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On and Off of Reverse flow warning

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Old   December 22, 2011, 06:42
Default On and Off of Reverse flow warning
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I am trying to solve problem with internal heat generation. I got converged information from fluent when residuals was set 0.01 value. Then i decreased the residual to obtain more accurate results. To converge for the set residual i decreased the momentum URF value from 0.7 to 0.1.

Initially the residuals trend was nice. But then after continuity convergence of the order of 0.00001 i was getting REVERSE FLOW warning at fluent interface. After some iteration continuity residuals start increasing to 0.0001 or so. And with this my REVERSE FLOW warning disappear. But the warning comes again when continuity residuals decreases. And this trend continue.

I dont have a clue why this is happening. Any suggestion to overcome this problem or to understand this behaviour will be helpful for me.

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Old   December 24, 2011, 06:22
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where flow reverse is occurring. Can you attach the vector plots (from different views) at that boundary.

The possibilities/solution are:

1. It is normal with the outlet boundary with parallel flow. you need not to worry if solution is converged to required level.
2. Due to coarse mesh at the boundary the warning may come. This is again normal if convergence is obtained.
3. Due to close outflow/interface boundary. In case of interface boundary you cant do much, however in case of outflow the remedy is to place the outflow at further downstream.
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