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Old   January 16, 2004, 12:24
Default nonsense Temp. values
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bogesz
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Hi all,

I'm running a trans. simulation: the initial Temp. is 266 C in a wall, near the wall water flows with the same temperature (pressure is 123 bar). At t=0 water enters at the inlet with a temp. of 166 C, and that's the transient. I have a solid domain for the wall, we want to investigate the heat conduction behavior of the wall. So the initial Temp. for both the fluid and solid domain is 266 C. The strange thing: after the start of the transient the global maximum value of the T starts rising until it reaches 278 C. It is hard to find the location of those "extreme T values", but for example it is quite easy to display tiny regions (only in the solid domain) with 267-268 C or so. But this is absolutely insane since there's only cooling down from the init. T value, no heat source in the problem. The calculation seems to be converged. I use cfx 5.5.1

any ideas?

thanks bog
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Old   January 16, 2004, 12:34
Default Re: nonsense Temp. values
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Johnson
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Hi Bog

I suspect the un-physical temperature regions in your solid region are near the solid-fluid interface. I also suspect you may be using a pure tet mesh. If this is the case, try using inflation on the solid-fluid interfaces - this should reduce the problem significantly.

Johnson
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Old   January 21, 2004, 09:19
Default Re: nonsense Temp. values
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bogesz
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thanks, but I actually used inflation, of course, in the fluid domain - on the fluid-solid interf. surface. I guess you were thinking about this.

Any other suggestions?

thanks bog
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Old   January 30, 2004, 14:30
Default Re: nonsense Temp. values
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Martin Bowers
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What discretization scheme are you using? Anything other than first order might allow an over / undershoot..
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Old   February 2, 2004, 08:29
Default Re: nonsense Temp. values
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bogesz
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hi Martin,

I tried both first order and second order high res. for the advection schemes and first order and second order backw. Euler for time discretisation. What do you mean over/undershoot? wich order may result in wich?

thanks

bog
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