After some tests I would like your opinion on my preliminary conclusion ideas.
I did several simulations with different flows, from initial speed v0, to v0 x10.

In several cases simulation seems to converge and stabilizes with residuals 1E4 or less, but blows up in just some steps., can the solution be used before the blow up? If the residuals are low I dont´t see why not…

I found more difficult to achieve convergence, or just low residuals, with increasing flow, why could be the reason?

I found from some suggestions, googling, and trial/error this very basic setup to get stabilized convergence, or at least to get to low residuals (1E4 or less), although with enough steps, (1000 or so) a lot of times seems to suddenly (in just 45 steps) blow up
1 Reduce relaxing factors some 2030%
2 Change default solvers to pressure GAMG, rest (Smoothsolver)
3 Reduce relaxing factors some additional 2030%
4 Change default solvers to all (Smoothsolver), slows very much the convergence
I read regarding the inner working of the SIMPLE algorithm but, Is there any additional info regarding the solvers and their detailed parameter setup, in order to improve convergence or selecting the most suitable for any kind of problem?
Thanks for your comments