yade-dev team mailing list archive

[Chiara + Eudoxos <chiara+eu@xxxxxxxx>]

Hi there,

first of all I suggest that you change your e-mail name to read Jan (not
Honza) since people not familiar with the Czech language must be
confused about your double identity.

> how can I rewrite in C++ this Python statement?
> 
> for i in O.interactions:
>     length = (O.bodies[i.id2].state.pos - O.bodies[i.id1].state.pos).norm()
See Shop::normalShearStressTensor. To make it independent on IGeom type
and working for both periodic and aperiodic boundary, you must compute
the distance from particle's position where the second particle is moved
by the "shift2", which is something like
scene->cell->Hsize*I->cellDist.cast<Real>(). (cellDist is a Vector3i,
that is why it must be cast to Real (Vector3r) for the matrix-vector
product to be syntactically correct).

> Or is there any other possibility to compute length of interaction in ScGeom (or in GenericSpheresContact in general)? I would like to use function Shop::stressTensorOfPeriodicCell() in new version of peri3dController when it is tested, but currently this function is written only for Dem3DofGeom..
Great, great!

We were actually just thinking, since there are now 4 implementations of
computing stress tensor (one by Bruno in PeriTriaxController, another
one by you in Peri3dController, your last one in
Shop::stressTensorOfPeriodicCell and the last one by us (following
Thornton) in Shop::normalShearStressTensor), it would be nice to show
analytically that they are identical by doing some index gymnastics.
Jan, you are very good for this kind of things, could you try to do
that?

If they are the same (they should be), we could make one single
implementation; ideally, it would be able to provide both normal/shear
and summary tensor.

A choice left for the user is whether one takes the current contact
length (particle distance) or the "reference" contact length (r1+r2 for
ScGeom, refLength for Dem3DofGeom) as the particle distance. I don't
know if some has ever compared results from both; and it has to do with
the unfamous granular ratcheting as well.

Cheers, enjoy your time!