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k-omega-SST model (OF 1.6) - turbulent flat plate

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Old   February 5, 2011, 02:41
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Travis Carrigan
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To cboss:

Do you think you could post your setup, 0/nut, 0/k, 0/omega, fvSchemes, fvSolution, etc...?

I've been trying to simulate turbulent flow over a flat plate in OpenFOAM-1.6-ext for both a resolved grid with a y+=1 and an unresolved grid with a y+=60. I'm also using the kOmegaSST model with and without wall functions to handle both grids.

The problem I'm having is that when running the resolved grid using the kOmegaSST model, I'm slightly underpredicting the skin friction by just a few percent. However, when running the unresolved grid with wall functions for the kOmegaSST model, I'm severly underpredicting the skin friction.

Looking at your images, the behavior I'm seeing for the unresolved grid is similar to the behavior of the y+=30 grid you plotted in your third image when you were comparing the results of cases without using wall functions. This leads me to believe that either I'm not implementing the wall functions correctly, or the wall functions aren't being utilized during the simulation at all.

Thinking this was an issue with 1.6-ext, I installed OpenCFDs 1.6 version from mid February 2010, about the time of your original post. I reran the case using this version and observed the same behavior. So it seems it might be my problem.

Any help would be much appreciated.
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Old   February 5, 2011, 07:46
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Hi,

nice, that this post is still recognized.

To your questions: The problem is, that I haven't been working with OpenFOAM for a long time, and that I don't have access to the done simulations. And it's quite complicated to get into it again, if you have neither a version of OF, nor any data. So I'm afraid, that I cannot give you a good advice.
Perhaps someone else can help.

Regards
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Old   February 5, 2011, 10:50
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Maruthamuthu Venkatraman
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Hi,
Your answers are kept in Turbulence modelling for CFD by Wilcox . Just have a look at it how to set omega values at the nearwall cells. In general refer Ercoftac best pracise guidelines recommended BC's for external flows.

Good Luck. I dont think schemes will make big difference in this case.

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Old   November 13, 2011, 02:28
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Sijal Ahmed Memon (turboenginner@gmail.com)
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Quote:
Originally Posted by cboss View Post
Nick,

(3) Yes, I set k as fixedValue=0.
In the original paper it is mentioned as flux = zero
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