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[Chiara Modenese <question178830@xxxxxxxxxxxxxxxxxxxxx>]

Question #178830 on Yade changed:
https://answers.launchpad.net/yade/+question/178830

Chiara Modenese proposed the following answer:
On 17 November 2011 15:25, Christian Jakob <
question178830@xxxxxxxxxxxxxxxxxxxxx> wrote:

> Question #178830 on Yade changed:
> https://answers.launchpad.net/yade/+question/178830
>
> Christian Jakob proposed the following answer:
>
> > "O.interactions.clear()":
> > It will most probably break everything. As soon as collider stride
> > is used, interactions are not created at each step, then particles
> > will penetrate each other for a random number of steps without
> > interacting. To overcome that you could disable stride. Overall,
> > stride=off and deleting/creating all interactions at each step could
> > well multiply cpu time by 10.
>
> The creation of all contacts has only to be done once (after
> O.interactions.clear). Is there a command like
> O.interactions.recreate() ?
>
You should not use this function (O.interactions.clear()) at all in this
case, that is the main concept. As Bruno said, you do not want to loose the
history of shear forces (for instance). The use of this function is not
really an option for you (sorry again for wrong suggestion).
Chiara

>
> >
> > In addition, the history of the contact is lost, i.e. the tangential
> > force is lost, resulting in instabilities and artificial creep.
>
> Yes, but the script is just for generating the particles (model
> preparation).
> After this step the user can do what ever he wants (e.g. load it into
> a triaxial test).
>
> >
> > Concerning the initial problem of wangxiaolang: Yes, increasing sizes is
> > changing psd homotheticaly. If you want to impose not only the
> > dispersion around mean size but also mean size itself, then you have to
> > generate particles smaller than the target size. If you have target
> > porosity  and target final size, it is not difficult to derive how
> > smaller they should be initially. I guess you had to solve this problem
> > somehow in your script, since you are also increasing sizes after all?
>
> Yes, first the particles are decreased by factor f = 1/(a*b*c*d*e) and
> then they are increased by a, then by b, and so on. Finally they have
> exactly their target size.
> If one knows f in ThreeDTriaxialEngine, then the particles could be
> generated smaller before blowing them up. In this case it seems, that
> my script makes the same ...
> Can I use this engine without modeling any triaxial tests (as
> preparation step for my model)?
>
> cheers,
>
> christian
>
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