LIGGGHTS® - Developer Forum

Hello everyone,

I'm trying to write a new compute script to throw in the src folder that sums up the magnitude of the contact forces in the system. I tried to basically copy compute_pair_gran_local.cpp since that file directly works with the contact forces, and in my new file I would put a compute_scalar command to output a single global value that I want. The problem I run into is that compute_pair_gran_local.cpp only allows a single simulation to have one PairGran object registered using the register_compute_pair_gran_local function.

Hello everyone,

imagine a belt conveyor, where only one side along the longitudinal axis would have to be modelled.

Is there a way to model a symmetric boundary condition with LIGGGHTS?

Best regards,
MiRa

Hi, everybody

Hope everything is going well.
I noticed that the group option is allowed in fix property/atom
However, it is ignored in fix property/global automatically.
Wonder if it's possible to modify the source codes, so that I could use fix property/global with atoms in different groups?
Many thanks.

Best Regards,
Renge

Hello,

I am trying to modify the hertz contact model to include an adhesive force. So far I have hard-coded the modifications into the normal_model_hertz.h, which works fine. Now I want to do some parameter analysis and it would therefore be more convenient to define the relevant parameters in the LIGGGHTS script.

Let's say I want to define a matrix property, surfaceEnergyDensity, to be used. Below I included the modifications I did to normal_hertz_model.h and global_properties.cpp. I attached the log file.

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I'm now stuck trying to calculate the time-rate-of-change of pebble overlap, d(deltan)/dt, in order to create a kind of 'viscous damping' term in a contact model.

I've looked through lammps developer guide and there are walkthroughs on how to grow an array to grant access per/atom properties from previous timesteps (i.e. position, velocity, etc.). But contact information is a little more difficult because I have to use something similar to the tangential_model_history where there's a flag for contact, so I can't just create some generic array that maintains all overlap values.

Hello everybody,

I have made some adjustments in the contact models to suit my purpose but that included hard coding a length into the tangential history model.
I have decided now to switch the unit system from si to nano and I was wondering if there is a way to set a value depending on the unit system.
Here a code example showing the idea:

if (units=="si"){
adjustLen = a;
} else if (units =="nano"){
adjustLen = b;
}

I just don't know how to access the units. Can anybody tell me?

Regards
VBaric

Someone please provide procedure / steps for this.

Are we to simply place the files we edited / wish to add in the 'src' directory of the downloaded source files and compile??

Thanks,

Nasser

Hello all,

disclaimer: i've only just begun learning c++ so please correct me when I use the wrong syntax...

I'm trying to build a new normal model that has temperature dependence on the normal force. I created a new normal_model_etc based on the standard hertz file. I've done the first few modifications and tested that up to this point i can actually compile LIGGGHTS without error. But now I'm trying to access temperature and am not sure how to proceed.

Hi everyone,