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[Jérôme Duriez <question668315@xxxxxxxxxxxxxxxxxxxxx>]

Question #668315 on Yade changed:
https://answers.launchpad.net/yade/+question/668315

    Status: Open => Answered

Jérôme Duriez proposed the following answer:
Hi,

I did not completely get you :-)

This being said, assuming your concern is about the line
https://github.com/yade/trunk/blob/master/doc/sphinx/tutorial/03
-oedometric-test.py#L51 (and the comment L50) that is reflected in https
://yade-dem.org/doc/tutorial-examples.html#oedometric-test:

This line and the choice and of a 5000 step number is only motivated by
the fact unbalancedForce is not a correct equilibrium (in the sense
resultant force on particles ~ 0) indicator at the start of a simulation
where no / low contact forces exist.

Then some iterations (5000 here) are performed regardless of
unbalancedForce() to allow some non-zero contact force / non-zero stress
state appear in the numerical sample, making unbalancedForce() useable
from this point onwards.

I'd advice you try to skip this "if O.iter<5000: return " kind-of
exception in your general workflow (once your simulation exhibits some
stress state).

Note running a (unknown beforehand) number of DEM steps until equilibrium can also be done with
while unbalancedForce() > yourThresholdValue:
    O.run(500,True) # you can use plenty of other values instead of 500

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