CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM (http://www.cfd-online.com/Forums/openfoam/)
-   -   Bounding epsilon or bounding omega (http://www.cfd-online.com/Forums/openfoam/73920-bounding-epsilon-bounding-omega.html)

Stylianos March 19, 2010 10:51

Bounding epsilon or bounding omega
 
Hello Everyone

I'm trying to run an axial turbine simulation via MRFSimpleFoam (Rotor-Stator with GGI interface), i've tried both kEpsilon and kOmegaSST turb-models but i get either bounding omega (in case of the kOmega) or bounding epsilon (in case of kEpsilon) with negative values dose anyone have any idea about that?

i use:
inlet:
U
: flowRateInletVelocity
p: zeroGradient
k: turbulentIntensityKineticEnergyInlet
epsilon: turbulentMixingLengthDissipationRateInlet
omega: turbulentMixingLengthFrequencyInlet

outlet:
U: inletOutlet
p: fixedMeanValue
k/epsilon/omega: inletOutlet

with turbulentIntensity = 5%
and MixingLength = 0.079 (1/5*(smaller diameter of my duct))

Stelios

Stylianos March 23, 2010 07:21

Managed to get kOmegaSST running,
Had to initialize omega field with omega = epsilon/(Cm*k) and not epsilon/k as mentioned in several threads.

no luck with kEpsilon thought.

Hope this is useful for someone,
Stelios

mrshb4 November 3, 2010 06:21

the same problem
 
Dear Stelios
I have the same problem with my case that is a centrifugal fan with a duct, my boundary condition is almost similar to you. First, my model would diverge at about 10 iterations.(k and epsilon would blow up). I changed my fvSchemes and fvSolutions dictionaries and got better answers. At least with no divergence until about 200 iterations, but after that it would diverge again.

Could you solve your problem?
It you could, tell me what you did.

Good luck
Mohamadreza

Stylianos November 4, 2010 05:49

Hello Mohamad

The only think i managed to do to get a solution was to use kOmegaSST turbulence model instead of kEpsilon. But that was some time ago and with OF 1.5-dev i don't know if there is something else going on in 1.6.

Stelios

kaka22 November 10, 2010 02:03

Hi Stelios,

I am using kOmegaSST turbulence model in rhoPisoFoam. I am getting bounding omega with negative values. I have also given initial value of omega, still bounding omega is appearing. My case is not crashing but it's also not showing the right flow profile. I'm guessing the problem lies with the bounding omega. Is there any suggestion that bounding omega can be eliminated by changing any of the parameters? Thanks!

Novi

farahiam June 9, 2011 00:40

Hi Kaka,
Have you solved the problem?
I am also facing similar problem as yours..

Ayu


All times are GMT -4. The time now is 17:04.