping to lowest levels. I experimented with different kp values for top servo wall and defining several unloading target levels but I did not get desirable result.
I am attaching some of the pictures for reference. Please let me know if I can do something to achieve the proper result.

Hello everyone, I'm using the latest version of LIGGGHTS and atom style superquadric on a university cluster. I want to do parallel computing of superquadric but it seems like that there is no difference in computational time for using 4 or 8 or 12 cores of CPU at all.

I wanted to ask if there is some rule for distributing CPUs for a simulation or some kind of lack of mpi library for parallel computing of superquadric atom_style?
I appreciate any helpand tips regarding this issue.
Thanks in advance, Hamed

Hello LIGGGHTS users:
I want to count the number of the particles contact with a specified wall every time step, is there any commend can be used to implement this???
Thank you!
Zhang Peiyun