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Old   January 19, 2010, 09:21
Default Bounding turbulence values
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varun
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Hi,

How to change the bounding values for the turbulence parameters such as "k" and "Omega"? My simulation crashes due to "omega" becoming very low of the order of 1e-18. How can i overcome this problem. I am using K-omega + SST model.


ThnX!!

varun
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Last edited by vw.cfd; January 20, 2010 at 04:18.
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Old   June 8, 2011, 20:29
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farahidayu
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Hi Varun,
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
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Old   June 9, 2011, 04:58
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Balakrshnan Ramakrishnan
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Quote:
Originally Posted by vw.cfd View Post
My simulation crashes due to "omega" becoming very low of the order of 1e-18. !
Hi Varun,
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
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