Specification of wall function, Y+ in CFX

Kishore · June 22, 2010, 05:54

Hi all,
The manual defines but doesnt seem to help in defining wall function or y+.
Can anybody here worked on that, please tell me where do we define/edit that in CFX

Regards,
Kishore

ghorrocks · June 22, 2010, 19:49

It is all discussed in the documentation under wall boundary conditions.

Kishore · June 22, 2010, 22:03

Horrocks, Thanks for your response.
The manual doesn't say where I can specify in the user interface.

If I click over the boundary which is defined as a wall, in the boundary details I can specify the wall influence on the flow or heat transfer.

My objective is to switch off the wall function option to resolve boundary layers or change the y+. I am not able to find that in the user interface and the manual gives the theory and doesn't tell me where I have to do it.

Kindly help!

ghorrocks · June 23, 2010, 08:18

If you use k-e turbulence mode then you have to use wall functions as epsilon is undefined at the wall so you have to do something different to get that under control. If you want to integrate to the wall use a k-w turbulence model. Even better, use the SST turbulence model and it will handle the transition from wall functions to integrating to the wall by itself.

June 22, 2010, 05:54	Specification of wall function, Y+ in CFX	#1
Kishore New Member Kishore Kumar C Join Date: Sep 2009 Location: Bangalore Posts: 12 Rep Power: 16	Hi all, The manual defines but doesnt seem to help in defining wall function or y+. Can anybody here worked on that, please tell me where do we define/edit that in CFX Regards, Kishore

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June 22, 2010, 19:49		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	It is all discussed in the documentation under wall boundary conditions.

June 22, 2010, 22:03		#3
Kishore New Member Kishore Kumar C Join Date: Sep 2009 Location: Bangalore Posts: 12 Rep Power: 16	Horrocks, Thanks for your response. The manual doesn't say where I can specify in the user interface. If I click over the boundary which is defined as a wall, in the boundary details I can specify the wall influence on the flow or heat transfer. My objective is to switch off the wall function option to resolve boundary layers or change the y+. I am not able to find that in the user interface and the manual gives the theory and doesn't tell me where I have to do it. Kindly help!

June 23, 2010, 08:18		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	If you use k-e turbulence mode then you have to use wall functions as epsilon is undefined at the wall so you have to do something different to get that under control. If you want to integrate to the wall use a k-w turbulence model. Even better, use the SST turbulence model and it will handle the transition from wall functions to integrating to the wall by itself.