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October 17, 2006, 03:05 
Komega SST grid resolution

#1 
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I'm doing unsteady simulation on 2d airfoil (Rey number 800000)with pulsed mass injection through slot using komega SST turbulence model. I have read that to correctly use this model yplus should be less than 0.1, but I thought that the grid wall resolution was similar to keps with enhanced wall treatment that requires yplus near or less 1.0 but not necessarily less than 0.1.. I'd like to know which is the thuth..
thank you bye 

October 17, 2006, 04:46 
Re: Komega SST grid resolution

#2 
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you should also read abt how many should be in the viscous sublayer.


October 17, 2006, 09:33 
Re: Komega SST grid resolution

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this is frm CFDwiki
Boundary layer mesh For design iteration type of simulations where, a wall function approach is sufficient, y+ for the first cell should be somewhere between 30 and 300. For more accurate simulations with resolved boundary layers the mesh should have a y+ for the first cell which is below 1. A good rule of thumb is to use a growth ratio in the boundary layer of 1.2  1.25. If you are uncertain of which wall distance to mesh with you can use a y+ estimation tool to estitmate the distance needed to obtain the desired y+. As a rule of thumb a wallfunction mesh typically requires about 10 cells in the boundary layer whereas a resolved lowRe mesh requires about 40 cells in the boundary layer. 

October 17, 2006, 09:37 
Re: Komega SST grid resolution

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thank you sam..I will try bye


October 17, 2006, 09:42 
Re: Komega SST grid resolution

#5 
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u r welcome


October 17, 2006, 10:36 
Re: Komega SST grid resolution

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Hi!
There are some information in the fluent manual, summarized in the wiki: http://www.cfdonline.com/Wiki/Near...komega_models Hope, it helps Ralf 

October 17, 2006, 13:08 
Re: Komega SST grid resolution_an important issue

#7 
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you should not confuse wall y plus with grid indepdent solution . both are different. For example refer to peric book last chapter on accurcy of solution.


October 18, 2006, 04:41 
Re: Komega SST / Interference

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I apologize for this offtrack interference. It is an issue related to the kw SST model, but I have not been successful to resolve it.
Need to ask you a question regarding a turbulent natural convection scenario inside a large hall. Now, the simple question is: Does the kw (Shear Stress Transport) model account for turbulent generation due to buoyancy?. In the fluent manual, the twoequation set for k and w do not show the term that accounts for buoyancy effect, unlike what you see in kepsilon equations. While not sure about this, I understood from the manual that when I activate the kw model, the software applies the kw model for low Re regions and applies the ke model in the free stream with buoyancy effect. Is this correct?. Thanks in advance for your help. Cheers Amr 

June 15, 2012, 04:19 

#9 
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Flavio
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Location: Brescia, Italy
Posts: 181
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I'm also interested about Amr's question


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