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January 14, 2014, 20:09 
Want to implement a turbuence model! How?

#1 
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David
Join Date: Feb 2013
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My advisor want me to implement a 2equation turbulence model, like KW or KE, I am wondering those two equations, should I simultaneously solve them together with NS equations?
Or, can I solve NS equation firstly, and then treat the flow field as stable field, and then only calculate kE equations for the fluctuating variables. Normally, how do you guys do it? Thanks. 

January 15, 2014, 17:25 

#2 
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Join Date: Jun 2011
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Hi David,
I would be curious to know how you will handle the clousure problem. AFAIK u need to related the unkonw Reynolds stresses to the known mean flow variabes through the turbulent transport equations. The latest can be 1eq. models, 2eq. model or second clousures. U must end up with: Full NS eq.  Averaged NS eq. = eq. for fluctuations. Regards, 

January 16, 2014, 12:46 

#3 
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Martin Hegedus
Join Date: Feb 2011
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In general, the turbulence model is decoupled from the N.S. equations during the solution process.


January 17, 2014, 00:51 

#4 
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Join Date: Oct 2012
Location: IITHyderabad, India
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Hi!!
This is how I had implemented ke model 1. Initialize some velocity field. 2. Calculate k. 3. Calculate epsilon 4. Calculate turb viscosity. 5. solve NS to get new velocity field. 6. if velocity < stopping criteria, goto 2, else stop. If you have any doubts, please reply back!! 

January 17, 2014, 01:38 

#5 
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Martin Hegedus
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A note, from what I understand, the two equation models are finicky about how the convection terms are discritized. The SA model is forgiving, so first order upwind is OK. Also, the two equation implicit methods are a little more tricky, assuming of course that an implicit method is used.


January 17, 2014, 12:45 

#6  
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David
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Quote:
THanks for all. When calculating k and epsilon, what algorithm can I use? for example, if I used SIMPLE for velocity field, do I need do any special treatment for the K and E equations? Thanks. 

January 19, 2014, 01:03 

#7 
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TWB
Join Date: Mar 2009
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Hi, I'm also trying to update my laminar code to turbulent. I'm reading Wilcox's turbulence modeling for CFD. Is there any books or online material which details the steps for a novice to follow?


January 19, 2014, 02:20 

#8  
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Give me some time, and i'll upload a document regarding the same, just remind me once after wednesday Quote:


January 19, 2014, 13:40 

#9  
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David
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