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Set sin function in my heat flux boundary condition

Topics: 3.5a, Heat Transfer

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Ehsan

Ehsan

March 18, 2010 6:27pm UTC

Set sin function in my heat flux boundary condition

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

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Ivar Kjelberg

Ivar Kjelberg
Moderator

March 18, 2010 9:01pm UTC in response to Ehsan

Re: Set sin function in my heat flux boundary condition

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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Rock Rockins

Rock Rockins

September 9, 2011 8:32pm UTC in response to Ivar Kjelberg

Re: Set sin function in my heat flux boundary condition

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

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Ivar Kjelberg

Ivar Kjelberg
Moderator

September 10, 2011 9:32am UTC in response to Rock Rockins

Re: Set sin function in my heat flux boundary condition

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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Rock Rockins

Rock Rockins

September 11, 2011 5:57pm UTC in response to Ivar Kjelberg

Re: Set sin function in my heat flux boundary condition

Thanks. It worked.

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