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Old   February 13, 2020, 00:57
Default need help convergence problem
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hi all , i need help with my model . the problem is with residuals in continuity dosent reach 10-3 and by monitoring the results doesn't reach constant value .
solver setting :
simplec , second order scheme for pressure and quick scheme for all other convection parameters.
the model and mesh and results in photos
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File Type: png residuals.png (9.0 KB, 7 views)
File Type: png results.png (23.7 KB, 6 views)
File Type: png settings.png (10.7 KB, 6 views)
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Old   February 13, 2020, 04:24
Default Use Coupled
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Mahmoud, for such a system, prefer using Coupled with pseudo-transient. Furthermore, no need to use QUICK. Difference between QUICK and second-order would be too small.
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Old   February 14, 2020, 05:45
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Quote:
Originally Posted by vinerm View Post
Mahmoud, for such a system, prefer using Coupled with pseudo-transient. Furthermore, no need to use QUICK. Difference between QUICK and second-order would be too small.
THANKS vinerm , its works but the coupled solver induced back flow(rise the error) even with down steram flow 2.5times the model length .so what is your recommendations for that problem.
great thanks for your help
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Old   February 14, 2020, 06:05
Default Flow reversal
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In some cases, flow reversal is realistic, such as, for cases with obstructions very close to the outlet. Otherwise, you should observe that as the iterations proceed, the number of faces having flow reversal reduces. In case it is not reducing then the obstruction is too close to the outlet and you should extend the domain; recommended is 6 times the hydraulic diameter away from any obstruction. If reversal exists only on a couple of faces, you can ignore that. Extension would not be justified.
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