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

LES or DES in wind turbine

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 19, 2011, 09:41
Smile LES or DES in wind turbine
  #1
Senior Member
 
mohammad
Join Date: Dec 2010
Location: Seoul, South korea
Posts: 210
Rep Power: 7
mohammad is on a distinguished road
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
mohammad is offline   Reply With Quote

Old   April 19, 2011, 21:23
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,651
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
First work though the suggestions here:
http://www.cfd-online.com/Wiki/Ansys...gence_criteria

Before you do any LES/DES stuff make sure you do some thorough reading into the approaches. If you do not understand what it is doing you have no hope of getting an accurate answer.
ghorrocks is offline   Reply With Quote

Old   April 19, 2011, 22:16
Smile
  #3
Senior Member
 
mohammad
Join Date: Dec 2010
Location: Seoul, South korea
Posts: 210
Rep Power: 7
mohammad is on a distinguished road
Dear Glenn Horrocks,
First of all thanks for your reply.
I have read and used this FAQ before and it's interesting that I have already got acceptable results (based of the information of this FAQ) for my model with velocities between 6 to 13 m/s with appropriate accuracy.
(not for v=5.4m/s as yet )

What I found during those runs is in contradiction with hint No.3 of FAQ notes.I did ,somewhat, a timescale sensitivity test .I run my model with wind speed 10.3 m/s with different Physical timescales of {0.01,0.02,0.05,0.06,0.07,0.08,0.1, 0.15}.
What I found was that when the model had a poor( say no) convergence with a large Physical Time scale it would have better convergence with smaller ones.This is against what is shown in FAQ.???!!!

The second question here is the suggestion to increase physical time scale presented in FAQ is also in contradiction with what is presented under the title of "Steady State Time Scale Control" in CFX help mannual which recommend use of small physical time scale.

The Last thing that I think it's useful, is that my model will have large area of separation and I think naturally it contains natural instabilities like vortexes and...that's why I think I need to test it with LES/DES models...

I will be really thankful to know your opinion.
mohammad is offline   Reply With Quote

Reply

Tags
des, les, wind turbine

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wind turbine simulation Saturn CFX 34 October 16, 2014 05:27
Ducted wind turbine (BC for the shroud) Pepita CFX 4 June 29, 2013 07:09
LES and DES models for wind turbine mohammad Main CFD Forum 6 April 30, 2011 22:01
please help in simulating a wind turbine blade in 6 DOF ????.... usman naseer Main CFD Forum 0 December 11, 2009 02:51
Wind turbine simulation Saturn FLUENT 1 June 16, 2006 02:12


All times are GMT -4. The time now is 18:10.