LIGGGHTS® - User Forum

Dear colleagues,

Recently I am repeating a same simulation with different cores (1-128 cores ) with our HPC.

I find two things that are strange to me:

1. When the number of the cores changes, the number of the particles that are created from the input script is different, the difference is not big (a few to ten particles).

Is this a bug of the liggghts or i set wrong parameters?

I imported my stl geometry (created using solidworks) into Paraview. I found the Origin of this stl geometry was not the same as bofore being imported. Did someone come across this problem? My antoher question is how the coordinates of the CAD geometry is read in the Paraview?
Thank you,

ZYan

I want to simulate a particle inlet boundary with given solid volume fraction and velocity, i.e the solid volume fraction and velocity in this boudary region is always fixed. I defined a region above the boundary, calculated the massrate, and used the insert/rate/region command. Since I want to keep the solid volume fraction fixed, should I set the insert_every to be 1?
I found many warnings come out.

Hi everyone,

I need to make a fluid-particle simulation but I can't use CFD for the fluid because of the length scale of my particles interactions. According to this, i'm looking to make a mesoscale coupling between SPH and DEM. I know that LIGGGHTS has both models but is it possible to couple them?

Thanks in advance.

Dear all,

i'm simulating granular particles flowing through a pipe. Does LIGGGHTS provide a method to count particle-particle collisions per timestep?

Best Regards
Felix

I am just wondering that is there any way to automatically adjust the timestep in the simulation based on the size of newly generated/inserted particles. One such way is to use fix dt/reset but in that the impornat keyword is XMAX which seems difficult to produce.

Hi,

when I am trying to use the compute inertia/molecule on a molecule defined by fix rigid, I receive an error message like:
"ERROR: Invalid compute style (modify.cpp:883)"

I compiled LIGGGHTS together with the MOLECULE package and I am wondering why this would be an invalid compute style?

My files are attached to this post.

Best regards,
MiRa

Hi Colleagues,
I have problems with the .stl geometry rencently. I used SolidWorks to create
3D geometric models and then save them in .stl format as the mesh walls. However,
when I viewed the geometry with Paraview, they looked like solid. I noitced in the tutorial examples, all the geomery are surface mesh (please see the attached figures). the example.png is from the tutorial example, and the myexample.png shows my own example.

I failed to save plane/surface in the solidwork as .stl.

Hello,

I'm thinking about how to choose the optimal time increment for my simulations. I set up a very simple testcase in order to study the behaviour of contact interaction between particles and STL-geometries, defined as wall.
Video: http://www.youtube.com/watch?v=IBf3vUwHh-w
First, I calculated the timestep as provided by many posts in this forum with the formula dt = 0.2*dt_rayleigh:
r = 0.005
rho = 8000
Y = 5e6
nu = 0.3
G = Y/(2*(1+nu)) = 1923076.92

Hello,