yade-dev team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

Hi Vaclav,

why not trying to calculate the velocities at the right time? I remember I
was doing it and energy was conserved (without damping, either local or
global). We just need to shift them by adding acc*dt/2 (btw, we need to
_subtract_ this term in order to shift in the right way, as discussed with
Bruno on the list). It is worth a try. However, reducing the time step
should help, if we do not apply the shift.

Chiara
PS nice idea to track energies in this way


2010/11/13 Václav Šmilauer <eu@xxxxxxxx>

>
> I am not sure about the cause; two possible explanations come to mind (i)
> mid-step values of velocity vs. on-step accelerations etc. and (ii) without
> damping, many elastic collisions take place (their number increases if
> damping is small, as the system never goes to quasi-static state) and
> integration error accumulates (what contradicts this is that the precision
> would be increased with smaller dt, which is not the case, and also that the
> imprecision effects would cancel each other in average).
>
> Could someone have a look at the code and suggest something?
>
> Cheers, Vaclav
>
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