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-   -   Bounding OMEGA (http://www.cfd-online.com/Forums/openfoam/66407-bounding-omega.html)

barath.ezhilan July 14, 2009 14:20

Bounding OMEGA
 
Hi all,

I am simulating flow in a draft tube using transient SimpleFoam k-omega SST model and k-omega SSTF filter model added by Hakan Nilson

I have a basic doubt!!

In certain time steps i am getting lines which say

bounding omega, min: -1.15066 max: 11926.8 average: 522.558

But the solution converges still. (I have experienced similar cases where the bounding min and max values keep increasing and stops)

I would like to know, is the solution correct or not??

farahiam June 8, 2011 20:36

Hi Barath,
I am facing the same problem as yours. I am using the k-w SST turbulence model and during iteration, I have both bounding k and omega. The min and max values are between 1e-6 to 1e+6.
FYI, I applied boundary layers on my car (it's an external aerodynamics of car in a wind tunnel case) - about 10 layers and the y+ values are between 0 to 100 (average of about 30).

I think it is because of my y+ values but I am not really sure. If it's true, then should I increase my y+ values by making the layers nearest to wall to be thicker?
Could anyone help me on this?


Regards,
Ayu

Balakrshnan Ramakrishnan June 9, 2011 04:55

Hi ,
I had a similar problem of very extreme values of k and epsilon (it was a wind simulation case). Then I tried reducing the relaxation factors for k and epsilon. I gave very low value like 0.01. Of course the simulation took a long time, but the bounding values did not go to extremes.

Try it out and let me know.

Cheers,
Balakrshnan Ramakrishnan

deepaktbabu April 20, 2012 11:06

it is not working for me :(
can you give me another method to reduce the bounding variables


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