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Set sin function in my heat flux boundary condition

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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 2011年9月11日 GMT-4 13:57
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2010年3月18日 GMT-4 17:01
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

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Posted: 1 decade ago 2011年9月9日 GMT-4 16:32
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)

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Posted: 1 decade ago 2011年9月10日 GMT-4 05:32
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

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Posted: 1 decade ago 2011年9月11日 GMT-4 13:57
Thanks. It worked.
Thanks. It worked.

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