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Wall treatment - RSM turbulence model

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Old   September 10, 2012, 05:34
Default Wall treatment - RSM turbulence model
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Hi guys,
I'm modelling a cold chamber with Star CCM+ using RSM turbulence model.
With this turbulence model, Star CCM automatically select the high y+ wall treatment because RSM model is more valid when near wall cells are located in the log law region (high y+ value).
However my question is, what's happening when the y+ value falls below the recommanded minimal value (12).
I've read that in Fluent an hybrid wall treatment is available which switch automatically the resolution depending on the y+ value when y+ is above or below 11.225.
Is Star CCM doing the same even if the high y+ wall treatment is selected ?
Thanks,
Djack
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Old   September 12, 2012, 10:51
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Quote:
Originally Posted by djack View Post
I've read that in Fluent an hybrid wall treatment is available which switch automatically the resolution depending on the y+ value when y+ is above or below 11.225.
Is Star CCM doing the same even if the high y+ wall treatment is selected ?
I don't think so. But you might uncheck "Auto-select recommended models" and choose "Linear Pressure Strain Two-Layer" instead of "Linear Pressure Strain". Then you will have a All-Y+ Wall Treatment available. Please have a look in the user guide, there's an explanation what the All-Y+ wall treatment does:

Quote:
The All y+ Wall Treatment makes no assumption about how well the viscous sublayer is resolved. By using a blended wall law to estimate shear stress, the result will be similar to the Low y+ wall treatment if the mesh is fine enough. If the mesh is coarse enough (y+ > 30), the wall law is equivalent to a logarithmic profile.
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