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[Jan Stránský <question702743@xxxxxxxxxxxxxxxxxxxxx>]

Question #702743 on Yade changed:
https://answers.launchpad.net/yade/+question/702743

    Status: Open => Answered

Jan Stránský proposed the following answer:
> Does a DEM simulation ever converge relative to the time step?

yes, it should, explicit time integration methods should converge for decreasing time step.
For deeper mathematics , discuss with some mathematician.

> any reduction in time step would produce the same results?
> the model still produces slightly different results for different time steps.

>From the plot, the difference seems pretty small to me, in the order of percents.
In general, you have a lot of influencing factors in DEM.
Obviously time step is one of them, practical values ("close" to critical time step) influences the results.
Then you have many other factors, e.g. the initial packing. If you change the packing, you get different results.
If you run simulation in parallel, you get different results (!) [1].

So **from my point of view** your plot seems pretty good.
**In my point of view** it is not a good idea to match exactly one simulation to one results, but rather a trends or some statistics from multiple runs if some "exact match" is needed.

Cheers
Jan

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