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HUGE change in results between opening and inlet

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Old   October 30, 2013, 11:45
Default HUGE change in results between opening and inlet
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Greg
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I'm struggling to understand the difference between an opening and inlet boundary condition. I ran my model of a tube transporting hot gas and cooled by convection of the surrounding air domain. I tried changing one wall of the surrounding air domain from opening to inlet (in both cases I set the boundary temp and pressure the same). I get a really big difference in the resulting temperature drop of the hot gas. Can anyone explain why, and which boundary condition is more appropriate?


Thanks,
Greg
Attached Images
File Type: jpg internal_fins_exh_temp_amb_opening.jpg (45.3 KB, 9 views)
File Type: jpg internal_fins_exh_temp_amb_inlet.jpg (41.4 KB, 9 views)
File Type: jpg opening_setup.jpg (46.5 KB, 8 views)
File Type: jpg inlet_setup.jpg (42.0 KB, 7 views)

Last edited by gwheeler; October 30, 2013 at 12:00. Reason: clarified slightly
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Old   October 30, 2013, 12:23
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even if it could be unreliable, have you tried static pressure on both cases as the BC?
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Old   October 30, 2013, 12:49
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Yes, no significant difference in either case when I specify static pressure. Still a huge difference between the two cases.
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Old   October 30, 2013, 13:22
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you could try to extend both ends of BCs (inlet, outlet)
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Old   October 30, 2013, 17:58
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Have you looked at the velocity vectors? I bet the flow is totally different in the two cases.
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