On and Off of Reverse flow warning

prince_pahariaa · December 22, 2011, 05:42

Hii friends

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.

Thankss

Far · December 24, 2011, 05:22

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.

December 22, 2011, 05:42	On and Off of Reverse flow warning	#1
prince_pahariaa Member prince Join Date: Jun 2011 Posts: 56 Rep Power: 14	Hii friends 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. Thankss

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December 24, 2011, 05:22		#2
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	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.