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[Jan Stránský <question689409@xxxxxxxxxxxxxxxxxxxxx>]

Question #689409 on Yade changed:
https://answers.launchpad.net/yade/+question/689409

    Status: Open => Answered

Jan Stránský proposed the following answer:
Hi,

> young=4e8
> facetMat=O.materials.append(FrictMat(young=young
> I'm wondering what's the possible reasons that the particles go out the box, except for the timestep.

e.g. stiffness :-) try to increase stiffness of the walls

> maxDt = 0.6*PWaveTimeStep()
> O.dt=.5*PWaveTimeStep()
> even though I set the timestep smaller than the critical timestep and also limited the maximum timestep. the particles still go out of the container.

here I am betting on the stiffness, but in general a time step below the
critical value makes the simulation stable, but it does not necessarily
help in this problem - e.g. if by some circumstances the velocity of
particles is such high that it goes through the wall without even
detecting the contact, the critical time step has no way how to help in
this situation.

The factors 0.6 and 0.5 might easily be on the edge of the actual system
critical time step for dense packing. PWaveTimeStep just computes the
critical value for a single sphere-sphere pair, but in the dense packing
there might be several interactions "in the same direction", making the
system "stiffer" and you might need even lower value.

cheers
Jan

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