LIGGGHTS® - User Forum

Hi all,

I need to change a parameter for my walls. E.g. I want to change the damping flag (or the velocity amplitude if I am doing wiggle with a LAMMPS-style plane wall).

My impression is that I need to use the command fix_modify in my input script. But then I need to add the function modify_param in my wall class, which will take as inputs the arguments of fix_modify and reset the values I require.

Does this sound fine, or am I missing an easier way of doing this?

Thanks,

George

Hi all,
How can I use LJ units for density and yougsModulus?
Thanks in advance,
Ram

Hi Christoph,

I would want to write a new dump class (dump_gran) which saves the connectivity and the scalars as: normal force, damage parameter, radius. Thus, it will be possible to display with paraview the lattice beams or the chain force for granular simulations. But I need help to understand the class Dump_mesh and know where the functions are called:

Hey Everyone,

I'm trying to build LIGGGHTS in Cygwin (and before anyone suggests otherwise - Yes, I need to do it in Cygwin, and other platforms won't work for what I require). I've edited the makefile.cygwin and the .bashrc files and have overcome most of the problems associated with building the executable. However, after "make cygwin" runs for a while, I get the following errors and the build does not complete:

#C:\MSDEV\LIB -o ../lmp_cygwin
#c++: C:MSDEVLIB: No such file or directory
#make[1]: *** [../lmp_cygwin] Error 1

Hi,

I want move the side walls as a function of time t to conduct the undrained triaxial test with no volumetric change. However, when I try this fix move variable command, it seems to be some errors in my script:

variable dy equal 0.01/(0.1+${vc}*dt*(step-40000))-0.1
variable vy equal 0.01*${vc}/(0.1-${vc}*dt*(step-40000))^2
fix F_moveleft all move/mesh/gran variable NULL -0.05-0.5*${dy} NULL NULL -0.5*${vy} NULL units box leftwall 1

The output of liggghts:

variable vc equal -0.1
variable dy equal 0.01/(0.1+${vc}*dt*(step-40000))-0.1

Hi,
Does granular pair style output force info to compute pair/local? As LAMMPS doesn't have such capability.
Thanks,
Ram

Hi Christoph,
We can assign the properties of mesh wall/sphere from atom_type value. Can we assign density of that mesh wall/sphere like this way?
....
create_box 2 reg
group sphere type 2
set group sphere density 2500
...
..
fix cad all mesh/gran/stressanalysis stl/sphere.stl 2 0.1 0 0 0 0. 0. 0.
...
...
Will it change the density of sphere.stl?
Thanks
Ram

Hi Christoph,
Can I run two different simulations at same time on same system? Will there be any effect on the outputs of the simulations?
Thanks,
Ram

Hi Christoph,

In the class atom, the sphere positions are sorted, it exists the array j = tag[i] to indicate at the line i you will have the sphere number j. I did not find, if it exists an array such as : i = invtag[j].

This array invtag[] is important in my case, because I load the interactions pair (Si, Sj) and I have noticed that the values of x[Si] do not correspond to the S1 poistion loaded via my file *.sys.

Please, can you help me to find this array (invtag) or desactivate the sorting only when I want to load the interactions file.

Hi Christoph,
I want to modify source code which can calculate net force on whole mesh moving in granular particles. That mesh is spherical type. Currently, we can measure force on triangles of the sphere. Can you give me some hints for doing this?
Thanks,
Ram