LIGGGHTS® - User Forum

Hello,
I am working on Triaxial Compression test on granular particles. I use servo walls for the compression.
The problem is initially the forces are high and my servo walls are in the input positions but as the forces approaches to the target val the particles push away the walls and my desired volume changes.
How to keep the walls in position with the target val. I don't want the walls to be fixed in the position through out the test as I want to observe a Volume increase or decrease during isotropic compression and under shearing.

Thanks,
Venkataraman

Hello, all.
I'm doing excavation simulate, to measure how much torque would appear.
I don't know why but all the time the buckets movement switches from move to rotate (rotate to move as well)
or to move meshes slowly, the torque suddenly drops. (not disappears)

Hello,

Does anybody know why when I change
fix id all property/global surfaceTension scalar "value"
or
fix id all property/global contactAngle peratomtyp "value"
I have a different distribution of particles in my pack.
And maybe you guys know how to keep it constant?
Here are my LIGGGHTS codes for CFDEM.

in.liggghts_run

echo both
log ../DEM/log.liggghts
thermo_log ../DEM/post/thermo.txt

atom_style granular
atom_modify map array
communicate single vel yes

Hi,

I am running the blending mixer example, but failed. There is the error message . Please find the attached file.

Could you help me to solve this problem.

Thanks

Hello,

I am interested in calculating the volume fraction of my particles after filling a hopper, so I was wondering how can I do that as my geometry includes curvatures.

So may you please help me in that.

best wishes,

Hi colleagues,

I am facing a problem about outputing the magnitude and average of contact force, but failed.
To obtain the contact force, I use command:
compute fc all pair/gran/local pos id force (the 10-12th values are the contact forces on x,y,z directions)

Then I use:
variable avefc atom sqrt(c_fc[10]^2+c_fc[11]^2+c_fc[12]^2)
to calculate the magnitude of contact force.

Hello all,

I need to invoke a python script during the run time of the simulation . The script has to be invoked in every timestep. Is there a possibility to do that?
I know the other way around (python->Liggghts) is possible. But I need to compute some paramaters outside liggghts at each and every timestep and I need to use that data again in the simulation. So please suggest me some ideas on this.

Thank you .

Hi everyone,

I have recently implemented a modified heat conduction model in LIGGGHTS. If anyone is interested in using and discussing about this piece of work, uploaded in ArXiv, https://arxiv.org/abs/1809.01379, please drop me an email weijing.dai@sydney.edu.au.

Cheers
Weijing

I have read the paper by Podlozhnyuk et al. (2017) and curious about the contact force calculation.

Referring to Fig. 6, it is shown that different results of adopting different radius method.

And I have written a script to examine the results.

However I have got the results of the volume equivalent sphere. And I could see the big difference from the FEM results if I keep increasing the overlap.

Is there any comment on it?

Or it would be appreciated if you could give your experience on examine it?

Kind regards,

Hello,
Is there a way implement a particular force exerted from the fluid side on the particle to be integrated using implicit time integration, ASIDE from the dragforce. It seems there is a possibility to integrate ONLY the drag force implicitly:
https://github.com/CFDEMproject/LIGGGHTS-PUBLIC/blob/master/src/fix_cfd_...