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[Jerome Duriez <Jerome.Duriez@xxxxxxxxxxx>]

I hoped the "actually" would convey the "positive energy" meaning (like I would speak of a "true" acceleration for an increasing speed), but it seems it's not the case...


I still prefer "my" proposal but I would not oppose any further changes !



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Jerome Duriez, Research Associate

University of Calgary, Dpt of Civil Engineering

+1 403 220 7367


________________________________
From: Yade-dev <yade-dev-bounces+jerome.duriez=ucalgary.ca@xxxxxxxxxxxxxxxxxxx> on behalf of Bruno Chareyre <bruno.chareyre@xxxxxxxxxxxxxxx>
Sent: July-28-16 11:06 AM
To: yade-dev@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Yade-dev] TriaxialStressController.externalWork sign

XLatexIt! run report...

*** Found expression $u$
*** Found expression $T$
*** Found expression $ \int_{\partial \Omega} \boldmath T \cdot  \bm u ds$
Image was already generated



I don't think it makes much sense to speak of whether it is negative or positive.


"negativ when the boundaries actually provide energy to the sample", you mean when the boundaries actually provide a positive energy to the sample?

Since if it provides a negative energy then the function will return a positive value. ;)

I would suggest plain mathematical definition:

"Mechanical work associated to the boundary conditions, i.e. [$               \int_{\partial \Omega} \boldmath T \cdot  \bm u ds$]  with [$T$]  the surface traction and [$u$]  the displacement at the boundary."


There is no strong argument to multiply such a straight definition by -1 in my view.


Bruno



On 07/28/2016 06:33 PM, Jerome Duriez wrote:

Ok, I just proposed something:

https://github.com/yade/trunk/commit/6a9b6178ebade3c6d5ea6cbcdf439a9f20073648

[https://avatars1.githubusercontent.com/u/5427081?v=3&s=200]<https://github.com/yade/trunk/commit/6a9b6178ebade3c6d5ea6cbcdf439a9f20073648>

Doc clarification for TriaxialStressController.externalWork (http://w…; · yade/trunk@6a9b617<https://github.com/yade/trunk/commit/6a9b6178ebade3c6d5ea6cbcdf439a9f20073648>
github.com
…ww.mail-archive.com/yade-dev@xxxxxxxxxxxxxxxxxxx/msg12083.html<mailto:ww.mail-archive.com/yade-dev@xxxxxxxxxxxxxxxxxxx/msg12083.html>)




Thanks,


Jerome



--------------------------------------------------

Jerome Duriez, Research Associate

University of Calgary, Dpt of Civil Engineering

+1 403 220 7367


________________________________
From: Yade-dev <yade-dev-bounces+jerome.duriez=ucalgary.ca@xxxxxxxxxxxxxxxxxxx><mailto:yade-dev-bounces+jerome.duriez=ucalgary.ca@xxxxxxxxxxxxxxxxxxx> on behalf of Bruno Chareyre <bruno.chareyre@xxxxxxxxxxxxxxx><mailto:bruno.chareyre@xxxxxxxxxxxxxxx>
Sent: July-28-16 10:06 AM
To: yade-dev@xxxxxxxxxxxxxxxxxxx<mailto:yade-dev@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Yade-dev] TriaxialStressController.externalWork sign


Hi Jérôme,

Strictly speaking the doc is right: "Energy provided by boundaries" does not tell if the boundaries provide energy to the sample or to the outside.

I agree that it is probably more common to define "external work input" as an input to the sample, yet overall it remains a matter of taste.

I'm not for discussing/changing such sign conventions unless they are obviously wrong. There are probably tons of user scripts which would have to be adapted after such change (including mines), not a good thing. Instead, I would clarify the documentation without changing the code.

Bruno

On 07/27/2016 07:26 PM, Jerome Duriez wrote:

Hello,


I'm proposing to change the sign convention of TriaxialStressController.externalWork.


I would like it corresponds to the "Energy provided by boundaries" as the doc says, however it seems to me it's currently rather the energy provided to the boundaries (by the sample). Since we use the Force acting on the boundaries together with the boundaries velocities.


Agree to revert this sign ?


Jerome



--------------------------------------------------

Jerome Duriez, Research Associate

University of Calgary, Dpt of Civil Engineering

+1 403 220 7367



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