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Old   February 23, 2011, 03:05
Unhappy residual oscillations
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hi im relatively new to cfx, and im trying to model a can combustor flow with a mixture of propane and butane as the fuel. im getting steady residual oscillations in the solver after a 100 hundred iterations. im using EDM, k-e for turbulence. can anyone tell me why this is happening - i've tried changing to physical timescale, increasing the timestep, decreasing it,but nothing is working. id be really grateful for any help. thanks.
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Old   February 23, 2011, 17:45
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http://www.cfd-online.com/Wiki/Ansys...gence_criteria
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Old   February 24, 2011, 14:43
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Did it converge without combustion?
What does the mesh quality report in the outfile say?
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Old   February 28, 2011, 02:34
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@ghorrocks, i ve read through that already.. and though the timescale alteration works for some curves, the others are still steadily in a straight line. is it possible i have to change my boundary conditions? i have converged similar models with the same BCs.
@joey: i havent tried running it without combustion. i will do that now and see.
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Old   February 28, 2011, 07:36
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it doesnt converge without combustion either - what does that mean?
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Old   February 28, 2011, 17:42
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and though the timescale alteration works for some curves
The page I referenced discusses a lot more than just the time scale. If the timescale does not work you have to consider the other approaches discussed there.
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Old   March 1, 2011, 15:25
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If it does not converge without combustion, something basic is wrong. Follow the recommendation from Glenn.
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