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[Jérôme Duriez <question660590@xxxxxxxxxxxxxxxxxxxxx>]

Question #660590 on Yade changed:
https://answers.launchpad.net/yade/+question/660590

    Status: Open => Answered

Jérôme Duriez proposed the following answer:
I still did not grasp/look at all details but it is surprising to me you
get sometimes a resultant force "force" = O.forces.f quite "high" (~ 1e4
which is the "constant" value you're expecting in the 2d simulation),
and a much lower value  (~10...) in the 2d simulation with a lower
damping. Are you actually considering equilibrium configurations ?


As for the four normalForce, the reason should be clear: there most probably is 4 interactions in one case, and 2 in the other.
I do not know the reason for this discrepancy in terms of interaction numbers but this means your two simulations are not comparable.


On a general note, being sure one should get the same results between the 2 simulations needs a full understanding of all operations of the YADE (DEM) loop. 

By deleting / re-inserting bodies, you also delete / re-insert
interactions. Considered with the fact that some information in DEM take
one step to "propagate" (this is kind of a vague sentence, I agree, but
it's almost the week end), I would not be surprised if you get one step
offset between the evolutions of the two cases...


Just some ideas

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