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Re: dissipating all energy in a packing


Hi Vaclav,

I am not sure that you can do everything with the DEM! You would like to have a quasi perfect static case by using a dynamic method... Whatever the method you use to damp particle movements I suspect the system to reach a vanishing value of kinetic energy asymptotically. Thus, if it the case, you can wait a very long time to obtain values of kinetic energy as small as you want...

But DEM is not the only method to perform discrete computations and static method based only on geometrical aspects without integrating Newton's law, allow to perform very accurate computations (for instance about the definitions of contact). See for intance the works done by Roux and Combe.

  Good luck!


Václav Šmilauer a écrit :

I need to reach as much as possible equilibrium state, with zero motion.
When using cundall's damping, I get kinetic energy dropping from 1e-3 to
1e-9, but not any lower. I suspect the cause to be the fact that
cundall's damping makes force greater against the current velocity; that
can lead to oscillations at the frequency of 2 iterations, if the force
is such that it reverses the sense of velocity during one interation,
then again etc. I suspect the same will be true for the unbalanced force

1. Is someone using some sort of viscous damping to avoid this?

2. I could try to make cundall's damping to always diminish the force
iff the coefficient is <0 (.e.g damping==-.3 would mean to always reduce
the force to ×.7), what do you think?

Regards, Vaclav

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Luc Sibille

Université de Nantes - Laboratoire GeM UMR CNRS

IUT de Saint Nazaire
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