CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > SU2

Distinction between k-w sst and SA turbulence model in SU2

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   December 3, 2021, 03:46
Default Distinction between k-w sst and SA turbulence model in SU2
  #1
Senior Member
 
Arijit Saha
Join Date: Feb 2019
Location: Singapore
Posts: 132
Rep Power: 7
ari003 is on a distinguished road
Hello everyone,
Note:- Shifted this thread from news and announcement section to general question section.
Hope you all are doing well. I came across a specific doubt that might be very simple for others and I would really appreciate if they can share their understanding with me. The description is as follows:-

I am running an airfoil simulation at M=0.8 with k-w SST and S-A turbulence model. My aim was to analyze how the y+ varies along the upper surface of the airfoil and the plot is attached beneath. Also, there is a significant difference in Cl value for the both, 0.26 for k-w SST while 0.025 for S-A. I am wondering what causing this huge difference in Cl values?
If I take a dig in y+ formulation it seems like the eddy viscosity calculation in both the case is making the difference.

So my question is, whether the script for the SA case (attached) is in correct order or not? Also, if anyone is aware of SA-LM or SA-BC does either of the one will give better result compared to standard S-A model in case of airfoil case?
Attached Images
File Type: jpg untitled1.jpg (77.4 KB, 29 views)
Attached Files
File Type: zip OS_Single3.zip (2.8 KB, 7 views)
ari003 is offline   Reply With Quote

Old   December 3, 2021, 06:27
Default
  #2
Senior Member
 
bigfoot
Join Date: Dec 2011
Location: Netherlands
Posts: 662
Rep Power: 20
bigfootedrockmidget is on a distinguished road
Hi,


Not sure about the difference in CL, but for transition you should use the BC model, the LM model has been deactivated and needs to be reimplemented.


Regarding the difference in CL, what is available in the literature? There are probably studies out there where the SA and SST model were used in the same study for this or a similar airfoil. A quick google search shows some images of the Cl(alpha) curve for SA and k-omega-SST with significant differences. Doesn't mean it cannot be a problem in the SU2 code, but this would be the first to check.
bigfootedrockmidget is offline   Reply With Quote

Old   January 5, 2022, 10:40
Default
  #3
New Member
 
Join Date: Dec 2013
Location: Italy
Posts: 29
Rep Power: 13
Jiba is on a distinguished road
Hi,

looking a the Y+, the first thing I spot is that separation seems to be predicted at different locations. This can be easily confirmed comparing the cf. If this is the case, surely the comparison of cp will show differences and explain the different cl, even though the difference is too high.

From the cfg file, the simulation is run at AoA=0 deg, but the header (maybe not updated) refers to a symmetrical airfoil.? If this is the case, cl must be equal to zero.

An additional comment is that Y+ should be a bit smaller.
Jiba is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 06:40.