C3X Fully turbulent convergence problem
 

Hi all, I'm doing a comparison with C3X 1988 blade test case between SST Fully turbulent, Gamma model (Reth=250) and Gamma-Theta model. Every case starts with High order advection scheme, High order turbulence, Local timescale factor 5.
During my runs I experimented very good convergence in second and third case, but in the first one the solution doesn't converge, with mom residuals between 10-3 and 10-4.
I tried increasing the time step, without any enhancement. The mesh has a good y+ quality, except for the trailing edge (y+ max approximately 5), but unfortunately i can't modify it.
Any suggestions to achieve convergence?

ok, i decided the solution has converged. Although residuals didn't fall, the temperature of the solid is stable and also the imbalance.
Unfortunately I still haven't found an explanation for that behaviour.

http://www.cfd-online.com/Wiki/Ansys...gence_criteria

Also note you should use local time scale factor to convergence. You should switch to physical time scale for the final run to convergence.

Thank you Glenn. I've already read the documentation. About your last statement: that step is recommended in every case? Because, except for the fully turbulent case, in the other cases all parameters are steady and residuals are below 10-6.

Yes, you should always use a physical time scale on the final run to convergence. You cannot judge convergence by residuals alone.