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boussinesq approximation when temperature difference is large

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Old   June 25, 2019, 00:11
Default boussinesq approximation when temperature difference is large
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HakminLee
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I'm studying on the natural convection of spent fuel in the dry storage system.

I understand that boussinesq approximation can be used only when the temperature difference is small.

If the temperature range is 300K-500K for example, is it right to simply use an incompressible ideagl gas law that uses the p=rho*R*T law?

Or can i just use the boussinesq approximation?

i don't know about these.


Thank your reply.
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Old   June 25, 2019, 12:38
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Erik
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That temperature range is too large for Boussinesq. I've heard 10% density difference maximum. Ideal gas is not incompressible, it is definitely compressible, and using that for density would be much more appropriate.
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Old   June 25, 2019, 21:20
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Quote:
Originally Posted by evcelica View Post
That temperature range is too large for Boussinesq. I've heard 10% density difference maximum. Ideal gas is not incompressible, it is definitely compressible, and using that for density would be much more appropriate.
Thankyou so much!
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Old   September 15, 2020, 16:07
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Quote:
Originally Posted by evcelica View Post
That temperature range is too large for Boussinesq. I've heard 10% density difference maximum. Ideal gas is not incompressible, it is definitely compressible, and using that for density would be much more appropriate.
Hi evcelica,
I have a doubt regarding coefficient of thermal expansion which we use in boussinesq approximation.
I am doing simulation for natural convection for a pcb in an enclosure. the freestream temp is 322K. i read bousinesq approximation is valid iff
beta * (T-T_ref) <0.05. in this for beta what should I consider. my fluid is air and as its an ideal gas beta = 1/T. so here what temperature should I use.

Thanks for the help
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