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[Chareyre <question141044@xxxxxxxxxxxxxxxxxxxxx>]

Question #141044 on Yade changed:
https://answers.launchpad.net/yade/+question/141044

    Status: Open => Answered

Chareyre proposed the following answer:
CN below 4 is quite common, and expected.

Think isostaticity :
-There are 6 equilibrium equations.
-One frictional contact is blocking 3 DOFs.
Then, strictly speaking, a particle can be stable with 2 contacts (in
fact 3, in order to block also rotations). CN=4 is impossible except in
very special cases.

If friction=0, the contact is blocking only one DOF : it needs 4
contacts to really block one particle (with 3 contacts, it could
detach). Rotations will never be blocked. So you would get exactly CN=4
in that case (modulo elastic deformation creating contact if the ratio
pressure/Young is high).

Note that CN gives no indication on the stability of a packing. You
can't say "it is stable because CN>something".

HTH.

Bruno

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