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[Chareyre <question136034@xxxxxxxxxxxxxxxxxxxxx>]

Question #136034 on Yade changed:
https://answers.launchpad.net/yade/+question/136034

Chareyre proposed the following answer:
>> 1.a) PeriTriaxController (with dynCell=True) is not confounding statics and dynamics : it
>> is purely dynamic.
> Eh, that is exactly what I said...

I got it.

>I meant that choice of a suitable staticity criterion depends on what 
>type of damping is employed.

Not so, if you mean staticity criterion like "I want error on sigma<10e-3 in the
simulation", and this is how  unbF is usefull.
If you set damping higher, or if you modify the damping method (keeping loading rate
constant), it will be reflected in unbF. So, you can adjust the loading rate in order to
keep unbF constant, and expect the same order of error.
Of course, it needs prior tests to decide what unbF correspond to this 10e-3 error on
sigma, but this is required anyway whatever the non-staticity measurment.

> Eh, alright.... I think this has become too confused a discussion to be 
> meaningful.

I think the important point is :
Non-staticity is affected by physics but also by numerical artifacts, coming from the
integration scheme (the "numerical wave" part), affecting the relaxation delay, and
affected by the number of grains. The latest is dominant in the quasi-static regime for
large number of grains. Hence, applying energy concepts (or more generally physics) for
this question is not fully adressing the problem, and it will not replace numerical
experiments.

Bruno

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