LIGGGHTS® - User Forum

I have been running many simulations with a Lattice of granular particles with different CAD meshes interacting with them. There has been one major problem that i have not been able to figure out. When my timestep is any higher then 10^-7 gravity will pull the particles right through the bottom ZWall for no apparent reason. This results in the loss of all my particles after a short period of time. And they don't just fall out of the simulation, when they hit the bottom zwall the entire row of particles just disappears.

Greetings. I am attempting to run a simple compaction program of particles in a cylinder. I seem to get a successful packing of particles but they do not interact with the topwall as it moves down in the z direction. Using the cohesion and compression examples as templates, I have the following code:

#Contact model example

dimension 3
atom_style granular #diameter, density, angular velocity
atom_modify map array #processor stores lookup table of length N, N atoms. fast but limited by memory
boundary f f f #fixed boundaries in 3 dimensions

I am trying to achieve an adhesive force which is higher when two particles crash with higher velocity.
My idea was to change gamma_n. Therefor I want to use the Hertz/history/stiffness model. By looking at the equations I noticed that the equations for gamman and gammat looks different from Hertz/history because they don't use Sn and St.
Now I am not quiet sure how to calculate gamma_n and gamma_t.
It would be nice to get a short advice. Thanks.

command: git clone http://cfdem.git.sourceforge.net/gitroot/cfdem/liggghts myliggghts

error:
Cloning into myliggghts...
fatal: http://cfdem.git.sourceforge.net/gitroot/cfdem/liggghts/info/refs not found: did you run git update-server-info on the server?

plz help me out to solve this problem. i have also allowed port 9418 through firewall

I have an STL file that I want to pack with particles, I have noticed that the region command seems to only take .vtk files as input. Am I missing a parameter for an STL file or is this the case? Secondly, if it only takes vtk files then what programs are available to convert an STL to VTK file format? I tried saving the STL as VTK in paraview but it didn't seem to work properly.

Austin

Hi Christoph,

I've got a question about load balancing. In the pdf you uploaded (conference in Trondheim) there is something showed about load balancing. It seems already implemented into liggghts but I didn't find anything about it in the manual. Could you give me an advice where to find if if it is already implemented.

Hi everyone,

the case I am simulating consists of a bunch of particles stirred in a tank. The geometry of the stirrer is available in stl format.

I would like to calculate the torque exerted on the stirrer or the axle moving it, respectively. I've played around with fix mesh/gran/stressanalysis and its capabilities are almost what I need. Is there a way in liggghts to integrate the stresses such that I get the resulting torque on the axle?

Thanks for any comments.

Best regards,
Moritz

I have tried to calculate coordination number for a compact data-set with the command compute/cord/gran and got a very low number so I decided to write separate code and do this calculation. I considered two particles to be neighbors if their distance is less than or equal to the sum of their radii and got a reasonable result. I don't know why there is such a difference.

Hey Christoph,

I don't get where the coefficientFriction is used in gran/hertz/history formula, according to the formula given in pair_gran.html file there is no need to this quantity.