Hi all...

I've some convergence problem while using SSG RSM. The size of the near wall elements can only reduce to a certain value if a converged steady state solution is required. I define 'convergent solution' as max residuals drop below 1e-6 and no significant oscillations for the monitored variables.

Max residuals for 3D momentum, continuity & turbulence become unconverged & unstable if the near wall mesh size go below this value. I shall be obliged if anyone can tell me the possible causes of errors for this problem?

I'm modelling a 3D bend diffuser (steady flow) at the moment. Have tried both steady & unsteady RANS solver. Same problems occurred at smaller near wall element size. No problem found for 2 equation model. BC: inlet-total pressure, outlet- static pressure. Standard 5% turbulent intensity applied at both inlet & outlet (if reversed flow occurred).

Thanks for help.

When you mention the size of the near-wall element, what do you mean by that? Is it in the normal direction from the wall?

Which type of spatial discretisation scheme do you use in your turbulence model? What kind of realizability enforcements do you have in your code?