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[Chiara Modenese <question159394@xxxxxxxxxxxxxxxxxxxxx>]

Question #159394 on Yade changed:
https://answers.launchpad.net/yade/+question/159394

    Status: Answered => Open

Chiara Modenese is still having a problem:
On 31 May 2011 14:41, Chareyre <question159394@xxxxxxxxxxxxxxxxxxxxx>
wrote:

> Your question #159394 on Yade changed:
> https://answers.launchpad.net/yade/+question/159394
>
>    Status: Open => Answered
>
> Chareyre proposed the following answer:
>
> > To me they are conceptually similar (leaving the 0.8 coeff aside), with
> the
> > difference that there is no wallDamping in periodic case. Maybe I am
> > misunderstanding...
> That's right. In the periodic case, the equation imposes damping=0. If
> it were me, I would have include (1-damping) factor in the equation.
> If it is unstable, such factor could help relaxing the system (or in
> other words: reduce gain).
>
Good, you come with me then... So we are missing a relaxation factor there,
I believe.
Bruno, I had a look at your equation, again

strain_rate+=dampFactor*scene->dt* ( goal[axis]-stress[axis] ) /mass;

and we are missing a length here to be consistent with the unit of measure.
Radjai, in a similar equation he proposes in the book you mention, is in
fact considering a length divided by the mass parameter. Why do not we use
it as well? We could take the size of the cell as a reference (Radjai's
suggestion).

Chiara

>
> > Vaclav did not use it and Jan wrote his own controller, but I let him add
> a
> > comment on all of this (could not you add your opinion, Jan?).
> Mmmh... Let's see.
>
> Bruno
>
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