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Turbulence models and boundary layer

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Old   March 14, 2006, 02:42
Default Turbulence models and boundary layer
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Stanislav Kraev
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Hi

FLUENT documentation says that for standard wall functions you should create model with Yplus in the range 30-60. How can I estimate the error for my case if Yplus is much smaller? I realized that there are a lot of areas with Yplus about 1-5. Is the result totally incorrect? And what should I do if there are a wide range of velocities in my model (0.1-5 m/s in stagnation zones and up to 40 m/s in other zones)? What turbulence model should I use? I don't think that I should greately coarse mesh in stagnation zones because I will get very big cells and geometry features will not catched. Am I right?

Thanks a lot for any help.
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Old   March 14, 2006, 06:55
Default Re: Turbulence models and boundary layer
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Razvan
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Use Enhanced Wall Treatment (EWT), it is supposed to minimise error when y+ is around 11, and extends validity of wall functions to all range of possible y+ values. BUT this is advisable to do only if mean y+ is towards 1, not 30. In your case, it is better to make a y+ adaption to get it to 1 (you say that coarsening the grid would be inappropriate), or remake the grid near the body. Then simply choose a low-Re model (like S-A or k-w [with "transitional flow" option activated]), or a high-Re model with EWT (k-e or RSM).

Razvan
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