LIGGGHTS® - User Forum

Hi, all

Is it possible (or simply naive) to run the MD and DEM simultaneously in one model? I am wondering if it is feasible to use a cluster of atoms to assemble a nano granular particle which can contact with other particles? The interaction between the atoms within one particle is governed by MD potential function (e.g. Lennard Jones) while the contact between particles follows the contact law (e.g. Hertz).

Any suggestion and discussion is appreciated.

cheers

Yang

Hi!
Has anybody got LIGGGHTS working under Sun Grid Engine with $round_robin -scheme? I've only managed to get it work with $fill_up and even then every calculating node for the simulation has been on the same computer. I'm using OpenMPI-1.5.3 and it has been compiled --with-sge (haven't seen any difference, if this flag has been used or not...). Without SGE it works perfectly fine. Some simple hostname calling scripts under SGE with mpirun works also fine.

- Timo

Hi, all

How to choose an appropriate timestep in LIGGGHTS? In the examples, I presume the timestep, e.g. 0.00001, is not generally applicable.

Normally a ratio of the out-of-balance force over the average contact force is used to assess if the granular system is stable or not. I'm just wondering whether this is robust in LIGGGHTS or I have to take care of the timestep by myself in each simulation?

cheers

Hi all,

I have been scratching my head over this one today - my simulation works fine unless I try to dump the per-particle forces with compute pair/gran/local - then it runs for a while, but crashes with:

2374000 1123 6.1525987
[comp-l06:09946] *** Process received signal ***
[comp-l06:09946] Signal: Segmentation fault (11)
[comp-l06:09946] Signal code: Address not mapped (1)
[comp-l06:09946] Failing at address: (nil)
[comp-l06:09946] [ 0] /lib/libpthread.so.0(+0xf8f0) [0x7f19103438f0]

Hi all,

I minor but potentially useful feature request here - would it be possible to add a simple binary flag to the compute pair/gran/local that shows if an interaction is periodic? For contact force chain and similar visualisation this would make it easier to avoid connecting points at opposite sides of a simulation domain etc.

Regards, Mark

Hi Christoph,
I found that LIGGGHTS can not dump stresses on the CAD cylindrical wall properly when the ratio of the diameter of beads to the diameter of cylinder is bigger than 0.02; however, below this ratio, the stress profile is good. But, using this low ratio is computationally expensive. Is there another way to do so?

Thanks,
Ram

Hi,
Is there a way in LIGGGHTS to make granular chain? For example, to glue some granular particles together to make a chain.
Thanks,
Ram

Hi, I tred to install liggghts for the first time. (new to Linux as well).

After typing 'make fedora' in /src got a whole bunches of can't find files. I looked into the src directory, and they are all there.

make[1]: *** [memory.d]Error 1

memory.cpp:14:17: fatal error: mpi.h: No such file or directory
compilation terminated.then it leaves the directory
make[1] Leaving director ' /home/.../liggghts_1p4p3/src/Obj_fedora'
make: ***[fedors] Error 2.

Not sure how to proceed from here. Any help is appreciated

Hi

I am trying to develop a new version of fix_pour by combining the "regionExempts" function of pour/dev with pour. I have created a new pour called pour/exempt and copied accross all the relavent bits of code. I have also made the necessary links to these other files as well: mech_param_gran.cpp, region_block.h (and cylinder), fix_gravity.h, pair_gran.cpp and style_fix.cpp.

Hi all,

I am using compute pair/gran/local and the corresponding dump to look at the particle-particle contact data (and heat flow), but also need to look at particle-wall interactions. As far as I can see, these are not included in these computes/dumps?

I think this would be a very useful addition - I guess it would require assigning each wall an ID etc. In particular I need to identify particles in contact with the wall, and sum their heat fluxes etc.