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[Jan Stránský <question702743@xxxxxxxxxxxxxxxxxxxxx>]

Question #702743 on Yade changed:
https://answers.launchpad.net/yade/+question/702743

    Status: Open => Answered

Jan Stránský proposed the following answer:
Hello,

thanks for the data

> 1) All plots have runs that start negative, which is not intuitive. I
feel they should all start at zero (or close to it).

You push "the object" down through the packing, which also is not vary intuitive..
At the end, you of course has some have some forces and torque on the object.
The orientation of the forces and the sense of the torque are basically random (due to just pushing down), possibly negative.

> 2) Sometimes results can be radically different (e.g.,
density_Sensitivity_Testing.png)

With this coarse spherical packing w.r.t. the object, I expect significant discrepancy w.r.t. initial particle packing.
Not the initial particle packing before the gravity deposition, which seems to be the same using memoizeDb, but the "starting  packing" after gravity deposition, which might differ (see below).

Check if you have same or different packing after the gravity
deposition.

> 3) Even when not radically different, the results doesn't make inherit
sense. I.e., spheres with less density can create more torque on the
object than spheres with a lower density.

what is density? Material density? Packing density?
If material density, then the packing difference is probably more significant for the results then the material density..


How do you run your simulation? Using parallel / multicore run, or not?
If yes, then you intrinsically get different results [1].
Specifically for your case, different "starting packing".
Even with same "starting packing", you simply get different results.

Cheers
Jan

[1] https://yade-dem.org/doc/formulation.html#result-indeterminism

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