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-   -   LES and DES models for wind turbine (http://www.cfd-online.com/Forums/main/87394-les-des-models-wind-turbine.html)

mohammad April 19, 2011 09:31

LES and DES models for wind turbine
 
Hi everybody,
I'm simulating the NREL wind turbine.My model is based on SST.For wind speed 5.4 m/s and Physical time scales as follow I have the following results;

Time scale: 0.1----> exactly Not converged (No. of Iteration 400)
Time scale: 0.06----> very hard to say converged (No. of Iteration 1000)
Time scale: 0.01----> ???? but very hard to say it will converge( still running)

As I know, I can use LES or DES for the situations that RANS-based models are not good because of large area of separation.I searched in CFX to run my model with LES or DES but I didn't find it....

Now is there anybody to tell my how I can start with LES or DES?

Thanks in advance

cfd_newbie April 19, 2011 22:02

Quote:

Originally Posted by mohammad (Post 304229)
Hi everybody,
I'm simulating the NREL wind turbine.My model is based on SST.For wind speed 5.4 m/s and Physical time scales as follow I have the following results;

Time scale: 0.1----> exactly Not converged (No. of Iteration 400)
Time scale: 0.06----> very hard to say converged (No. of Iteration 1000)
Time scale: 0.01----> ???? but very hard to say it will converge( still running)

As I know, I can use LES or DES for the situations that RANS-based models are not good because of large area of separation.I searched in CFX to run my model with LES or DES but I didn't find it....

Now is there anybody to tell my how I can start with LES or DES?

Thanks in advance

Dear mohammad,
1. Why are you running with Physical time scale, just choose the auto time scale option.
2. Have you made your grid correctly ? Take hint from many papers availaible for CFD simulation of NREL.
3. Try the new Menter-langley transitional model available in CFX for this. I think I have told you about the paper related to it.

mohammad April 19, 2011 22:36

Quote:

Originally Posted by cfd_newbie (Post 304314)
Dear mohammad,
1. Why are you running with Physical time scale, just choose the auto time scale option.
2. Have you made your grid correctly ? Take hint from many papers availaible for CFD simulation of NREL.
3. Try the new Menter-langley transitional model available in CFX for this. I think I have told you about the paper related to it.

Hi cfd-newbie,
I remember that suggestion that you gave me; thanks again. and about your questions:

1- The speed of convergence with a appropriate Phy. time scale is much faster than auto time scale.( I think and i tested it)

2-I think my model is acceptable enough.( see my answer to Glenn Horrocks)
+ I'm now in the middle of this way...I want to finish the current runs first and then to check your idea i will do a mesh-sensitivity-analysis. Later, I will shift to your suggestion about "Menter-langley ".... [It's a long way...isn't it?? :) ]

3- As i told you, still i haven't read that paper. but one question; is "new Menter-langley " method available in CFX 10?

Thanks

cfd_newbie April 20, 2011 01:21

Quote:

Originally Posted by mohammad (Post 304318)
Hi cfd-newbie,
I remember that suggestion that you gave me; thanks again. and about your questions:

1- The speed of convergence with a appropriate Phy. time scale is much faster than auto time scale.( I think and i tested it)

2-I think my model is acceptable enough.( see my answer to Glenn Horrocks)
+ I'm now in the middle of this way...I want to finish the current runs first and then to check your idea i will do a mesh-sensitivity-analysis. Later, I will shift to your suggestion about "Menter-langley ".... [It's a long way...isn't it?? :) ]

3- As i told you, still i haven't read that paper. but one question; is "new Menter-langley " method available in CFX 10?

Thanks

Hi Mohammad,
1. I think your first priority should be to get accurate results (even if it takes little more time with Auto timescale at least you will get convergence) instead of putting time on finding best Physical timescale.

2. Good to know that.

3. Langley menter model is relatively new compared to other turbulence models. It's available in CFX for more than couple of years now.

Raashid

mohammad April 30, 2011 00:11

Quote:

Originally Posted by cfd_newbie (Post 304328)
Hi Mohammad,
1. I think your first priority should be to get accurate results (even if it takes little more time with Auto timescale at least you will get convergence) instead of putting time on finding best Physical timescale.

2. Good to know that.

3. Langley menter model is relatively new compared to other turbulence models. It's available in CFX for more than couple of years now.

Raashid

Dear Raashid...
I have done the mesh sensitivity analysis and I want to refer you to my new question...
http://www.cfd-online.com/Forums/mai...tml#post305659

I hope you can help me....

Cheers

cfd_newbie April 30, 2011 21:48

Quote:

Originally Posted by mohammad (Post 305660)
Dear Raashid...
I have done the mesh sensitivity analysis and I want to refer you to my new question...
http://www.cfd-online.com/Forums/mai...tml#post305659

I hope you can help me....

Cheers

ASAK Mohammad,
The link that you have posted in broken can you check and repost the link :(
Raashid

mohammad April 30, 2011 22:01

Quote:

Originally Posted by cfd_newbie (Post 305737)
ASAK Mohammad,
The link that you have posted in broken can you check and repost the link :(
Raashid

Hi Raashid.....The website officials have changed the location of my post...this is the new address of that link...
http://www.cfd-online.com/Forums/cfx...tml#post305691


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