Spalart Allmaras DDES - circular cylinder

albertofast · February 24, 2013, 09:43

Dear OpenFOAM users,
I want to make some aeroacoustical simulations coupling OpenFOAM with an opensource acoustic simulation code.
I am trying to simulate the von-karman vortex street after a circular cylinder at Re=166000. After performing 2D incompressible simulation with pimpleFoam solver and a k-omega SST turbulence model (getting quite good results in term of force Coefficients and Strouhal number), I would like to improve my simulation using the Spalart Allmaras DDES hybrid turbulence model. I made few tests (2D case), but I'm getting a non-physical behaviour (look at the animation). I also attached the case-study folder.
I would be very pleased to you if you could get me some suggestions.
Thank you very much!

1)DDES case-study: https://mega.co.nz/#!osgCHZYB!Vf4Yxg...TxQfzgX-sgWeGw
2)DDES animation (U magnitude):
https://mega.co.nz/#!JlxVQCCI!E0xGLS...cUx-AD5TmCu-1o
3) komegaSST case-study:
https://mega.co.nz/#!JgYDwSob!T9EYAl...5bG53ncqcMSWcA
4)komegaSST animation:
https://mega.co.nz/#!dkZmmIwB!KVs80U...TtuPfh6eXrYZnQ

PS: Sorry , I moved this thread which was previously posted in the wrong section, thanks!

kkpal · April 9, 2013, 09:19

the website you posted does not work. Your cases can not be downloaded!

albertofast · April 9, 2013, 10:25

Hello!
I've just checked the links and they work! Can you please specify what kind of problem the browser gives you?
Thanks!

skeptik · April 9, 2013, 10:38

For my browser it needs to set up Flash.

But i have one question about your case. Did you use empty BC with one cell thick domain both in SST and DES case?

fsaltara · April 10, 2013, 10:40

I think that you can't use DDES in a 2D simulation. DDES is a hybrid RANS-LES method in which you should capture the large 3D eddies in the wake. In a 2D simulation you are going to miss the effect of the vortex stretching that is important in the energy cascade process.
Probably this is the explanation for the non-physical results that you got.

f0208secretx · August 1, 2015, 23:53

Quote:

Originally Posted by albertofast

Hello!
I've just checked the links and they work! Can you please specify what kind of problem the browser gives you?
Thanks!

Its always great when someone shares a case file to help us novice..

I was wondering if you have made the SA-DDES model work and for more complicated geometries? If yes, would you mind sharing your discovery? Thanks!

er_trebbia · August 5, 2015, 11:33

Hi f0208secretx

Basically, I have to perform a S-A DDES, and I am trying to modify the channel395 tutorial case for the beginning, then I will go to a (very) more complex geometry.
I would suggest you to do the same. I will post a tutorial as soon as possible.

February 24, 2013, 09:43	Spalart Allmaras DDES - circular cylinder	#1
albertofast New Member edoardo Join Date: Nov 2010 Posts: 8 Rep Power: 16	Dear OpenFOAM users, I want to make some aeroacoustical simulations coupling OpenFOAM with an opensource acoustic simulation code. I am trying to simulate the von-karman vortex street after a circular cylinder at Re=166000. After performing 2D incompressible simulation with pimpleFoam solver and a k-omega SST turbulence model (getting quite good results in term of force Coefficients and Strouhal number), I would like to improve my simulation using the Spalart Allmaras DDES hybrid turbulence model. I made few tests (2D case), but I'm getting a non-physical behaviour (look at the animation). I also attached the case-study folder. I would be very pleased to you if you could get me some suggestions. Thank you very much! 1)DDES case-study: https://mega.co.nz/#!osgCHZYB!Vf4Yxg...TxQfzgX-sgWeGw 2)DDES animation (U magnitude): https://mega.co.nz/#!JlxVQCCI!E0xGLS...cUx-AD5TmCu-1o 3) komegaSST case-study: https://mega.co.nz/#!JgYDwSob!T9EYAl...5bG53ncqcMSWcA 4)komegaSST animation: https://mega.co.nz/#!dkZmmIwB!KVs80U...TtuPfh6eXrYZnQ PS: Sorry , I moved this thread which was previously posted in the wrong section, thanks!

April 9, 2013, 10:38		#4
skeptik Member Ilya Join Date: Dec 2011 Location: Russia Posts: 97 Blog Entries: 41 Rep Power: 15	For my browser it needs to set up Flash. But i have one question about your case. Did you use empty BC with one cell thick domain both in SST and DES case? __________________ practice makes perfect

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April 9, 2013, 09:19		#2
kkpal Senior Member Join Date: Jan 2013 Posts: 135 Rep Power: 13	the website you posted does not work. Your cases can not be downloaded!

April 9, 2013, 10:25		#3
albertofast New Member edoardo Join Date: Nov 2010 Posts: 8 Rep Power: 16	Hello! I've just checked the links and they work! Can you please specify what kind of problem the browser gives you? Thanks!

April 10, 2013, 10:40		#5
fsaltara New Member Join Date: Mar 2009 Posts: 21 Rep Power: 18	I think that you can't use DDES in a 2D simulation. DDES is a hybrid RANS-LES method in which you should capture the large 3D eddies in the wake. In a 2D simulation you are going to miss the effect of the vortex stretching that is important in the energy cascade process. Probably this is the explanation for the non-physical results that you got.

August 5, 2015, 11:33		#7
er_trebbia New Member Join Date: May 2013 Posts: 9 Rep Power: 13	Hi f0208secretx Basically, I have to perform a S-A DDES, and I am trying to modify the channel395 tutorial case for the beginning, then I will go to a (very) more complex geometry. I would suggest you to do the same. I will post a tutorial as soon as possible.