hi,

what if the turbulent viscosity warning message persists until convergence but it's limited to few cells? is the solution still valid? would you suggest to adapt the grid cells where the turbulent viscosity is high? Thanks

I would say that it's a problem, even if limited to a few cells. The warning only appears when the turbulent viscosity hits unrealistic levels, so even cells that do not trigger the warning are likely to have overpredicted turbulent viscosity.

When you say "until convergence", is this from FLUENT's convergence criteria? If so, turn those off and continue to run the simulation until the residual history is flat and low for all variables. You will probably find if you examine the residual history, your turbulence residuals are still dropping and will be for some time yet (i.e., your solution is not actually converged yet).