Wow you chose a challenging problem. Or did it chose you?
The convergence looks fine. If this was my final run I would continue to solve until the residuals "flatline", but for model development and debugging this is good enough.
I do not see a control at the end, usually a cone or something, that forces some of the stream back. Is this in your model? Also we do not see temperature here. But what causes the temperature to change. And how is that reflected in your model? There is a big something in the physics that seems to be missing.
Also I would review your turbulence model. I would recommend looking at what people typically use for hydrocyclones--these have similar high swirl properties.
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