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Unknown variables while defining expressions.

Posted Jan 27, 2011, 1:39 a.m. EST Version 4.1 5 Replies

Deepak
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I have defined the expressions in version 3.4, but I am not able to define same expressions in version 4.1.The expressions are as follows:
Q11 alpha_smsld*(T-T0)[K]*(E11[N/m^2]+E12[N/m^2]+E13[N/m^2])
Q12 alpha_smsld*(T-T0)[K]*(E21[N/m^2]+E22[N/m^2]+E23[N/m^2])
Q13 alpha_smsld*(T-T0)[K]*(E31[N/m^2]+E32[N/m^2]+E33[N/m^2])
Q1 Q11*uxt+Q12*vyt+Q13*wzt
Sel1 alpha_smsld*(E11[N/m^2]*(ux-alpha_smsld*(T-T0))+E12[N/m^2]*vy+E13[N/m^2]*wz)
Sel2 alpha_smsld*(E22[N/m^2]*(vy-alpha_smsld*(T-T0))+E12[N/m^2]*ux+E23[N/m^2]*wz)
Sel3 alpha_smsld*(E33[N/m^2]*(wz-alpha_smsld*(T-T0))+E13[N/m^2]*vy+E23[N/m^2]*wx)
Sel Sel1+Sel2+Sel3
S rho_smsld*C_htgh*log(T/T0[k])+Sel
Q2 T*pdiff(S,t)

Please kindly help me in defining these equations in version 4.1.

How to generate report in comsol v 4.1.
5 Replies Last Post Jan 28, 2011, 1:25 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 Jan 27, 2011, 3:49 a.m. EST
Hi

there are many changes in v4, I spent also some time to get used to it.

first of all the "report" feature as per v3.5 is not yet implemented, you can generate plots, and save the generation such that its done in one go also in 4.1, it must be defined once manually (right click on the plot nodes to see all options)

for the formulas, you need to catch the new way, no longer suffix "_smsld" but prefix "solid." for all variables. Then in v4 and Structural, the "Deformed frame" is by default "on" this means that you have a different material and spatial (deformed) frames activ.

In 3.5 the "deformed frame" was off and all frames were referred to as x,y,z (lowercase). In v4 the spatial (deformed) frame is "on" and uses the lowercase x,y,z, while the material frame and the mesh has the uppercase X,Y,Z hence you need to think in which frame you are for your formulas, and often v3.5 lowercase x,y,z (derivatives) become X,Y,Z uppercase.

Its the old story of Euler or Lagrangian reference frame issue (more common to the fluidics)

--
Good luck
Ivar
Hi there are many changes in v4, I spent also some time to get used to it. first of all the "report" feature as per v3.5 is not yet implemented, you can generate plots, and save the generation such that its done in one go also in 4.1, it must be defined once manually (right click on the plot nodes to see all options) for the formulas, you need to catch the new way, no longer suffix "_smsld" but prefix "solid." for all variables. Then in v4 and Structural, the "Deformed frame" is by default "on" this means that you have a different material and spatial (deformed) frames activ. In 3.5 the "deformed frame" was off and all frames were referred to as x,y,z (lowercase). In v4 the spatial (deformed) frame is "on" and uses the lowercase x,y,z, while the material frame and the mesh has the uppercase X,Y,Z hence you need to think in which frame you are for your formulas, and often v3.5 lowercase x,y,z (derivatives) become X,Y,Z uppercase. Its the old story of Euler or Lagrangian reference frame issue (more common to the fluidics) -- Good luck Ivar
Deepak
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Posted: 1 decade ago Jan 27, 2011, 5:25 a.m. EST
Thanks for suggestions. I am not able to write the last expression in comsol v 4.1. I have to do partial differentiation of entropy S w.r.to time t.Can you suggest me expression?
Regards!!

Deepak
Thanks for suggestions. I am not able to write the last expression in comsol v 4.1. I have to do partial differentiation of entropy S w.r.to time t.Can you suggest me expression? Regards!! Deepak
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 27, 2011, 11:00 a.m. EST
Hi

if you cannot find any any internal name for the entropy derivative, you might get away with a d(S,t) the differentiator operator d(,) check the doc

--
Good luck
Ivar
Hi if you cannot find any any internal name for the entropy derivative, you might get away with a d(S,t) the differentiator operator d(,) check the doc -- Good luck Ivar
Deepak
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Posted: 1 decade ago Jan 27, 2011, 1:22 p.m. EST
Thanks again Ivar...I got the differential operator by exploring the documentation.partial differential can be written as pd(S,t) for my case.


Regards!!

Deepak
Thanks again Ivar...I got the differential operator by exploring the documentation.partial differential can be written as pd(S,t) for my case. Regards!! Deepak
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 28, 2011, 1:25 a.m. EST
Hi

Yes correct, I had forgotten to add "pd(,)" to the list of potential operator, if it not d(,) its pd(,) ;)

--
Good luck
Ivar
Hi Yes correct, I had forgotten to add "pd(,)" to the list of potential operator, if it not d(,) its pd(,) ;) -- Good luck Ivar

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