yade-dev team mailing list archive

[François <francois.kneib@xxxxxxxxx>]

Ok I'm going to do the second option.
I talked with Raphael and I remember that his work was mostly focused on
the timestepper. But what I can see in the timestepper now is that he
didn't prepared the case of coexistent viscous and "pure" elast contacts in
the same simulation. So if the user sets the flag "viscEl=1" in the
timestepper, the code will do :

*ViscElPhys* viscPhys = YADE_CAST<ViscElPhys*>(contact->phys.get());*

for each contact, which is a problem for all non viscous contact -> segt
fault.

About K and Young, my precise idea is :

   - Ip2_FrictMat_FrictMat_FrictPhys : will use young and poisson directly,
   or use kn and ks if they exist and are set by converting them with : Young
   = 0.5 * Kn * R and Poisson = Ks/Kn. If both modulus and stiffnesses are
   defined for one material, print a message that gently recommend the user to
   review his script.
   - Ip2_ViscElMat_ViscElMat_ViscElPhys : will use Kn and Ks directly if
   they are set, convert and use Young and Poisson otherwise. If both modulus
   and stiffnesses are defined for one material, print a message that gently
   recommend the user to review his script.

About your warning, should I take care about something more ? I think that
kwargs are automatically handled  between python/c++ by boost.


2013/12/16 Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>

>  My vote for 2°).
> The independancy of the "Visc" classes makes no sense. It is inherited
> from very early ages of the code.
>
> Raphael partly fixed the problem regarding kn vs. Young. You should talk
> to him (I don't remember now why he did not make the inheritance Frict ->
> ViscEl - to minimize the noise most probably).
> There is now a choice to decide if kn should be translated like Young or
> not (IIRC).
> Your suggestion is to make it more transparent, the flag being set
> depending on which attribute is defined. I like the idea.
>
> Be carefull it must work with different syntax:
> mat.young = ...
> m=ViscElMat(.....,young=...)
>
> B
>
>
> On 16/12/13 08:56, François wrote:
>
>  Hi everybody,
>
> I would like in my simulations to make possible the interaction between
> (Coh)FrictMat and ViscElMat spheres. I don't want to activate the cohesion
> so I would let CohFrictMat become FrictMat by inheritance. The idea is to
> study the granular flow of viscous grains with one of the boundary made of
> cohesive spheres who sticks together.
>
> I think there are two solutions : the first one seems easier because it
> just adds a new class, but the second one (which modifies a little the
> viscous classes logic) may deserves our consideration. The choice between
> one of them is the subject of my question.
>
> 1°) Create a new class : Ip2_FrictMat_ViscElMat_FrictPhys(). This functor
> would make an interaction physic just like
> Ip2_FrictMat_FrictMat_FrictPhys(), ignoring the viscosity and converting
> the young modulus of the frictional sphere to a stiffness.
>
> 2°) ViscElMat, unlike its name lets believe, doesn't inherit from
> ElastMat. The main reason I think is because a ViscElMat has stiffnesses
> {kn,ks} while an ElastMat has a young modulus and a poisson ratio
> {young,poisson}. FrictMat inherits from ElastMat, and the only additional
> attribute it has is the friction coefficient. As ViscElMat has a friction
> coefficient too, don't you think we could make ViscElMat a child of
> FrictMat ? To avoid breaking people's scripts, we can imagine that if the
> user sets {kn,ks}, those parameters will override {young,poisson} in the
> calculation of resulting contact stiffnesses. With this inheritance, and if
> the user sets at least {young,poisson} for both his FrictMat and ViscElMat,
> the contact will be possible between :
> - FrictMat + FrictMat => FrictPhys
> - ViscElMat + ViscElMat => ViscElPhys
> - FrictMat + ViscElMat(FrictMat by inheritance) => FrictPhys
>
> Can people working with/on visco-elasticity give their opinion ? (Anton,
> Raphaël ...)
>
> Thanks,
>
> François
>
>
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> --
> _______________
> Bruno Chareyre
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