Wall Functions & Turbulence Models Query [y plus ranges]

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 August 14, 2018, 16:37 Wall Functions & Turbulence Models Query [y plus ranges] #1 New Member   Join Date: Oct 2017 Posts: 25 Rep Power: 7 Hi I'm trying to understand the wall functions and turbulence models and the requirements to satisfy each mathematical model via the mesh. Please correct me if I'm wrong below. Standard wall functions y+ range 30 < 300 Enhanced wall treatment, Fluent manual doesn't appear to be clear on this issue, some say < 1 others say <10. For k-w models y+ < 1 for all. Thanks. TheMightySpartan

 August 14, 2018, 16:54 #2 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,146 Rep Power: 61 Standard wall functions can certainly be used in the y+<10 range. Standard wall functions have a low reynolds number treatment. What's special about enhanced wall functions, is the enhanced part. Omega models are designed for low y+, but they can tolerate (they use wall functions) for high y+ meshes. Note that k-w SST model is a blended k-e and k-w model that tolerates high and low y+ meshes. y+ < 10 or y+ < 1 is a matter of a lot of personal preference and experience. The point is to be low. The demarcation between viscous sublayer <5 versus linear region <10 only confounds the issue even more. If it matters to you, then do a grid sensitivity study. What's more important than the wall y+ is the total # of grid points you have across the boundary layer and this is not captured by simply plotting y+.

 August 14, 2018, 17:02 #3 New Member   Join Date: Oct 2017 Posts: 25 Rep Power: 7 So I should forget about y+ and do mesh sensitivity study?

 August 15, 2018, 04:57 #4 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,146 Rep Power: 61 You should always do a mesh sensitivity study. Especially if you ever plan on publishing anything.

 August 18, 2018, 03:48 #5 New Member   Join Date: Oct 2017 Posts: 25 Rep Power: 7 I understand you are talking about the greater mesh region but there must be some kind of rule book regarding wall functions/turbulence model and y+ right?

 Tags turbulence models, wall functions, y plus ranges