yade-users team mailing list archive

[Luc Sibille <luc.sibille@xxxxxxxxxxxxxx>]

Hi Chiara,

In a general way, I think that one of the best answers is to read to PhD 
Thesis of Bruno where he checked in which conditions we can assume that 
the solution given by the DEM (which is a dynamic solution) for triaxial 
compressions is not very far from a static solution. However his thesis 
is written in French ;-)
Roughly speaking, the idea is to show that for sufficiently small 
loading velocities (but not too small otherwise the simulation takes to 
much time), the solution  given by the DEM is lowly influenced by the 
loading velocity. The "lowly" is fixed by what you think to be 
sufficiently accurate for the problem you study.
Then for practical and repetitive simulations you can check the 
unbalance force and verify that it corresponds to the unbalance force 
obtained during the parametric study to find the "sufficiently low 
loading velocity".
Maybe Bruno will tell you that you can directly reason from the 
unbalance force?

A slightly different approach, but consisting also to estimate the 
importance of the inertial terms through the dimensionless strain rate I 
can be found in:

@ARTICLE{dacruz05,
 author={da Cruz, F. and Emam, S. and Prochnow, M. and Roux, J.N. and 
Chevoir, F.},
 title={Rheophysics of dense granular materials{:} discrete simulation 
of plane shear flows},
 journal={Physical Review E},
 volume={72},
 number={2},
 pages =  "021309",
 year={2005},
 note={},
}

Regards, Luc

Chiara Modenese a écrit :
> New question #136034 on Yade:
> https://answers.launchpad.net/yade/+question/136034
>
> Hello,
>
> I would like to address you a question about static-equilibrium in dem simulations, with particular reference to PeriTriaxController engine. In the latter, how do we make sure that the static-equilibrium condition is maintained during the triaxial phase, for instance? Looking at the code, I see that the unbalanced force is checked only when the system has reached the prescribed goal condition. What is the best criterion to establish if the system is under quasi-static conditions? Is the unbalanced force the only solution?
>
> Thank you for your opinion.
> cheers, Chiara

--
Luc Sibille

Université de Nantes - Laboratoire GeM UMR CNRS

IUT de Saint Nazaire
58, rue Michel-Ange - BP 420
44606 Saint-Nazaire Cedex, France

Tel: +33 (0)2 40 17 81 78