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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 3 June 2011 09:10, 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:
>
> >>> it as well? We could take the size of the cell as a reference (Radjai's
> >>> suggestion).
> >>>
> >> So I missed it (which page?).
> >>
> > Page 168, hope I read well... Let me know what you think.
> >
>
> Page 168 was written by my colleagues Gaël Combe and Jean-Noël Roux
> (while I was searching cell's mass in Radjai's PBC chapter) .
>
Oh sure, sorry if I confused the names.


> I got a chance to discuss the issue with them this week. Actually, when
> I asked which mass should be used, the first reply was "use a value that
> makes it work"... ;-)
> But still, this chapter suggest a definition that is dimensionally
> correct, you could try it.
> There is no need to change anything in the code, since it's up to you to
> give the "mass" value in your scripts. If you find that this definition
> is well suited, we can maybe hardcode it in the cpp later, so that
> "mass" will be totalMass/L by default (and include a mass factor to let
> users modify it if needed).
>
> Independently, I would keep the damping factor as it is now, since in
> perfectly elastic situations, eq. [6.7] would oscillate forever.
>
OK.

>
> In the end it would give:
>
> strain_rate[axis] += dampFactor*dt* ( goal[axis]-stress[axis] )
> *Length/(totalMass*massFactor); //massFactor=1 by default
>
I will try it. My conclusion is that probably it does not really matter how
you actually define your gain parameter, given that it works. However, it is
obviously good to have an idea (estimate) of what it could be and the above
line looks good to me. I will let you know. Thanks for your comments on
this.

Chiara

>
> Let us know if it works for you.
>
> Cheers.
>
> Bruno
>
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