Menu

Discussion Forum

New Discussion
Filtrer

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Set sin function in my heat flux boundary condition

Posted 18 mars 2010, 14:27 UTC−4 Heat Transfer & Phase Change Version 3.5a 4 Replies

Ehsan
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hello Guys,

I do not know how I can set a function in my boundary condition rather than a scalar. I need to define my wall's heat flux as a function of time which is almost like a sin function. I am sure the COMSOL should be able to handle that, but I do not know how!

Thank you

Ehsan
4 Replies Last Post 11 sept. 2011, 13:57 UTC−4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 18 mars 2010, 17:01 UTC−4
Hi

I would try to multiply the heat source value (amplitude) by a "*sin(2*pi*t)" factor.

But as "t" is only defined in "transient mode" you would get an error message if you switch to back to stationary, without supressing it again.

Good luck
Ivar
Hi I would try to multiply the heat source value (amplitude) by a "*sin(2*pi*t)" factor. But as "t" is only defined in "transient mode" you would get an error message if you switch to back to stationary, without supressing it again. Good luck Ivar
Rock Rockins
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 9 sept. 2011, 16:32 UTC−4
I am trying to change the external temperature as a sinusoidal function of time. The model is in transient mode, yet i still get the unit error when i simply plug in ext. temp = 280*Sin(t).
I also tried to change it from global expression, but still i get the unit mismatch error. How else can i change the external temperature as a sine function?

Appreciate any help. Thanks
I am trying to change the external temperature as a sinusoidal function of time. The model is in transient mode, yet i still get the unit error when i simply plug in ext. temp = 280*Sin(t). I also tried to change it from global expression, but still i get the unit mismatch error. How else can i change the external temperature as a sine function? Appreciate any help. Thanks
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 10 sept. 2011, 05:32 UTC−4
Hi

the unit mishmthc is that "t" has units [s] and the operator sin() wants unitless values:

hence you shoud either write a[m]=a0[m]*sin(2*pi*f[Hz]*t[s]) without necessarily all units if already defined
or just sin(t[1/s]) to be unitless

--
Good luck
Ivar
Hi the unit mishmthc is that "t" has units [s] and the operator sin() wants unitless values: hence you shoud either write a[m]=a0[m]*sin(2*pi*f[Hz]*t[s]) without necessarily all units if already defined or just sin(t[1/s]) to be unitless -- Good luck Ivar
Rock Rockins
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 11 sept. 2011, 13:57 UTC−4
Thanks. It worked.
Thanks. It worked.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content