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.dur...@inrae.fr
<mailto:jerome.dur...@inrae.fr>> 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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