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[Jan Stránský <question685203@xxxxxxxxxxxxxxxxxxxxx>]

Question #685203 on Yade changed:
https://answers.launchpad.net/yade/+question/685203

Jan Stránský proposed the following answer:
Hello,

>> it is a free fall. Do you want them to behave differently? Why? How?
> why a particle (for example) which is on a side and is completely free, does not fall freely? apart of the others?

This I did not get it. I have tried it, and all particles (dark green in Yade GUI) falls uniformly. Is this wrong?
Please be more specific what "on a side" and "completely free" mean.. From my point of view, all dark green particles are "completely free" (before touching the ground)..

>> - time step of the simulation is low
> If I increase time step, model will explode. (I checked! Particles do not have overlap.)

I did not mean to increase it, it is just a feature of explicit time integration.
As Bruno said, its critical value depends on stiffness and density. Without hacking the physics of the problem (changing density or stiffness), there is no way how to improve this..

>> Better idea is to increase time step for the phase with no collisions.
> I do not understand your mean about the phase with no collisions (I am an amateur) ! When should increase time step?

phase with no collisions = the free fall phase (all bodies fall uniformly)
You do the same as you describe:
> For saving time, when the particles are moving down, I increase the gravity to 100000 (with simulation inspect window) for fast movement and when they are near the ground, I set real gravity.

but instead of increasing gravity, you increase time step and near the
ground you set it to stable value.

cheers
Jan

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