Steady state verses Time accurate simulations
It seems that twoequation RANS models dampen (or kill) the unsteadiness of problems that is known to be "very" transient, like the subcritical flow past a circular cylinder. They kill the unsteadiness so that a steadystate simulation can be used which in turn results in a converged steadystae 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 timeaveraged coefficients I obtained using the timeaccurate 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 
Re: Steady state verses Time accurate simulations
I am also interested in the explanation for this.
I know that some researchers claimed that they can use the twoequation 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 twoequation model. 
Re: Steady state verses Time accurate simulations
May be I don't understand the problem, but I do have an experience of modelling unsteady flow with twoequation model (kepsilon RNG, to be exact). I was vortex shedding at the circular cylinder.

All times are GMT 4. The time now is 15:51. 