|
[Sponsors] |
![]() |
![]() |
#1 |
Member
Lorenzo Mazzei
Join Date: Dec 2010
Posts: 60
Rep Power: 15 ![]() |
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? |
|
![]() |
![]() |
![]() |
![]() |
#2 |
Member
Lorenzo Mazzei
Join Date: Dec 2010
Posts: 60
Rep Power: 15 ![]() |
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. |
|
![]() |
![]() |
![]() |
![]() |
#3 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,816
Rep Power: 144 ![]() ![]() ![]() ![]() |
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. |
|
![]() |
![]() |
![]() |
![]() |
#4 |
Member
Lorenzo Mazzei
Join Date: Dec 2010
Posts: 60
Rep Power: 15 ![]() |
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.
|
|
![]() |
![]() |
![]() |
![]() |
#5 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,816
Rep Power: 144 ![]() ![]() ![]() ![]() |
Yes, you should always use a physical time scale on the final run to convergence. You cannot judge convergence by residuals alone.
|
|
![]() |
![]() |
![]() |
Tags |
cfx, convergence, residual, turbulence |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
how to define turbulent intensity in 2d problem | blueberry | FLUENT | 1 | March 13, 2013 09:09 |
Convergence problem for P1 & Energy | HP | FLUENT | 5 | May 21, 2005 15:01 |
convergence problem | Trushar | Phoenics | 5 | August 27, 2002 23:40 |
convergence problem with SIMPLER | NURAY KAYAKOL | Main CFD Forum | 1 | February 24, 1999 13:43 |
the turbulent problem | Daejin, Kang | Main CFD Forum | 0 | November 16, 1998 10:52 |