yade-dev team mailing list archive

[Jerome Duriez <jerome.duriez@xxxxxxxx>]

Thanks for feedback, what about just a change in name: gravWork -> 
gravPotential ?

There would be no more doubts whether it is work by gravity or work 
against gravity ; and decrease of that quantity during a fall would seem 
more logical to me (and others ?)

I agree otherwise with your general remarks about O.energy, but since 
it's there (we won't remove it anyway, will we ?) I think it could be 
worth to make such a small improvement.

Jérôme


------
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On 28/04/2020 16:27, Bruno Chareyre wrote:
> Hi Jérôme,
> I feel like it is a question of perspective, and undecidable overall.
> Is it work by gravity or work against gravity? You can find the two 
> meanings easily. It's still a work in both cases.
>
> OTOH it seems these energies are underdocumented overall. I did not find 
> a list of available energies anywhere in the doc.
> I must say trackEnergy=True is slow. It computes many un-needed things 
> (gravitational work is a good example, why should we increment 
> G-=g*vel*dt at every iteration while we can get at any point in time 
> -g*pos? same issue with elastic work).
> In current design I would not recommend it although it is elegant and 
> handy for quick tests.
> Cheers
> Bruno
> So
>
> Bruno
>
> On Mon, 20 Apr 2020 at 16:13, Jerome Duriez <jerome.duriez@xxxxxxxx 
> <mailto:jerome.duriez@xxxxxxxx>> wrote:
>
>     I now think the most logical would be to keep this expression with a
>     minus sign [*], but rename 'gravWork' into 'gravPotential' (like we
>     have
>     'elastPotential').
>
>     It would reconcile for me the name with the coded expression, and be
>     more logical with the existence of O.energy.total() function (which
>     sums
>     all terms in O.energy and certainly is expected to be constant)
>
>
>     Thoughts ?
>
>     [*]
>     https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/NewtonIntegrator.cpp#L85
>
>     ------
>     Chargé de Recherche / Research Associate
>     Inrae, RECOVER
>     3275 route Cezanne – CS 40061 13182 Aix-en-Provence Cedex 5 FRANCE
>     +33 (0)4 42 66 99 21
>     https://www6.paca.inrae.fr/recover/membres-du-laboratoire/pages-personnelles/jerome-duriez
>
>     On 20/04/2020 10:25, Jerome Duriez wrote:
>      > Hi,
>      >
>      > Is there a consensus (outside myself) for the extra minus sign in
>      > O.energy['gravWork'], computed in NewtonIntegrator at [*].
>      >
>      > It seems that code line was initially introduced by Vaclav in
>      > GravityEngine in commit [**] (and made finally its way into
>      > NewtonIntegrator).
>      >
>      > As far as I'm concerned, I can not make sense of the comment
>     justifying
>      > that sign, just above [*], neither of a consequent negative power of
>      > weight during some free fall.
>      >
>      >
>      > Jérôme
>      >
>      >
>      > [*]
>      >
>     https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/NewtonIntegrator.cpp#L85
>
>      >
>      >
>      > [**]
>      >
>     https://gitlab.com/yade-dev/trunk/-/commit/d41480acf2ad616268c9ed562b625952c87c98a5,
>
>      > see also corresponding file from that time at
>      >
>     https://gitlab.com/yade-dev/trunk/-/blob/d41480acf2ad616268c9ed562b625952c87c98a5/pkg/common/GravityEngines.cpp#L33
>
>      >
>      > ------
>      > Chargé de Recherche / Research Associate
>      > Inrae, RECOVER
>      > 3275 route Cezanne – CS 40061 13182 Aix-en-Provence Cedex 5 FRANCE
>      > +33 (0)4 42 66 99 21
>      >
>     https://www6.paca.inrae.fr/recover/membres-du-laboratoire/pages-personnelles/jerome-duriez
>
>      >
>
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> --
> --
> _______________
> Bruno Chareyre
> Associate Professor
> ENSE³ - Grenoble INP
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