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Convergence criteria via mass flow rate surface monotor

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Old   November 22, 2019, 06:01
Default Convergence criteria via mass flow rate surface monotor
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Azeem
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Hello!
I am trying to simulate airflow inside ball bearing in Fluent. As in previous attempts, the continuity won't converge so I decided to use a surface monitor for mass flow rate on pressure outlet of the case after reading some articles from the internet. Now, in 10000 iterations case, I can see that the surface monitor started to fluctuate between similar values after maybe 3000 iterations.
1. I am not sure what should be the criteria for me to decide the convergence of the case based on this surface monitor. (I read somewhere that if the net difference b/w mass flow rate of inlet and outlet is less than 0.2% the case is considered to be converged).
2. In my case this difference b/w the mass flow rate of inlet and outlet is in 0.7-0.9% range.
I am not sure myself about what I am trying to ask so please excuse my lack of awareness :P
any guidance and suggestions will be highly appreciated, Thank you and please take a look at the attached pictures as well.
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Old   November 22, 2019, 11:26
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Lucky Tran
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Convergence is one thing. Accuracy, balances, and making any physical sense is another matter.

I would tentatively agree that it is converged after ~3000 iterations.

So now you should check if your results make sense and judge their quality. It's not really a question of whether it is converged or not anymore. It is. If you keep iterating until 1 million iterations, probably you will get the exact same result. That's what convergence means. If you don't like your results, you can change, modify, or fix some things.
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Old   November 24, 2019, 01:03
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Thank you for your response. Yes I was wrong to pursue the traditional convergence for this matter i.e, to get the pre-defined values of residuals. Anyway, I have analyzed the results and they make sense as well as provide me with the parameters which I am looking for.
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convergence, fluent, mass flow rate, single phase flow, surface monitor

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