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Problem with differentiation operator ( zero result )

Posted Feb 16, 2012, 4:49 a.m. EST MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Parameters, Variables, & Functions, Results & Visualization Version 4.2 2 Replies

Mousavi Hasan
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Hello to all

I set up a "tem" physics interface ( joulheating and thermal expansion) and want to get a spatial derivative from some variable such as stress , pressure and temperature. I used Tx , ux , d(u,x) , d(tem.p,x) , etc. but it gives zero everywhere in the domains as result.

I've read the forum and changed the shape function to cubic but the results doesn't change.

Also, I have added a PDE in the form of u2 = d(T,x) but the given results is obviously meaning less and wrong and doesn't match with the temperature gradient which is a predefined result for "tem" !

I don't know what else I can do.
2 Replies Last Post Feb 18, 2012, 6:57 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 17, 2012, 3:06 p.m. EST
Hi

if you are in V4.2a, I believe it's TX the derivative w.r.t. the material frame, (and not Tx the derivative of the spatial frame)
the same for uX and uXX, and for d(d(tem.p,X),Y), use upper case X,Y,Z,R

At least that works for me in V4.2a, even nicer & smoother with cubic or quartic shape functions

--
Good luck
Ivar
Hi if you are in V4.2a, I believe it's TX the derivative w.r.t. the material frame, (and not Tx the derivative of the spatial frame) the same for uX and uXX, and for d(d(tem.p,X),Y), use upper case X,Y,Z,R At least that works for me in V4.2a, even nicer & smoother with cubic or quartic shape functions -- Good luck Ivar
Mousavi Hasan
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Posted: 1 decade ago Feb 18, 2012, 6:57 a.m. EST
Dear Ivar
Thank you very much, it worked. God bless you :)

Kind regards
Dear Ivar Thank you very much, it worked. God bless you :) Kind regards

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