Polyhedra-Sphere-Facet Coefficient of Restitution

> spheres do not appear to have any coefficient of restitution
> Right now it looks like Mindlin Law2 and Ip2 are ignored and everything is defaulting to CundallStrack.

please observe the actual state - inspect interactions and get the actual type of interaction.phys

> Ideally I'd like the polyhedra to use the mindlin physics as well

then why using CundallStrack at all?

cheers
Jan

Thanks for responding so quickly Jan!

When I remove Law2_ScGeom_FrictPhys_CundallStrack() from the interactionLoop I get the following error:

<FATAL ERROR> InteractionLoop:182 virtual void yade::InteractionLoop::action(): None of given Law2 functors can handle interaction #1273+2328, types geom:ScGeom=1 and phys:PolyhedraPhys=18 (LawDispatcher::getFunctor2D returned empty functor)
Segmentation fault

If I leave it in the loop everything is fine, but I get no coefficient of restitution.

How does one go about inspecting the interaction.phys? I suppose this needs to be done on the working script because the script without CundallStrack has a Segmentation Fault that kills everything.

Please create and provide a MWE [1] containing your InteractionLoop with all shape-material combinations you use, all bodies fixed (for the sake of simplicity), one iteration, all possible combinations of interactions are present (sphere-sphere,sphere-polyhedron,...).
With that MWE, we can easily/quickly test modifications.

The point is that such combination of "many" shapes and materials is not too frequent among yade users/developers and such cases are in general problematic (you can find some in the question history).

> How does one go about inspecting the interaction.phys?

something like:
###
print(set(i.phys.__class__.__name__ for i in O.interactions))
###

One workaround could be using Ig2_Polyhedra_Polyhedra_ScGeom [2] (instead of Ig2_Polyhedra_Polyhedra_PolyhedraGeom). I am not sure about the polyhedron-boundary interaction...

cheers
Jan

[1] https://www.yade-dem.org/wiki/Howtoask
[2] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.Ig2_Polyhedra_Polyhedra_ScGeom

This question was expired because it remained in the 'Needs information' state without activity for the last 15 days.

Hi Jan,

Sorry for the tardy reply. Ig2_Polyhedra_Polyhedra_ScGeom creates really strange behavior and sometimes crashes so that did not work. However, I did figure out how to get the spheres to use MindlinPhys instead of CundallStrack. I made the mistake of assigning the PolyhedraMat to the sphere material. When I changed the sphere material to FrictMat the spheres started using MindlinPhys.

The simulation looks much more realistic as long as most of the particles are spheres. I have one final problem: is it possible to make the polyhedra follow MindlinPhs too? I need them to have a coefficient of restitution as well.

Hello,

If you want all interactions to be of the same type, there is nothing easier :-)

Something like this could work:
Spheres - FrictMat
Polyhedrons - FrictMat
Facet - PolyedraMat
( there is currently no Ig2_Facet_Polyhedron_ScGeom, although it should not be difficult to implement it, then you could get rid of PolyhedraMat entirely)
and
InteractionLoop(
        [
            Ig2_Sphere_Polyhedra_ScGeom(),
            Ig2_Sphere_Sphere_ScGeom(),
            Ig2_Polyhedra_Polyhedra_ScGeom(),
            Ig2_Facet_Polyhedra_PolyhedraGeom(),
            Ig2_Facet_Sphere_ScGeom(),
        ],
        [
            Ip2_FrictMat_FrictMat_MindlinPhys(en=Restitution, gamma=Stickiness, krot=RollRes),
            Ip2_FrictMat_PolyhedraMat_FrictPhys(),
        ],
        [
            Law2_ScGeom_MindlinPhys_Mindlin(includeMoment=True, includeAdhesion=True),
            Law2_PolyhedraGeom_PolyhedraPhys_Volumetric(),
        ],
    ),

Have a try and let us know

> Ig2_Polyhedra_Polyhedra_ScGeom creates really strange behavior

ScGeom between Polyhedrons is an easy "hack", not too much tested etc.
If you can isolate the problem in a MWE (e.g. 2 specific polyhedrons with given initial velocities), please open a new question or new issue.

> sometimes crashes so that did not work.

Please be more specific (ideally again in an separate issue or question)

Cheers
Jan

I tried changing the polyhedra material to FrictMat and got the follow error:

"In [1]: <FATAL ERROR> InteractionLoop:182 virtual void yade::InteractionLoop::action(): None of given Law2 functors can handle interaction #919+3649, types geom:PolyhedraGeom=10 and phys:FrictPhys=3 (LawDispatcher::getFunctor2D returned empty functor)
<FATAL ERROR> InteractionLoop:182 virtual void yade::InteractionLoop::action(): None of given Law2 functors can handle interaction #920+3649, types geom:PolyhedraGeom=10 and phys:FrictPhys=3 (LawDispatcher::getFunctor2D returned empty functor)
<FATAL ERROR> InteractionLoop:182 virtual void yade::InteractionLoop::action(): None of given Law2 functors can handle interaction #915+3652, types geom:PolyhedraGeom=10 and phys:FrictPhys=3 (LawDispatcher::getFunctor2D returned empty functor)
Segmentation fault"

I get this error with both Ig2_Polyhedra_Polyhedra_PolyhedraGeom() and Ig2_Polyhedra_Polyhedra_ScGeom()

I'll see about building a MWE to illustrate the problem on Monday

Ok, probably you would need either
Ip2_FrictMat_PolyhedraMat_PolyhedraPhys
or
Ig2_Facet_Polyhedron_ScGeom
both not implemented. Ip2_FrictMat_PolyhedraMat_PolyhedraPhys should be easier (have a look on existing Ip2_FrictMat_PolyhedraMat_FrictPhys [3,4]).
Cheers
Jan

[3] https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/Polyhedra.hpp#L263
[4] https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/Polyhedra.cpp#L547

Hi Jan,

I finally found time to try out your recommendation. This is the function I created:

void Ip2_FrictMat_PolyhedraMat_PolyhedraPhys::go(const shared_ptr<Material>& pp1, const shared_ptr<Material>& pp2, const shared_ptr<Interaction>& interaction)
{
 if (interaction->phys) return;
 const shared_ptr<FrictMat>& mat1 = YADE_PTR_CAST<FrictMat>(pp1);
 const shared_ptr<PolyhedraMat>& mat2 = YADE_PTR_CAST<PolyhedraMat>(pp2);
 interaction->phys = shared_ptr<PolyhedraPhys>(new PolyhedraPhys());
 const shared_ptr<PolyhedraPhys>& contactPhysics = YADE_PTR_CAST<PolyhedraPhys>(interaction->phys);
 Real Kna = mat1->young;
 Real Knb = mat2->young;
 Real Ksa = mat1->young * mat1->poisson;
 Real Ksb = mat2->young * mat2->poisson;
 Real frictionAngle = math::min(mat1->frictionAngle, mat2->frictionAngle);
 contactPhysics->tangensOfFrictionAngle = math::tan(frictionAngle);
 contactPhysics->kn = Kna * Knb / (Kna + Knb);
 contactPhysics->ks = Ksa * Ksb / (Ksa + Ksb);
}

This does allow me to assign friction material to the polys. Unfortunately, I still seem to need CundallStrack or I get this error:

 <FATAL ERROR> InteractionLoop:182 virtual void yade::InteractionLoop::action(): None of given Law2 functors can handle interaction #8+239, types geom:ScGeom=1 and phys:PolyhedraPhys=18 (LawDispatcher::getFunctor2D returned empty functor)

as soon as the polys touch the facets. When I add CundallStrack the particles explode as soon as they touch the facets.

Maybe I need to try to create a Ig2_Facet_Polyhedron_ScGeom so everything uses friction material.

> Maybe I need to try to create a Ig2_Facet_Polyhedron_ScGeom so everything uses friction material.

you can try.. let us know if you need some help

Cheers
Jan