LIGGGHTS® - User Forum

Dear all,
i'm trying to use the fix massflow/mesh with liggghts version 2.3.6 and get a segmentation fault after some timesteps. My setup to test and reproduce the message is a simple cube without a bottom or lid. Some atoms will be placed inside, fall down and leave the box throuth the bottom and re-enter the box from above (since there is a periodic boundry in z-axis).

I attached the testcase with my liggghts script, the logfile and two mesh files. Please remove the ".txt" extension before using it.

Many thanks in advance!

Cheers,
Daniel

Hi all,

When I perform a hybrid simulation (granular-peridynamics), I observe in the pair_gran_h*.cpp that the mass of the particle (rmass) is equal to the density.

If I try to fix the problem from the file loaded by the command read_data, it's worse !!!

So, if I compute the mass of the particle into the file pair_gran_h*.cpp, Do I have to take care to affect the good value of the mass in an other file ?

Or Have you a simple way to fix this problem ?

Thanks in advance for your request

Regards
JF

Hi!

I want to use some of the output variables of LIGGGHTS, such as fx or x, for a range of particle. I want to make some calculations in the input file for, finally, export them at the dump file.

However, I don't know how to call and store them in an array.

Thank you for your help!

Ramon

I tried to make one of my mesh accelerating with time, so after digging in documentation I found this fix move/mesh linear/variable, however whatever variable I tried to put I constantly had an error:

"Variable name 1 for fix move/mesh linear/variable does not exist"

an error comes from the file "mesh_mover.cpp" line 112 and it is natural consequence if something goes wrong in lines above.

Correct me if I am wrong but lines 97 to 110 in this file are not quite correct and as it is so, there always something is going wrong.

I have a question about pair_style. I'd like to simulate solid materials such as shale, clay, sand, and like this. I need to know what the appropriate pair_style for doing that is?

Another question is about integration. In my project I have to decrease temperature from X1 to X2. How can I do that?
And using "fix integer nvt/sphere temp X1 X2 DX" is true or not?

Thanks a lot for the response in advance.

For doing a project I face some unknowns.

The one is that I want to simulate crack propagation in shale (a type of
sand) and investigate crack pattern in shale if I decrease the temperature by LIGGGHTS. I need to know how I can decrease it (temperature of the simulation box)?

Second is that do you know the material properties of shale?

The easiest way is to fix the temperature of some particles, I need to know how I can set it to a certain temperature every few time-steps?

Thanks a lot for your attention in advance.

Sincerely,
Rasoul

Hello everybody!

I was running my first simulation in LIGGGHTS and it appears one error message when it is reading the mesh archive of the bottom of my geometry. The content is:

I've a question about computing the maximum contact force
I know I can get the pair-force with
compute 2 all pair/gran/local force
But How to calculate the magnitude ?
(I tried variable fmag atom sqrt(c_2[1]^2+c_2[2]^2+c_2[3]^2) but got ERROR: Mismatched compute in variable formula)

Next problem is how to find the maximum of fmag, I tried
variable fmax equal max(fmag)
but got "ERROR: Invalid special function in variable formula"

Hi Chris,

I created a large region compared to the radii of particles, and the time-stepping becomes very slow.

region reg block -0.01 8.1 0.0 1.51 -0.01 4.51 units box

The particles radii varies from 0.008 to 0.016, and total # of particles is 10k. So the region is mostly empty.

I tried using shrink-wrapped "boundary s s s" but the issue remains.

Hello everyone,
I have been using Liggghts for a couple weeks and I have already done a simple shear test but now I want to do a triaxial test. I read about the servo control walls but since the test is a cylindrical moving boundary I dont think that is a proper boundary because of two reasons:
1. The walls are rigid boundary and in reality they are flexible.
2. I can not think of moving the cilindrical walls with out changing the shape or leaving a gap.