Hi,
I seem to have a strange problem: I started using LIGGGHTS for high velocity particles (O(100m/s)) but somehow LIGGGHTS is not able to resolve wall impacts - particles are just leaving the geometry. The geometry is given by an stl-file (which is completely inside the defined region/domain). The timestep is far smaller than radius/max_velocity and the whole simulation runs just fine for smaller velocities. Different contact models etc were testes but the fact that the particle velocity seems to be the crucial parameter gives me the feeling that somehow particle do not see the walls - maybe because the walls/particles list were not updated often enough?
Did anybody experience similar problems?
Best Regards
Stephan
Riccardo Maione | Thu, 04/26/2018 - 15:38
Hello Stephan,
Hello Stephan,
maybe it is best if you attach the input and mesh files, however you should check the young modulus because with these particles velocity if the young modulus is low the deformation can be so high that it causes particles going through walls..
Regards,
Riccardo
medvedeg | Thu, 04/26/2018 - 19:06
Hi Stefan,
Hi Stefan,
1) Did you check the ratio of the time step to Hertz time? https://www.cfdem.com/media/DEM/docu/fix_check_timestep_gran.html can help you
2) I am not sure if DEM is valid at such collision velocities (100m/s)
Stephan | Fri, 04/27/2018 - 10:21
particles leaving geometry ( high velocity)
Hi,
thanks for both answers - I will check that as soon as I have time again. The time step check was already done (no problems) and I dont see any general problems with high velocities in a DEM-setup. But again thanx for helping me!
Best Regards
Stephan