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K-omega SST grid resolution

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Old   October 17, 2006, 03:05
Default K-omega SST grid resolution
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efb
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I'm doing unsteady simulation on 2d airfoil (Rey number 800000)with pulsed mass injection through slot using k-omega 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 k-eps 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
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Old   October 17, 2006, 04:46
Default Re: K-omega SST grid resolution
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sam
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you should also read abt how many should be in the viscous sublayer.
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Old   October 17, 2006, 09:33
Default Re: K-omega SST grid resolution
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sam
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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 wall-function mesh typically requires about 10 cells in the boundary layer whereas a resolved low-Re mesh requires about 40 cells in the boundary layer.

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Old   October 17, 2006, 09:37
Default Re: K-omega SST grid resolution
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efb
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thank you sam..I will try bye
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Old   October 17, 2006, 09:42
Default Re: K-omega SST grid resolution
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sam
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u r welcome
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Old   October 17, 2006, 10:36
Default Re: K-omega SST grid resolution
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Ralf Schmidt
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Hi!

There are some information in the fluent manual, summarized in the wiki:

http://www.cfd-online.com/Wiki/Near-...k-omega_models

Hope, it helps

Ralf
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Old   October 17, 2006, 13:08
Default Re: K-omega SST grid resolution_an important issue
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sam
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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.
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Old   October 18, 2006, 04:41
Default Re: K-omega SST / Interference
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Amr
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I apologize for this off-track interference. It is an issue related to the k-w 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 k-w (Shear Stress Transport) model account for turbulent generation due to buoyancy?. In the fluent manual, the two-equation set for k and w do not show the term that accounts for buoyancy effect, unlike what you see in k-epsilon equations. While not sure about this, I understood from the manual that when I activate the k-w model, the software applies the k-w model for low Re regions and applies the k-e model in the free stream with buoyancy effect. Is this correct?.

Thanks in advance for your help.

Cheers Amr

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Old   June 15, 2012, 04:19
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I'm also interested about Amr's question
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