yade-users team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

Janek Kozicki a écrit :

> Feng, Chen said:     (by the date of Mon, 28 Nov 2005 22:21:02 -0500)
>
>  
>
> >    I am currently concentrated on the convergence criteria of the sphere 
> > system in YADE, for example, like in ITACSA's PFC2D software, the convergence 
> > criteria is that when the maximum unbalanced force is less than a certain 
> > value, the whole system is considered in equilibrium,
> >    
>
> I'm not sure if I understand 
I suspect you don't ;).
Let us not CC = convergence criteria, so that CC=0 <=> static equilibrium.
How to define such a CC?

Simply compute the sum of all forces on a body. At equilibrium, sum of all Fi on body Bk is 0. If you sum now on all bodies, you still have 
sum of F over all i and k equal to 0 (SFik = 0).
If SFik != 0, you are not at equilibrium.
If you normalize SFik dividing it by the mean value of F, you have the classical definition of CC.
CC is often used to verify that (1) a collection of bodies as reached a stable state (e.g. spheres of the ImpactTest) or (2) a simulation is not far from quasi-static conditions. And it is very easy to compute!

Bruno


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Chareyre Bruno
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