How to create additional variable for the eddy viscosity ratio

ttu004 · October 24, 2013, 21:16

Hi there

Can anyone please tell me how to create an additional variable for the eddy viscosity ratio in CFX-pre so that I can use it in CFX-post for boundary layer flow separation analysis.

Cheers
Tom

ghorrocks · October 24, 2013, 21:46

In CFD-Post, create a new variable (the "x" button) and give it the expression Eddy Viscosity/Dynamic Viscosity.

Pretty simple.

ttu004 · October 24, 2013, 23:38

Got it

Thanks Glenn

keeper · October 30, 2013, 03:36

may I ask what does it really express and how can I use it for cases?

Thank you

ghorrocks · October 30, 2013, 05:00

It tells you how much of the viscosity in the model comes from the turbulence model and how much comes from the laminar viscosity. As the model becomes highly turbulent this ratio gets large. For some applications a ratio of 1 is defined as the transition to turbulence (but in my opinion it is not a very good definition

)

October 24, 2013, 21:16	How to create additional variable for the eddy viscosity ratio	#1
ttu004 New Member Tom Join Date: Oct 2013 Location: Auckland, New Zealand Posts: 24 Rep Power: 12	Hi there Can anyone please tell me how to create an additional variable for the eddy viscosity ratio in CFX-pre so that I can use it in CFX-post for boundary layer flow separation analysis. Cheers Tom

October 30, 2013, 05:00		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,692 Rep Power: 143	It tells you how much of the viscosity in the model comes from the turbulence model and how much comes from the laminar viscosity. As the model becomes highly turbulent this ratio gets large. For some applications a ratio of 1 is defined as the transition to turbulence (but in my opinion it is not a very good definition ) keeper and Saeef like this.

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October 24, 2013, 21:46		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,692 Rep Power: 143	In CFD-Post, create a new variable (the "x" button) and give it the expression Eddy Viscosity/Dynamic Viscosity. Pretty simple.

October 24, 2013, 23:38		#3
ttu004 New Member Tom Join Date: Oct 2013 Location: Auckland, New Zealand Posts: 24 Rep Power: 12	Got it Thanks Glenn

October 30, 2013, 03:36		#4
keeper Senior Member Join Date: Jul 2010 Posts: 152 Rep Power: 15	may I ask what does it really express and how can I use it for cases? Thank you