# Steady state verses Time accurate simulations

 Register Blogs Members List Search Today's Posts Mark Forums Read

 May 21, 2003, 09:54 Steady state verses Time accurate simulations #1 Saud khashan Guest   Posts: n/a It seems that two-equation RANS models dampen (or kill) the unsteadiness of problems that is known to be "very" transient, like the sub-critical flow past a circular cylinder. They kill the unsteadiness so that a steady-state simulation can be used which in turn results in a converged steady-stae like solution. The total, local pressure and drag coefficients obtained using this steady stae simulations (i.e. by dropping the transient term in the RANS equation) were comparable to the time-averaged coefficients I obtained using the time-accurate simulation. This made me believe that the dissipative effect of these models overwights any numerical dissipation a discretization scheme can cause. I wonder if some one will comment on such observation and then help me understand the reason behind that. I am particulary, interested in the effect of dropping the transient term on the pressure term in RANS equation. Thanks I will appreciate any comment

 May 22, 2003, 11:13 Re: Steady state verses Time accurate simulations #2 xing zhang Guest   Posts: n/a I am also interested in the explanation for this. I know that some researchers claimed that they can use the two-equation model to predict unsteady flows such like vortex shedding, but others claimed that only RSM models work. I guess this is related to the Boussinesq¡¯s hypothesis in the two-equation model.

 May 23, 2003, 07:00 Re: Steady state verses Time accurate simulations #3 Anton Lyaskin Guest   Posts: n/a May be I don't understand the problem, but I do have an experience of modelling unsteady flow with two-equation model (k-epsilon RNG, to be exact). I was vortex shedding at the circular cylinder.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Chander Main CFD Forum 5 December 23, 2013 06:31 jing113cn FLUENT 2 January 15, 2010 04:18 Steve Main CFD Forum 2 March 25, 2008 09:39 liugx212 OpenFOAM Running, Solving & CFD 3 January 4, 2006 19:07 Lisa Main CFD Forum 11 July 5, 2000 14:37

All times are GMT -4. The time now is 15:49.