yade-users team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

Hi,
I discussed that with Raphael before and I was not sure it was worth
keeping the existing equations.
One reason is it is listed red here:
https://yade-dem.org/wiki/ConstitutiveLaws (i.e. no user and no
maintainer...)

I'm glad to hear that somebody can vouch for the current code and that
it corresponds to a published model (it would be nice to mention it in
the documentation).

In that case, of course, I agree with Anton's suggestion to keep the two
formulations available based on an optional argument.
The shift to FrictPhys inheritance is for good, as it will increase the
overall compatibility of materials (e.g. it will be possible to mix
FrictPhys and ViscElMat in the same problem without any additional functor).

Thank you Raphael for clear explanations. I'm inclined to consider that
you are becoming the maintainer of this code since you will be working
on/with it in the coming years (unless any other volunteer raises a
hand). Don't forget to append your name in the header of the files,
below previous author:
// 2009 © Sergei Dorofeenko <sega@xxxxxxxxxxxxxxxx>
// 2013 © Raphaël ...

For creating patch, see
http://jungels.net/articles/diff-patch-ten-minutes.html

@Anton, do you recommend "diff" or "git format-patch"?
@Raphaël, are you registered to yade-dev list? It is a good place for
such discussion.

Cheers

Bruno



On 22/08/13 17:16, Anton Gladky wrote:
> Question #234450 on Yade changed:
> https://answers.launchpad.net/yade/+question/234450
>
>     Status: Open => Answered
>
> Anton Gladky proposed the following answer:
> Hi Raphael,
>
> the law is written on the basis of this paper [Pournin2001]. Mass is
> used there. So breaking the already implemented contact model is
> highly bad idea as it will influence the results of people, which are
> already using it.
>
> Anyway, we are open to accept any contribution, so, please, provide a
> patch, which you want to commit and we will try to find a suitable solution
> for you.
>
> Recently I implemented this contact law in LIGGGHTS-code and I added
> "explicit"-parameter, which removes "mass-variable" if it is set. We can
> probably do it and for Yade as well,so you will be able to set strength and
> damping coefficient explicitly.
>
> Cheers,
>
> Anton
>
> [Pournin2001]L. Pournin, Th. M. Liebling, A. Mocellin (2001),
> Molecular-dynamics force models for better control of energy
> dissipation in numerical simulations of dense granular media. Phys.
> Rev. E (65), pages 011302. DOI 10.1103/PhysRevE.65.011302
>
>
> 2013/8/22 Raphaël Maurin <question234450@xxxxxxxxxxxxxxxxxxxxx>:
>> New question #234450 on Yade:
>> https://answers.launchpad.net/yade/+question/234450
>>
>> Hi all,
>>
>> I am using Yade in order to simulate bed load transport, i.e. granular flows driven by a turbulent fluid shear stress. For that, I am using the contact law Law2_ScGeom_ViscElPhys_Basic to take into account the dissipation occuring at contact in this dynamic situation.
>>
>> I modified this contact law, in order to make it be like the classical spring-dashpot law which is used in granular flow modelling, and I want to commit this changes. However this modification induces a change in the calculation of the equivalent contact stiffness and damping. In particular, I removed the weighting by the particles mass of the spring (and damping) contact parameter (it gave k = (m1k1 m2k2)/(m1k1 + m2k2)), which was surprising (not homogeneous to a stiffness/damping) and does not correspond to the classical spring-dashpot law (which is rather k = (k1 k2)/(k1 + k2))
>> I did some other changes, mainly to make the ViscElMat class inherits from FrictMat, which changes the formulation (young and poisson modulus instead of normal and tangential stiffnesses) but does not affect the physics.
>>
>> My question is then : Is anyone using this law ? Is it a problem for anybody if I commit this changes ?
>>
>> Thank you,
>> Best regards
>>
>> Raphael
>>
>>
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-- 
_______________
Bruno Chareyre
Associate Professor
ENSE³ - Grenoble INP
Lab. 3SR
BP 53
38041 Grenoble cedex 9
Tél : +33 4 56 52 86 21
Fax : +33 4 76 82 70 43
________________