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[Jérôme Duriez <question264456@xxxxxxxxxxxxxxxxxxxxx>]

Question #264456 on Yade changed:
https://answers.launchpad.net/yade/+question/264456

    Status: Open => Answered

Jérôme Duriez proposed the following answer:
Hello Damien,

Indeed, in this new version of script, I understand you re unhappy with your spherical aggregate imploding. Which was not the case in the first version of the script, where, like Bruno, I do not see any problem.
Do not hesitate to state such things, so that we understand more what's going on along this thread.

If one script is "OK", and the other is not, the first thing to solve
your problem is to check what differences exist in both scripts ! ;-)

You're telling us about higher "Young" parameters. It is not the reason.
Just put in the second script E=50e7 (like in the first one), and you will still get this annoying behaviour.
Note that with numerical instabilities problem, spheres generally fly to the moon, while here they stay in the range of the graphical view. So, it is probably (surely in fact) not an instability problem related to excessively high stiffnesses. Which is logical since you're using this GlobalStiffnessTimeStepper which "is very efficient to set a convenient time step", as I said before.

On the other hand, you do not tell us about other differences between both scripts
- you changed the "gap" value of pack.regularHexa
- you added these lines
 for i in O.interactions:
 i.phys.unp = i.phys.penetrationDepth

Why ? And why did you want to reset zero contact forces (in fact I have
an idea, but it would help that you state it yourself ;-) )


For your other question (better open different Launchpad questions when you have different questions), the contact force of a given interaction "i" is accessed with
i.phys.normalForce. "i" being a member of O.interactions (see https://yade-dem.org/doc/yade.wrapper.html#interactioncontainer)
Or, more simply, through the "Interaction" tab of "Inspect" window of Yade graphical interface.

Jerome

PS : if you are yourself lost to identify changes between scripts, you may use "kompare" a nice software
PPS : providing scripts hoping that others will test and dig into them is a great favour you are asking. You will have more chance to get this favour removing as much stuff as possible from your script.
E.g. the definition of a zero gravity, and of a Translation Engine, which is not related to your problem

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