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Old   November 19, 2008, 11:32
Default About Newton iteration
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Lixian
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I am a beginner of CFX. I am simulating a Hydrogen/Air reaction in a round micro chamber with 250 micro meters in height and 8 millimeters in diameter. The mesh size is 20 micrometers, and the time step is 2E-6. I can't get convergence with the following error. Can you help me to find the reason? Many thanks! "Newtons method failed to converge in 100 iterations. This occurred while computing the following variable: | Variable Name:Total temperature Location Name : Default Domain | Mesh location : VERTICES | Tolerance : 1.0000E-02 | The Newton iteration was diverging. The solver will continue with the variable field as it was on the final iteration. If this situation continues you might try decreasing the Netwon iteration under relaxation factor. This can be changed by setting one of the following parameters: Temperature : "Constitutive Relation Under Relaxation" Pressure : "Newton Pressure Under Relaxation" for your mixture using the definition file editor. "

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Old   November 20, 2008, 12:10
Default Re: About Newton iteration
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John S.
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Fairly common error. In my experience this is usually caused by bad grid. When I encounter this error I might try changing my BCs a little but usually I just repent - remesh - rerun.
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Old   November 20, 2008, 22:46
Default Re: About Newton iteration
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frank
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I think the main reason is your non-physical boundary settings. So i strongly suggest your review your physical model.
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Old   November 27, 2008, 08:57
Default Re: About Newton iteration
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Lixian
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Dear John and Frank, thank you for your suggestions. I tried both remesh and rerun, and I changed the boundary settings, but I still can not get convergence. It always said "the newtons method can not converge in 100 iterations". If I delete all the reactions and try only with steady flow, it can run completely. I am really worried and anxious about the problem which I have struggling for a whole week. Can I have a moment to discuss with you? my MSN is xulixian_jerry@hotmail.com, you can add me, I am always online. I am really appreciate
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