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[Chiara Modenese <question186515@xxxxxxxxxxxxxxxxxxxxx>]

Question #186515 on Yade changed:
https://answers.launchpad.net/yade/+question/186515

Chiara Modenese proposed the following answer:
On 02/02/12 10:21, Chareyre wrote:
> Question #186515 on Yade changed:
> https://answers.launchpad.net/yade/+question/186515
>
> Chareyre proposed the following answer:
> Chiara there is no restriction on the rotation itself. You can rotate forever.
> There is only a restriction on the maximum deviatoric strain. Be it for simple shear or other types of diplacement field (even if all non-diagonal terms of velGrad are zeros), it makes no difference.
Yes, that is what I meant, restriction on maximum strain (is not related 
to the rotation itself?). In fact is not just a problem of simple shear, 
you are right about that. However, I think that in simple shear is 
easier to see the concept of continuous flow.
> For continuous shear flow, I see what you mean... You can plot it in a box with vertical boundaries but then this "window" is not periodic: below the bottom of this window, you won't find the top of the window. Hence it is physically not correct and, speaking of Yade, it breaks the collider's logic.
I am not sure to understand why the collider's should be affected by 
that. I think you are right to say that the solution may not be 
consistent. Maybe the only alternative is to use a 2D periodic 
condition, having two rigid walls on the top and the bottom boundary, 
one of which moving horizontally to apply a shear deformation. This is 
what other researchers are doing but as in Yade we can apply a 3D 
periodic I thought that another solution could be found (and I think you 
give it here below).
> One solution is to shift the period back periodically (https://www.yade-dem.org/doc/formulation.html#approximate-collision-detection, see "flipCell"). There are still a few things to fix in the flipCell function, but theoretically it should work.
Great, I think that is what Giuseppe wanted to know (sorry, I forgot 
about this function!).
> To be honest, I don't understand the relation between Giuseppe's
> question and you reply Chiara...
I should have explained that Giuseppe is working in a UK University and 
so has been visiting me. He expressed his question in a way that was not 
quite understandable (he has just started his final year project) and so 
I tried to formulate the question again (and give the answer as I 
thought) asking you for help.

Cheers,
Chiara

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