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[Jan Stránský <question694379@xxxxxxxxxxxxxxxxxxxxx>]

Question #694379 on Yade changed:
https://answers.launchpad.net/yade/+question/694379

    Status: Open => Answered

Jan Stránský proposed the following answer:
Hello,

> I would like to further isotropically compress the cropped dense packing with additional two boundary walls.
> I want to maintain the initial thickness of the packing and all the particle position.

Either you "maintain the initial thickness of the packing and all the
particle position" or "isotropically compress the packing", not both (as
you already realized).

Basic dualism in mechanics, either you know/prescribe displacement
(rotation,strain,...) or force (moment, stress,...), never both.

> I can imagine the reason behind this is that there are forces stored
at the grain contacts whenever it is compacted.

Yes, you saved not-stress-free (overlapping) packing, so after loading,
repulsive forces are computed (from the overlaps).

> So my question is how do I freeze the position of all the particles
without removing their original energy states and still reach the
desired state of isotropic compression?

no way (see above).

What is "their original energy states"?

In the second simulation, I see large gap between spherical particles
and walls. Why are there the gaps? They are reason that "all the
particles start to move around in any direction", so maybe reducing the
gap would make the simulation "nicer"?

cheers
Jan

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