Laminar Stiff reacting flow won't converge
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!
Any success on how to converge the reacting flow, I appreciate your suggestions.
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