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Old   April 19, 2011, 09:31
Smile LES and DES models for wind turbine
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mohammad
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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
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Old   April 19, 2011, 22:02
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Raashid Baig
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Quote:
Originally Posted by mohammad View Post
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.
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Old   April 19, 2011, 22:36
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Quote:
Originally Posted by cfd_newbie View Post
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
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Old   April 20, 2011, 01:21
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Quote:
Originally Posted by mohammad View Post
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
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Old   April 30, 2011, 00:11
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Quote:
Originally Posted by cfd_newbie View Post
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
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Old   April 30, 2011, 21:48
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Raashid Baig
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Quote:
Originally Posted by mohammad View Post
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
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Old   April 30, 2011, 22:01
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Quote:
Originally Posted by cfd_newbie View Post
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...
Strange...can you tell me why???
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