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K-E residual fluctuation in combustor analysis

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Old   March 22, 2013, 09:17
Default K-E residual fluctuation in combustor analysis
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Case details
# Tet mesh with 0.27 quality in ICEM CFD
# No interfaces
# combustor domain + exit domain
# Solving mass+momentum+energy+combustion equations, SIMPLE algorithm

K-E residuals are fluctuating after changing from first order to second order (after 500 iteration)in pure tet-mesh CFD domain. K-E residuals are fluctuating even after 5000 iterations

Max residuals are only at a location with few elements connected to it. There elements are fine and above 0.27 mesh quality.
I used the same mesh + same fluent setup for different exit domain, there residuals are fine and solution is converging .The difference between the geometries are very minimal 0.030inch to 0.050 inch change in exit length. Remaining all are same.

Can anyone help me to find the root cause ?
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Old   March 23, 2013, 04:27
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Sijal Ahmed Memon (turboenginner@gmail.com)
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Why Simple algorithm?
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Old   March 23, 2013, 06:07
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Not SIMPLE , it is SIMPLEC . But no specific reason. Earlier analysis I tried with coupled algorithm but i found this SIMPLEC method shows faster convergence.
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