I am working on mixing flow problem, where two separate flows mixes at a junction, one at high temperature (super heated) and other at lower temperature (saturated), both at same pressure. They mix to common outlet at moderate temperature. The fluid considered is carbon dioxide. I am using real gas model in fluent.
But the solution is not converging even after 10k iterations ( no divergence issue), even though the mass flow rates are stabilized. My presumption is that density variation is causing this, because when I turn it to ideal gas it works.
How can I deal with such problems?
It may be that in the real world such a mechanism would not converge. In other words you have a chaotic or a non-linear system. The first thing to investigate would be whether it is cycling, and determine what is its period.
There is a description of chaotic systems here http://en.wikipedia.org/wiki/Chaotic_systems but your system may be just oscillating, which is the simplest form of chaos, rather than entering a full blooded strange attractor.
The Wikipedia entry has many references and further reading at the end.
Rajesh, thanks for letting me know. It was only a guess, although based on a similar experience.
Rajesh, What did you do that made it work? I have had similar problems.
Hi David,
I am suggesting that you cannot get it "to work." The configuration you have is unstable, and in the real world it would oscillate or enter a strange attractor. It is similar to the Predator-Prey model described here: http://www.tp.umu.se/ModSim/files/PP-lect.pdf and elsewhere.
Google chaos theory , Lotka–Volterra equation, or the Logistic equation.
"The Lotka–Volterra predator–prey model was initially proposed by Alfred J. Lotka in the theory of autocatalytic chemical reactions in 1910.[4][5]" https://en.wikipedia.org/wiki/Lotka%E2%80%93Volterra_equations#History
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