problem with SST k-omega model

avi031 · January 25, 2012, 05:10

Hi,
I have used SST k-omega model, Realizable and RNG k-epsilon models for a problem involving heat transfer in a duct (internal flow) with a lot separation, reattachment and re-circulations at near-wall regions. Significant differences in wall temperatures are seen between the turbulence models.
Unfortunately very high wall temperatures are obtained with the usage of SST k-omega model compared to the k-epsilon models, which has resulted in bad-comparison with the literature. This finding is contrary to other numerical simulation papers. The re-circulation size in case of SST k-omega model is also very different from the k-epsilon models.
y+ less than 1 was maintained for all the cases.

The reason for high temperatures with the usage of SST k-omega model evades me. Please let me know of your suggestions, as to what can be wrong.

Regards
Avinash

swiftaircraft · January 26, 2012, 15:38

What other options within the sst model have you turned on?

avi031 · January 27, 2012, 00:43

SST model with Low-Re corrections was used for the simulation

swiftaircraft · January 27, 2012, 04:48

I would turn off this option as by default the k-omega model can resolve through the boundary layer without any corrections being required. My experience with this option in the past has not been that good.

shaoda169 · January 27, 2012, 06:53

Quote:

Originally Posted by swiftaircraft

I would turn off this option as by default the k-omega model can resolve through the boundary layer without any corrections being required. My experience with this option in the past has not been that good.

The low-reynolds correction option is borrowed from the original k-w model rather than being in the sst k-w equations. It is said that this option should be used with cautions.

heidar · January 29, 2012, 18:24

Hello

i Have used the all turbulent model for a ribbed roughened square duct. my reynolds number was from 10000 to 100000 in low reynolds number SST model was very bad and for higher than 25000 RNG, RM, SST, and etc exhebited good results
could you tell me more about your dimensions and reynolds number.
As you know the SST model uses K-w in near the wall and uses K-e in far feild if you give more details we could merge in it

Best Regards
Heidar Jafarizadeh

January 25, 2012, 05:10	problem with SST k-omega model	#1
avi031 New Member Avinash Join Date: Jan 2011 Posts: 18 Rep Power: 15	Hi, I have used SST k-omega model, Realizable and RNG k-epsilon models for a problem involving heat transfer in a duct (internal flow) with a lot separation, reattachment and re-circulations at near-wall regions. Significant differences in wall temperatures are seen between the turbulence models. Unfortunately very high wall temperatures are obtained with the usage of SST k-omega model compared to the k-epsilon models, which has resulted in bad-comparison with the literature. This finding is contrary to other numerical simulation papers. The re-circulation size in case of SST k-omega model is also very different from the k-epsilon models. y+ less than 1 was maintained for all the cases. The reason for high temperatures with the usage of SST k-omega model evades me. Please let me know of your suggestions, as to what can be wrong. Regards Avinash heidar likes this.

January 27, 2012, 04:48		#4
swiftaircraft Member David Stanbridge Join Date: Apr 2010 Location: Norwich, UK Posts: 59 Rep Power: 16	I would turn off this option as by default the k-omega model can resolve through the boundary layer without any corrections being required. My experience with this option in the past has not been that good. heidar likes this.

January 29, 2012, 18:24	Very nice	#6
heidar Member heidar jafarizadeh Join Date: Mar 2010 Location: Iran- Tehran Posts: 43 Rep Power: 16	Hello i Have used the all turbulent model for a ribbed roughened square duct. my reynolds number was from 10000 to 100000 in low reynolds number SST model was very bad and for higher than 25000 RNG, RM, SST, and etc exhebited good results could you tell me more about your dimensions and reynolds number. As you know the SST model uses K-w in near the wall and uses K-e in far feild if you give more details we could merge in it Best Regards Heidar Jafarizadeh

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January 26, 2012, 15:38		#2
swiftaircraft Member David Stanbridge Join Date: Apr 2010 Location: Norwich, UK Posts: 59 Rep Power: 16	What other options within the sst model have you turned on?

January 27, 2012, 00:43		#3
avi031 New Member Avinash Join Date: Jan 2011 Posts: 18 Rep Power: 15	SST model with Low-Re corrections was used for the simulation