LIGGGHTS® - User Forum

Hi,
Imagine a 3D particulate channel flow with periodic boundaries along the depth. So the "2D" parabolic velocity profile can be imposed at inlet of channel. The particles are continously inserted at a small region near the inlet.
How can I impose the parabolic profile on the particles? Because with the fix insert commands i can only impose a uniform velocity to all particles. Can I do this by just some additions to the input script, or do I really need to modify the fix insert (say insert/rate/region) code? I would really appreciate any suggestions.

Hi,

I am solving a system which is highly static and only has very low velocity fluctuations. So I end up with very low velocities and with the default precision the simulation ends up at zero kinetic energy and shows NaN as kinetic energy. How is it possible to increase the precision of the solver?

Thanks
Mohammad

Hi friends,
every time when i run script, i got following error;
Reading STL file 'meshes/impe.stl'
Setting up run ...
ERROR: Mesh (id cad2): Mesh elements have been lost / left the domain. Please use 'boundary m m m' or scale/translate/rotate the mesh or change its dynamics (/build/liggghts-QCz4in/liggghts-3.3.1+repack1/src/multi_node_mesh_parallel_I.h:567)

Please help me to resolve this error,

Thanks

How can I extract information on the contact model properties in my simulation (e.g., Young's modulus, coefficient of friction, etc.)? For debugging purposes, I want to be able to check that the right contact properties are being applied to different groups of particles and that the coefficient of friction changes when I put in a new 'fix property/global' partway through the simulation. I already know how to extract forces, overlaps, etc. using compute pair/gran/local but this doesn't give me any information on the actual contact model parameters.

Hello,
I am simulating the filling of a box with a large number of particles (10^5 to 10^6): first I insert the particles in a bigger volume and then I let them pack under the action of gravity.

Which is the best choice of processors to parallelize it? I would like that the Z axis is divided into non-constant grid sizes... e.g., so that more processors compute the particles at the bottom of the box and only 1-2 at the top (when the particles will stay for only a short time before packing).

Do you have any suggestion?
Thanks a lot,

rob1

Hallo,

I have a question concerning superquadric particles:

http://link.springer.com/article/10.1007/s40571-016-0131-6

Will this code be published in the public version?

Best wishes

Johannes

Hi everyone

I've got a problem by using the command massflow/mesh.

I want to simulate a micro-sandglass and would like to count the particelflow that passes the MassFlow.stl mesh (see Example_1).

I also made a simple simulation with only four particles (Example_2) trying to get more knowledge about this mysterious file called massflow.dat, whitch is written in this line:

Hello,
I am trying to increment a user variable every thermo output.
Some background, I am trying to get a soil bed to a certain void ratio. I am doing this by stepping 5000 and then checking what my void ratio is. If it is my tolerance, I continue the simulation. If not, I step another 5000 and check again.
What I would like to have though is a continuous simulation time in my thermo output. I was doing this using

variable sim_time equal dt*elapsed

but every time I would reuse the "run 5000" command, elapsed. I then tried the following

Hi,
I am trying to run a triaxial test on a cube shaped sample. I currently inset stl files (3 files for the 3 faces) using the fix_mesh_surface_stress_servo command and another 3 stl files using the fix_mesh_surface_stress command. Once I have finished the consolidation stage of the test, I want to change the top mesh (currently servo controlled) to a non-servo wall so that I can apply a constant velocity to it. Is there a way of doing this?
Many thanks,
Rector

Hi,

I am wondering how could I get the previous version (3.5.0)? I ran a simulation with 3.6.0 using a restart file generated from 3.5.0 but get different results. Anything I could after git pull the repository?

Many thanks