Cold flow across a hot solid

Numerical methods and mathematical models of Elmer
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kevinarden
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Cold flow across a hot solid

Post by kevinarden » 03 Apr 2019, 12:12

Solid initial at 227 and fluid initial at 20. Body has a radiating boundary at 227. Inlet has 0 degree fluid. The initial condition looks as expected.
initial.png
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After the flow starts the 0 degree fluid is entering the inlet. However a cold region grows over the solid, foes to -200 degrees. Heat is seen radiating from the solid on the right side.
flow_start.png
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I did not expect this cold region to form, should it be expected?
case.sif
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kevinarden
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Re: Cold flow across a hot solid

Post by kevinarden » 03 Apr 2019, 12:13

mesh.zip
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mzenker
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Re: Cold flow across a hot solid

Post by mzenker » 03 Apr 2019, 14:41

Hi,

AFAIK if radiation is involved all temperatures have to be in K.

HTH,
Matthias

kevinarden
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Re: Cold flow across a hot solid

Post by kevinarden » 04 Apr 2019, 00:02

Converted the temperatures to Kelvin, same result, there is a cooling area above the hot solid, prior to the cold flow reaching it.

dmitry
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Re: Cold flow across a hot solid

Post by dmitry » 04 Apr 2019, 10:21

I have met the same troubles. It is numerical instabilities near high temperature gradient.
You can look here:
viewtopic.php?f=3&t=4164&p=14705#p14705
Peter gave me some tips. In fact, only mesh refining near the walls was resultative.

dmitry
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Re: Cold flow across a hot solid

Post by dmitry » 04 Apr 2019, 10:27

PS: I do not tried to play with Initial guess.

kevinarden
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Re: Cold flow across a hot solid

Post by kevinarden » 04 Apr 2019, 11:27

Thanks, mesh refinement was my next step, and it resolved the problem.

Kevin

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