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Old   December 13, 2002, 04:24
Default Convergence problem
Atul T. Shinde
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Dear all, I am working with rotating flows. First I used the "simple" discretization scheme and run the model for around 1500 iterations. For momentum, I used First order. It went smoothly. When I changed it to the second order for momentum and Presto for PRessure, after around 1800 iterations, the solution started to diverge. Also I tried with the multiple reference frame. I could avoid the divergence till some more iterations but that as well started to diverge. CAn anybosy help me in this regard? Thanks
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Old   December 13, 2002, 15:38
Default Re: Convergence problem
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try using other schemes like body force wieghted under pressure is always good for rotating flows.
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Old   December 20, 2002, 01:35
Default Re: Convergence problem
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This site says:

FLUENT Defects ID: 12318

Summary: PRESTO scheme for pressure interpolation when used in some cases with the FIX option for velocity can cause divergence.

Product Name: Fluent6 Component Name: Boundary Conditions Version Found: 6.0.13 Version Fixed: 6.0.13 Reported date: 11/16/01 11:53:26 AM

Description: The FIX option with PRESTO interpolation scheme leads to the divergence of the case. files are in the appropriate folder. boite_standard.cas.gz boite_standard.dat.gz --> convergence with standard interpolation scheme. boite_bfw.cas.gz boite_bfw.dat.gz --> convergence with body force weighted interpolation scheme. boite_PRESTO.cas.gz boite_PRESTO.dat.gz --> divergence with PRESTO interpolation scheme. source.c --> udf who impose the definition of the fix velocity.
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