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[Jérôme Duriez <question672525@xxxxxxxxxxxxxxxxxxxxx>]

Question #672525 on Yade changed:
https://answers.launchpad.net/yade/+question/672525

    Status: Open => Answered

Jérôme Duriez proposed the following answer:
I think you correctly understood https://yade-dem.org/doc/formulation.html#motion-integration in terms of notation, except we use funny symbols (+/- with a circle around, instead of just 0,+,-) for velocity because you have to consider the velocity as being a value *at the middle* of a time step.
See the explanations in "Let us recall..."  of https://yade-dem.org/doc/formulation.html#motion-integration

You can call it "mean velocity" (during one timestep) if you want, this
point of view is  exact for a linear evolution of the velocity such as
here.

Then your V(1) or V(2) are rather V(1/2) and V(3/2) (and V(0) is
V(-1/2)..) Indeed, YADE does not give you the instantaneous velocity
value at time △t

To conclude with my feelings with respect to your (1)/(2)

(1) I do not see any other error outside the one necessarily introduced
by the finite difference approximation

(2) Yes if you want. More precisely it is the value one half time step
earlier (this "circled minus superscript" value).

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