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'Hanging" particles


Hi, all!

As I wrote before, I met recently the "hanging particle problem". Will try
to shortly explain, what I mean.
I throw the stone into the "machine" (init.png). Stone is the set of
cohesive particles:

1) When I use contact damping, *cundallDamping = 0", all is working as I
await, the stone destructs after machine rollers crack it. (contact.png)

2) When I use Cundall's non viscous damping = 0.3, for example, and
contactDamping=0, I have a very strange result. The specimen (stone) falls
down (gravity), crashes partially and then stops at machine. It begins to
"hover" above the machine, hanging. After impact I get this strange
behavior. It seems, like the gravity does not work after impact. Machine is
continuing to work, but the stone hangs. (cundall.png)

Contact damping satisfies me completely. The problem is that there is no
energy dissipation after impact, that is why I have "flying far away"
I wanted to add "drag engine" or "aerodynamic engine" to decrease particle
speed after impact. But after analyzing literature I learned, that on
relatively small velocities it will work exactly like our Cundall damping
mechanism works.

I would appreciate any comments and advices on this problem.
I will try "localize" the problem (decrease number of particles, simplify
the model etc...), but not sure it is easy.

What about if we use CundallDamping only on velocities, larger, than defined
value (just an idea)?

Thank you.

Anton Gladkyy

Attachment: init.png
Description: PNG image

Attachment: contact.png
Description: PNG image

Attachment: cundall.png
Description: PNG image

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