X <#>LatexIt! 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 boundariesactually 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://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@lists.launchpad.net/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...@lists.launchpad.net> on
behalf of Bruno Chareyre <bruno.chare...@grenoble-inp.fr>
*Sent:* July-28-16 10:06 AM
*To:* yade-dev@lists.launchpad.net
*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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