Convergence Criteria in FLUENT
Hello everyone
I am new to CFD. I am doing analysis of flow past circular cylinder in ANSYS 13. I created a mesh in ICEM CFD and I am currently doing mesh sensitivity study by refining mesh. I set the convergence criteria to 1e-06 as I am doing laminar flow. I am interested in cd values and I am monitoring cd too. Even after residuals meet convergence criteria, cd value is getting changed. I mean each cd value is repeating twice or thrice and decreasing to next value. If I leave it as such, each value is repeating as many as 10 times. When can I stop? Thank you |
If the change in Cd over iterations is higher than the expected variation then try reducing your relaxation factors
Regards Luke |
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You should observe the value up to fourth decimal place. I usually keep the convergence criteria up to 10e-12 for laminar flows, like you have, so that drag easily converge to required value.
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CL,CD and CM are global parameters. You should iterate until the drag converges up till third decimal place at least. If there are large oscillations in CD monitor then check your boundary conditions and the quality of your mesh.
Regards |
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Can I assume a converged solution if cd doesnot change over 10-12 iterations? |
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Also i have refined mesh 5 folds and it came upto 60 MB of mesh file. Is it normal? And it is taking lot of time fr each iteration. My computer does not have great processing speed. |
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