Bounding OMEGA

barath.ezhilan · July 14, 2009, 15:20

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, 21:36

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, 05:55

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, 12:06

it is not working for me

can you give me another method to reduce the bounding variables

July 14, 2009, 15:20	Bounding OMEGA	#1
barath.ezhilan New Member Barath Ezhilan Join Date: Jun 2009 Posts: 20 Rep Power: 17	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??

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June 8, 2011, 21:36		#2
farahiam New Member farahidayu Join Date: Aug 2010 Posts: 20 Rep Power: 16	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

June 9, 2011, 05:55		#3
Balakrshnan Ramakrishnan New Member BR Join Date: May 2009 Posts: 23 Rep Power: 17	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

April 20, 2012, 12:06		#4
deepaktbabu New Member deepaktbabu Join Date: Nov 2011 Posts: 5 Rep Power: 15	it is not working for me can you give me another method to reduce the bounding variables