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

Stall behavior w/ initialization from previous results

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 16, 2017, 13:46
Post Stall behavior w/ initialization from previous results
  #1
Member
 
Lucas Barreto
Join Date: Sep 2017
Location: São Paulo, Brazil
Posts: 35
Rep Power: 7
lcbarreto is on a distinguished road
Hi guys,

I am simulating the flow over an aircraft. I have already done my mesh convergence study and I found a optimum mesh for my case. Right now I am developing my drag polar so I am varying my angle of attack (AoA) from -10 to 20 in order to find the behavior of my CL, CD and CM.

I have tried 2 different approaches:
1) I ran my simulations, close to the stall, manually and I have tested initializing them with both standard and Hybrid methods and I am getting a stall angle of 11 deg. Above 11 I get a transient flow which is expected for stalled stages.

2) I have parametrized my AoA in order to use my table of design points and automatize my simulations. For the initialization I am using the data from the previous solution so when I ran for 11 degrees I initialize with the data obtained on my simulation with 10 deg. The simulations runs very similar to the method 1 for the linear part of the CL vs Alpha curve, but I am getting a higher stall angle (approximately 14.5 deg) and also a higher CL max And I get a convergence for CL, Cd CM, continuity, momentum and nut very qick with a factor of 10e-5.

I know that the initial guess is very important for a numerical methods, however I am not sure if it would make that difference or if there is something wrong with my simulations. Has anyone experienced this kind of behavior before?

Thanks in advance

Last edited by lcbarreto; October 16, 2017 at 15:17.
lcbarreto is offline   Reply With Quote

Old   October 17, 2017, 02:40
Default
  #2
Member
 
Jaesan Yoon
Join Date: Sep 2017
Posts: 36
Rep Power: 7
litzj is on a distinguished road
I cannot memorize the title of specific paper, but load previous aoa data is appropriate approach for post stall aoa...

Maybe there is a aiaa paper dealing that issue.

vortex or separated flow is well developed when load previous aoa result
litzj is offline   Reply With Quote

Old   October 17, 2017, 06:33
Default
  #3
Member
 
Lucas Barreto
Join Date: Sep 2017
Location: São Paulo, Brazil
Posts: 35
Rep Power: 7
lcbarreto is on a distinguished road
Quote:
Originally Posted by litzj View Post
I cannot memorize the title of specific paper, but load previous aoa data is appropriate approach for post stall aoa...

Maybe there is a aiaa paper dealing that issue.

vortex or separated flow is well developed when load previous aoa result
Hi Jaesan, thanks for the reply.

So you're saying that the approach of loading previous aoa result is a better first guess for the simulation right? I just didn't think would make that big difference.
lcbarreto is offline   Reply With Quote

Old   October 17, 2017, 09:34
Default
  #4
Member
 
Jaesan Yoon
Join Date: Sep 2017
Posts: 36
Rep Power: 7
litzj is on a distinguished road
developing vortex or separated region on the airfoil is sensitive to initial status.

At high AoA, data from previous AoA is not only helping right solution, also helping for stability and convergence of the solution
litzj is offline   Reply With Quote

Old   October 17, 2017, 11:30
Default
  #5
Member
 
Lucas Barreto
Join Date: Sep 2017
Location: São Paulo, Brazil
Posts: 35
Rep Power: 7
lcbarreto is on a distinguished road
Quote:
Originally Posted by litzj View Post
developing vortex or separated region on the airfoil is sensitive to initial status.

At high AoA, data from previous AoA is not only helping right solution, also helping for stability and convergence of the solution
Thank you very much for the help!
lcbarreto is offline   Reply With Quote

Reply

Tags
aerodynamic, cfd, fluent, initialization method

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Different Results from Fluent 5.5 and Fluent 6.0 Rajeev Kumar Singh FLUENT 6 December 19, 2010 11:33
Importing previous results as a starting point for future simulations mcintoshjamie FLUENT 1 November 15, 2009 06:38
Using results form previous run as inlet condition lauren CFX 3 June 9, 2008 13:32
Using results form previous run as inlet condition M CFX 2 January 16, 2006 22:43
previous solution results as input San FLUENT 3 September 6, 2005 21:56


All times are GMT -4. The time now is 18:55.