K-E residual fluctuation in combustor analysis

jthiakz · March 22, 2013, 08:17

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 ?

Far · March 23, 2013, 03:27

Why Simple algorithm?

jthiakz · March 23, 2013, 05:07

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.

March 22, 2013, 08:17	K-E residual fluctuation in combustor analysis	#1
jthiakz Member Thiagu Join Date: Oct 2012 Location: India Posts: 60 Rep Power: 13	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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March 23, 2013, 03:27		#2
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	Why Simple algorithm?

March 23, 2013, 05:07		#3
jthiakz Member Thiagu Join Date: Oct 2012 Location: India Posts: 60 Rep Power: 13	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.