Problem with the concept of automatic wall treatment

ndabir · March 9, 2010, 17:07

Hi

I am using SST and standard k-omega with fine mesh. does the automatic wall treatment uses the low-Re form of these turbulence models or it uses their high-Re form?
I don't understant the manual that says the automatic wall treatment switches from low-Re to wall function by changinging y+. does it mean that it switches from the low-Re form of the k-omega to its high-Re form?if this is true then why there is not any formulation for low-Re k-omega in the manual cause its formulaion is different from its standard form. In fluent there is a formulation for low-Re k-omega when you active the transitional object.

ghorrocks · March 10, 2010, 06:21

SST by default uses automatic wall functions which can blend from integration to the wall to a wall function approach. This is described in the documentation. And don't forget SST is itself a blending of k-omega and k-e turbulence models.

You don't have automatic wall functions in k-omega models because y+>13 wall functions do not exist.

March 9, 2010, 17:07	Problem with the concept of automatic wall treatment	#1
ndabir Senior Member navid Join Date: Jan 2010 Posts: 110 Rep Power: 16	Hi I am using SST and standard k-omega with fine mesh. does the automatic wall treatment uses the low-Re form of these turbulence models or it uses their high-Re form? I don't understant the manual that says the automatic wall treatment switches from low-Re to wall function by changinging y+. does it mean that it switches from the low-Re form of the k-omega to its high-Re form?if this is true then why there is not any formulation for low-Re k-omega in the manual cause its formulaion is different from its standard form. In fluent there is a formulation for low-Re k-omega when you active the transitional object.

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March 10, 2010, 06:21		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	SST by default uses automatic wall functions which can blend from integration to the wall to a wall function approach. This is described in the documentation. And don't forget SST is itself a blending of k-omega and k-e turbulence models. You don't have automatic wall functions in k-omega models because y+>13 wall functions do not exist.