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YPlus value -- CFX 5.7

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Old   December 5, 2004, 16:49
Default YPlus value -- CFX 5.7
  #1
NeedHelp
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I am doing flow through wall problems, I choose SST model for it, but SST model is good for Yplus value less than 2, the Yplus value I got is always bigger than 2, min I got is around 3, can I still use SST model?

Also sometimes I use more elements for mesh, but Yplus value got bigger, can somebody give some suggestions on Yplus value vs. mesh? and how it affect model selection and results?

Thanks.
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Old   December 5, 2004, 17:39
Default Re: YPlus value -- CFX 5.7
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Glenn Horrocks
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Hi,

The SST model with automatic wall functions is fine for y+ up to several hundred. Of course it will be in wall function mode rather than integrate to the wall mode for these large y+ and that may or may not be appropriate for you simulation depending on what you are doing.

Glenn Horrocks
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Old   December 6, 2004, 07:25
Default Re: YPlus value -- CFX 5.7
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James Date
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Yep,

Like Glenn said, the SST will just run using the standard wall function approach in the Y+ > 1 range. Your best bet is to go back and reduce your first cell size and re-run the simulation and check the Y+. I usually do one or two Y+ scoping runs (solving for 10 or so iterations) to get a feel for the Y+, subsequently modifying the mesh density near the wall to get the correct Y+.

Regards

James
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Old   December 7, 2004, 21:46
Default Re: YPlus value -- CFX 5.7
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Susn
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Hi, I am puzzled in y+, Could you tell me the rang of y+ when using different models? Susn
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