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Laminar Stiff reacting flow won't converge

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Old   May 26, 2010, 12:26
Default Laminar Stiff reacting flow won't converge
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Hi all--
I am new to this CFD forum. I am currently working on a model that has a compressible fluid in laminar flow with a stiff reaction network. The flow has several stagnant or mixing regions in it. I am trying to solve this several ways.
The first was to approach it like in the Fluent manual and initialize a cold flow then add in the reactions. The second way was to use the unsteady coupled solver for pressure and reduce the Courant number to 100. The time step I used was 0.001 sec.

The mesh I have in the channel with the fluid is structured and I have 14 nodes in the vertical direction. I have not messed with the AMG settings but am not ad versed to it. Just got to figure out what makes sense.

The problem is I can't get the continuity residual below 0.1 even with no reactions. When I add the reaction network the problem takes more than a week to solve and the residuals for some of the species are not that great.

I have solved the model in a simple PFR and know the chemistry is correct.

any help on solver settings, AMG setting or different ways to tackle this would be awesome!
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Old   March 13, 2012, 20:13
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Any success on how to converge the reacting flow, I appreciate your suggestions.

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compressible, laminar flow, reacting flow, stiff

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