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[Jérôme Duriez <question293247@xxxxxxxxxxxxxxxxxxxxx>]

Question #293247 on Yade changed:
https://answers.launchpad.net/yade/+question/293247

Jérôme Duriez proposed the following answer:
Hello,

You mix here "geometry" [1] and "physics" [2] of YADE interactions. In
order to describe interactions in DEM, you need to know:

- what is the relative movement between two Discrete Elements (i.e. YADE
bodies), that's what's inside the "geometry" of the interaction, often
denoted i.geom

- how forces are associated to these relative displacements, i.e. which
contact law, that's what's inside the "physics" of the interaction:
i.phys

Ip2_FrictMat_FrictMat_MindlinPhys, like all "Ip2_" plays a role in describing the physics of the interaction (computing e.g. the stifness parameters of the interaction from the material parameters of the bodies). It has most often nothing to do with bodies shape !
Indeed, you can still use Ip2_FrictMat_FrictMat_MindlinPhys in your simulations whatever your shapes are, the only condition is that your bodies are of "FrictMat" type.
(I'm not 100% correct here, because of https://github.com/yade/trunk/blob/6d4a0d1689c6bad2dbdd6e27d1653418f7fc6498/pkg/dem/HertzMindlin.cpp#L43, but if you're new to YADE you may disregard this parenthesis that won't have any effect in your case...)

The bodies shapes enter into picture through the "geom". Because the way
e.g. overlap is computed depends whether we face overlap between
spheres, or between a sphere and a box, or between a sphere and a facet.

Your problem is thus (as Jan said: he told you about "Ig2", not "Ip2")
to use in your simulation the correct "Ig2_". Look here [3] (the names
do help !) to pick the right one.

Once this will be done, you will have a new kind of i.geom in your
simulation. For this reason, you may also have to update your "Law2_.."
(as Jan suggested again) which, in the end, has to consider both i.geom
and i.phys to do his job (computing and applying interaction forces)

Again, you will have to choose the correct Law2 (from [4], there is a
lot..., but again the names do help) to be sure it can handle the i.geom
and i.phys you have in your simulation.



[1] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.Interaction.geom, see https://yade-dem.org/doc/yade.wrapper.html#igeom for all possible choices
[2] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.Interaction.phys, see https://yade-dem.org/doc/yade.wrapper.html#iphys for all possible choices
[3] https://yade-dem.org/doc/yade.wrapper.html#igeomfunctor
[4] https://yade-dem.org/doc/yade.wrapper.html#lawfunctor

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