Convergence criteria

PrandtlGlawert · August 13, 2009, 17:12

Dear all:
I´m modelling a WORTMANN profile and studying its behaviour (Re=3x10^5). K-w (SST) model seems to reach convergence quick, but when switching to Reynolds Stress turbulence modelling, convergence tends to take far more time. That wouldn´t matter if it weren´t because i can never get a single value, just a range of them, and i can only take a semivalue...Is that correct? Any ideas to reach convergence?

(By the way, i have to study later the same model with k-kl-w turbulence modelling and i´ve run a few cases... OMG convergence seems impossible there!!!!

)

Thx in advance...

tstorm · August 13, 2009, 18:06

The problem with the RSM is the tight coupling of the Reynolds Stress transport equations. It's very difficult to get that model to converge. I don't know what a wortmann profile is, but if it involves strong pressure gradients, separation, transition, or other complicated features it might be tough. In my experience, the best way to get RSM cases to converge is to start with a very nice mesh - smaller cells than you'd use with an eddy viscosity model and more attention to skewness.
Good luck!

August 13, 2009, 17:12	Convergence criteria	#1
PrandtlGlawert New Member Daniel LLanes Join Date: Aug 2009 Posts: 11 Rep Power: 16	Dear all: I´m modelling a WORTMANN profile and studying its behaviour (Re=3x10^5). K-w (SST) model seems to reach convergence quick, but when switching to Reynolds Stress turbulence modelling, convergence tends to take far more time. That wouldn´t matter if it weren´t because i can never get a single value, just a range of them, and i can only take a semivalue...Is that correct? Any ideas to reach convergence? (By the way, i have to study later the same model with k-kl-w turbulence modelling and i´ve run a few cases... OMG convergence seems impossible there!!!! ) Thx in advance...

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Convergence criteria	PrandtlGlawert	Main CFD Forum	1	August 13, 2009 17:13
star-ccm+ convergence criteria	star	Siemens	2	January 14, 2009 04:57
Convergence Criteria	edwin	FLUENT	1	February 14, 2008 19:24
Convergence criteria	Gaurav	Siemens	0	February 3, 2006 04:53
Convergence criteria	Sileno	Phoenics	1	December 6, 2005 07:25

August 13, 2009, 18:06		#2
tstorm Member Join Date: Apr 2009 Posts: 78 Rep Power: 17	The problem with the RSM is the tight coupling of the Reynolds Stress transport equations. It's very difficult to get that model to converge. I don't know what a wortmann profile is, but if it involves strong pressure gradients, separation, transition, or other complicated features it might be tough. In my experience, the best way to get RSM cases to converge is to start with a very nice mesh - smaller cells than you'd use with an eddy viscosity model and more attention to skewness. Good luck!