LIGGGHTS® - User Forum

LIGGGHTS® related topics can be discussed here: discussion about models, installation, feature requests and general discussion

liggghts-with-bonds bond creation

Submitted by liggghtschr on Tue, 05/30/2017 - 12:40

Dear liggghts users,

I want to set up a simulation with bonds (I am using liggghts-with-bonds) that has atoms with different sizes. I was not able to get different atoms with the „create_atoms“ command.

My idea was to first insert the atoms with the fix insert/pack command, let them settle and then create the bonds in order to have bonds and different sized atoms.

Force on mesh/surface

Submitted by Weijing on Wed, 05/24/2017 - 10:26

Hi there

Is it possible to calculate the force acting on the mesh/surface?

In my simulation, I use the fix top all mesh/surface/stress/servo file bottom.stl type 1 scale 0.03 move -0.015 -0.015 0.1 com 0. 0. 0. ctrlPV force axis 0. 0. -1. target_val 0.0003467 vel_max 5e3 mode auto ratio 0.01 to cap the particles. how can I manage to know the force on the mesh? because I suppose this command will set the wall compress the particles by 0.0003467N.

Thanks
Weijing

stickness of multisphere particles to impeller rod?

Submitted by kashif saeed on Sun, 05/21/2017 - 18:38

Hi,
i m working on mult-isphere particles mixing in cylinder . problem with my simulation is that some of the particles remain suspended during insertion and stick with impeller rod. if there is anyone who can help me out. i m uploading a picture of my problem. please help me.

thanx

2D Couette flow

Submitted by en9apr on Thu, 05/18/2017 - 19:42

Hello,

I am new to LIGGGHTS, so I tried to modify a tutorial example for a granular flow to create a 2D Couette flow. This is the example I am modifying:

https://www.cfdem.com/media/DEM/docu/Section_input_script.html#an-exampl...

I have got so far with the modifications, but I hit a problem. When I try and convert the dimension to 2D using this line:

dimension 2

The error message appears:

investigating different rolling friction models

Submitted by msandli on Wed, 05/17/2017 - 17:57

I'm trying to investigate how the different rolling friction models in LIGGGHTS effect my simulations. My initial simulation used the cdt model for the particles and walls, and I wrote restart files to prevent me from having to run multiple simulations from the very beginning.

However, when I change the rolling_friction model on the wall/gran fixes, I get an error:

ERROR: Fix contacthistory/mesh (id tracker_mesh1): saved simulation state used different contact history model - can not restart (../fix_contact_history.cpp:528)

Coupling OpenFOAM and LIGGGHTS

Submitted by en9apr on Wed, 05/17/2017 - 12:05

Hi,

I wondered if there exists a way of coupling a solid model created in OpenFOAM, which solves the wave equation to a DEM model created in LIGGGHTS? The physical situation is a pipe filled with powder and the solid pipe is vibrated to fluidize the powder. The particle phase is dry (no effect of interstitial fluid) but the powder is affected by the vibrations of the solid model through the motion of the boundary, which changes throughout the solid part and depends on the frequency of vibration.

Kind regards,

Andrew

new torque flag in rolling friction models

Submitted by msandli on Mon, 05/15/2017 - 23:08

I see the new release has an additional flag that applies to the rolling friction models, the "torsionTorque" flag. I'm having trouble trying to visualize what the "normal torsion" actually is. Could you provide a more in-depth explanation (pictures are helpful!) or provide an article that explains it?

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