Does LIGGGHTS have a compute style to calculate the total unbalanced force in the system? Or better yet, a ratio of the total unbalanced force to the sum of all the contact forces? I use such a ratio in other programs to determine whether my simulation has reached a stable state, and I'd like to move onto using LIGGGHTS now.
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ckloss | Fri, 10/14/2016 - 14:54
Hi Estefan,
Hi Estefan,
you can use the compute com to get the center of mass of the particles in the system. This is a very good metric to assess if the system is steady state.
From the total mass in the system and the change in COM you can also calculate the unbalanced force if your want
Christoph
estefan31 | Fri, 10/14/2016 - 19:52
Just so I understand your
Just so I understand your suggestion correctly, is steady state determined to be when the center of mass is no longer changing significantly? So maybe say steady state is achieved when the center of mass changes by 0.1% between two timesteps or something like that? And in case this changes anything, I have an unsymmetric system with gravity so I don't expect the center of mass to be at the geometric center.
ckloss | Fri, 10/21/2016 - 15:29
Hi Estefan,
Hi Estefan,
center of mass not changing is definitely a necessary condition for steady state, but not necessarily a sufficient condition - think about systems with heat transfer for instance. You'll have to check if it is sufficent for the type of system your're looking at, but typically it works pretty well
Christoph