LIGGGHTS® - User Forum

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

jumping of particles in a rotating drum

Submitted by ZYan on Tue, 02/03/2015 - 11:37

Dear users,
currently i am working on a rotating drum mixing project. I found something is strange to me (please refer to the attached fig.). Sometimes the particles are jumping and flying. i had same issue in other mixer (the reason was due to the mesh). i have tried again playing with finer mesh. still have the same probelm. What do you think might be the reseaon? here is the parameter i am using:

Mesh error: dimensions too small

Submitted by joshiga on Thu, 01/29/2015 - 13:05

Hi,

I'm new to LIGGGHTS and need your help in setting up a run.
I'm getting following error,

ERROR: Mesh error: dimensions too small - use different unit system (multi_node_mesh_parallel_I.h:535)

I searched the LIGGGHTS forum and got a suggestion to change the STL file format to ASCII.
I changed the STL file format to ASCII, still the error persists.

Do you have any other suggestion to fix this error?

Best Regards,
Girish

Book-keeping of Wall charge

Submitted by clarence91 on Thu, 01/29/2015 - 00:34

Hello everybody,
I am a new bee to LIGGGHTS.
How can I have a book-keeping of the wall-properties of my domain? I just have to introduce a variable and I am not pretty sure about how to define it.
All I am doing is calculating the charge transfer from particle-particle and particle-wall contacts.
I am able to save the data about particle charge (q[i]=q[i]+dq) (q-charge) at each time-step.

Compressive Force on a Granular Soil

Submitted by nadji on Mon, 01/26/2015 - 17:10

Hi to all
I would like to use DEM to simulate the pushing of a granular soil due to a compressive
force from one of it's sides.
This subject is Geotechnics is called the stick-slip phenomenon. We have done the experiments on a box
filled with beads to simulate the granular soil. The box is open from the top but one of it's sides is a moving
wall that can be pushed towards the granular medium with a constant compressive force. Progressively in time
a line somewhere in the middle will develop to show where the soil will break.

Capillary force - hysteresis

giuraso's picture
Submitted by giuraso on Mon, 01/26/2015 - 16:01

Hi all,

I need to implement a DEM simulation involving capillary force between particles. I use a hooke/stiffness contact model.

The capillary force model is the Willett model:

Willett, C. D., Adams, M. J., Johnson, S. A., & Seville, J. P. K. (2000). Capillary bridges between two spherical bodies. Langmuir, 16 (24), 9396–9405.

The capillary force is given by a liquid bridge that is created when two particles come into contact and persist until a rupture distance is reached.

The first step (of a long path) is:

Volume_Limit of fix/particletemplate

Submitted by NTT1508 on Tue, 01/20/2015 - 12:35

Hi all,

The manual describes about volume_limit of fix/particletemplate/sphere that LIGGGHTS will throw an error if the particle volume too small compared to machine precision. My question is how to adjust machine precision with default limit 1e-12 of LIGGGHTS. For examples, I'm playing with particle's size D=50micron that has volume of 5.4e-14 m3. It's obviously lower than default value. Does it cause serious error to simulation result?

local data

Submitted by chris.ab on Mon, 01/19/2015 - 19:03

Dear All,

In my simulation ,I am trying to print out all data from the command .. wall/gran/local .. to be in one txt file but I could not.

In Pre-atom or global data, It can be defined in (variable equal command) and then use (fix print command) to store all the data.

I am looking to print (local data) in one txt file (like print do). Is there any way to do that?

thank you in advance for your help.

Regards.
Chris

contact/atom

Submitted by abdulrahmanalharbi on Mon, 01/19/2015 - 17:02

Hi all,

I am trying to calculate the total number of contacts.
In my simulation, I used( compute contact/atom command) to calculate the number of contacts. Then, I used (fix print command )to store all the data in order to sum all the numbers and get the total number of contacts.

variable C1 equal c_NOC
fix cont all print 10 "${C1}" file contact.txt screen no
compute NOC gr contact/atom

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