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Problem about Joule heating and thermal expansion

Posted 22 set 2012, 10:22 GMT-4 Heat Transfer & Phase Change, Structural Mechanics Version 4.2, Version 4.3 12 Replies

James
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Hi

I want to inject ac current (amplitude is fixed) to a silicon beam and hope to see maximum expansion when the ac frequency is at half of the mechanical resonant frequency of the beam. I tried using "Joule heating and thermal expansion" physics and frequency domain solver in Comsol 4.2 but the result is the same to the case where no current is applied. Reasonable result can be obtained when using stationary solver. Does anyone know how to solve this? Thanks.
12 Replies Last Post 11 giu 2013, 16:21 GMT-4
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 23 set 2012, 00:55 GMT-4
You should try to solve this as a transient problem instead.
You should try to solve this as a transient problem instead.
James
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Posted: 1 decade ago 23 set 2012, 03:48 GMT-4

You should try to solve this as a transient problem instead.


OK. It seems I have no other options. Thanks.
[QUOTE] You should try to solve this as a transient problem instead. [/QUOTE] OK. It seems I have no other options. Thanks.
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 23 set 2012, 23:55 GMT-4
The frequency domain study assumes a single frequency content and the Joule heating effect is a quadratic function of the current. That results in the frequencies for the temperature and displacement fields to be different from that of the electric field. That’s why I believe you need the transient solver.
The frequency domain study assumes a single frequency content and the Joule heating effect is a quadratic function of the current. That results in the frequencies for the temperature and displacement fields to be different from that of the electric field. That’s why I believe you need the transient solver.
James
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Posted: 1 decade ago 24 set 2012, 09:36 GMT-4

The frequency domain study assumes a single frequency content and the Joule heating effect is a quadratic function of the current. That results in the frequencies for the temperature and displacement fields to be different from that of the electric field. That’s why I believe you need the transient solver.


Thank you for your explanation. I think I will try transient solver and set frequency to a parameter. Then I can sweep this parameter to get the frequency response of the devic.
[QUOTE] The frequency domain study assumes a single frequency content and the Joule heating effect is a quadratic function of the current. That results in the frequencies for the temperature and displacement fields to be different from that of the electric field. That’s why I believe you need the transient solver. [/QUOTE] Thank you for your explanation. I think I will try transient solver and set frequency to a parameter. Then I can sweep this parameter to get the frequency response of the devic.
James
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Posted: 1 decade ago 25 set 2012, 20:27 GMT-4

The frequency domain study assumes a single frequency content and the Joule heating effect is a quadratic function of the current. That results in the frequencies for the temperature and displacement fields to be different from that of the electric field. That’s why I believe you need the transient solver.


Hi

I tried transient solver on the Joule heating and thermal expansion physics in COMSOL4.2. There is always a error "Failed to evaluate the variable mod1.tem.DZ". But the problem is gone when I used just joule heating physics. Is there anything I need to notice when transient solver is used on the Joule heating and thermal expansion physics? Thanks.

James
[QUOTE] The frequency domain study assumes a single frequency content and the Joule heating effect is a quadratic function of the current. That results in the frequencies for the temperature and displacement fields to be different from that of the electric field. That’s why I believe you need the transient solver. [/QUOTE] Hi I tried transient solver on the Joule heating and thermal expansion physics in COMSOL4.2. There is always a error "Failed to evaluate the variable mod1.tem.DZ". But the problem is gone when I used just joule heating physics. Is there anything I need to notice when transient solver is used on the Joule heating and thermal expansion physics? Thanks. James
Kai Hwang
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Posted: 1 decade ago 3 nov 2012, 07:56 GMT-4
Hi,

I am new to COMSOL,I habe same frequency domain problem about Joule heating and thermal expansion with you ,could you tell me, how can i set "transient solver " in COMSOL4.3?


thanks

Kai
Hi, I am new to COMSOL,I habe same frequency domain problem about Joule heating and thermal expansion with you ,could you tell me, how can i set "transient solver " in COMSOL4.3? thanks Kai
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 3 nov 2012, 10:08 GMT-4
Hi

exactly which "physics are you using? "TEM" ? and are you looking for a transient time pulse change or an continuous AC sin(2*pi*f*t) type load, in which case you should also consider the frequency domain solver cases.

Have you searched the model library and model gallerie on the web for typical exmples ?

--
Good luck
Ivar
Hi exactly which "physics are you using? "TEM" ? and are you looking for a transient time pulse change or an continuous AC sin(2*pi*f*t) type load, in which case you should also consider the frequency domain solver cases. Have you searched the model library and model gallerie on the web for typical exmples ? -- Good luck Ivar
Kai Hwang
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Posted: 1 decade ago 3 nov 2012, 10:27 GMT-4
Hi,
Thanks for your reply,i am using physics "Joule heating and thermal expansion" ,want to connect ac voltage with variational frequency to a silicon beam ,hope to find resonance frequency und maximum displacement of beam.
but with "Joule heating and thermal expansion" physics and frequency domain solver in COMSOL get I no result ,und Number of degrees of freedom solved for 0.

Kai
Hi, Thanks for your reply,i am using physics "Joule heating and thermal expansion" ,want to connect ac voltage with variational frequency to a silicon beam ,hope to find resonance frequency und maximum displacement of beam. but with "Joule heating and thermal expansion" physics and frequency domain solver in COMSOL get I no result ,und Number of degrees of freedom solved for 0. Kai
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 3 nov 2012, 18:03 GMT-4
Hi

that is because TEM is not set up for standard " frequency domain " solving (it's not any option when you add TEM as new physics), you have "only" Frequency Domain, Perturbation" check the doc, probably because HT equations are not wave equations

--
Good luck
Ivar
Hi that is because TEM is not set up for standard " frequency domain " solving (it's not any option when you add TEM as new physics), you have "only" Frequency Domain, Perturbation" check the doc, probably because HT equations are not wave equations -- Good luck Ivar
Kai Hwang
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Posted: 1 decade ago 5 nov 2012, 02:31 GMT-5
Hi
thanks for your answer,according to your suggestion try i "Frequency Domain, Perturbation",but it does not support "TEM".

Kai

Hi thanks for your answer,according to your suggestion try i "Frequency Domain, Perturbation",but it does not support "TEM". Kai
Vidyaa V
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Posted: 1 decade ago 14 mar 2013, 02:21 GMT-4
Hi,
I have similar problem. I am using Joule heating and thermal expansion physic and i am trying to do transient analysis(time dependant) analysis to obtain the temperature variation and the displacements in an electrothermal gripper. I am getting the error, failed to evaluvate variable.mod1.tem.DX, for the geometry in all domains. How to solve this error? kindly help me.

Thanks and regards
vidyaa
Hi, I have similar problem. I am using Joule heating and thermal expansion physic and i am trying to do transient analysis(time dependant) analysis to obtain the temperature variation and the displacements in an electrothermal gripper. I am getting the error, failed to evaluvate variable.mod1.tem.DX, for the geometry in all domains. How to solve this error? kindly help me. Thanks and regards vidyaa
Anosh Daruwalla
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Posted: 1 decade ago 11 giu 2013, 16:21 GMT-4
Did anyone solve this finally? I did this using the transient solver, but it takes too long to solve since I have too many time steps to solve for. I would greatly appreciate it if anyone did manage to do a harmonic analysis of joule heating, perhaps even using the equations module to form one's own equations rather than the precooked modules.
Did anyone solve this finally? I did this using the transient solver, but it takes too long to solve since I have too many time steps to solve for. I would greatly appreciate it if anyone did manage to do a harmonic analysis of joule heating, perhaps even using the equations module to form one's own equations rather than the precooked modules.

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