Fluctuating components on CFD-post

Marcoroccia · January 8, 2016, 12:01

Hello, i'm new in this forum

I would like to ask you a question. I need to know how to calculate the fluctuating components of trasversal and streamwise velocity in my BSL-RSM simulation in CFX. The problem is a flow past a rectangular cylinder. In particular I want to extract the values of u' and v' on a plane downstream the cylinder. In attached the picture of my problem.

thank you so much

ghorrocks · January 10, 2016, 01:23

You can get u' from the Reynolds stresses. Or are you asking how to post process it? Just put a plane across the flow at the required location and you can use that plane to display variables or extract data.

Marcoroccia · January 10, 2016, 04:08

Thank you for the aswer. I created three planes in which calculate the u' v'. But, in particular, what is the function in tab espressions that i have to use? ......?.....(reynolds stress u)@plane
The same problem with the search of y plus around the square section : ......?.....(y+)@wallsection

ghorrocks · January 10, 2016, 16:56

You will have to define your own variable to calculate it. It is not a variable in CFX by default.

y+ only exists at the walls. If your plane goes through the middle of the domain there will be no value for it in the middle of the flow and it will only exist at the walls.

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January 10, 2016, 01:23		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,708 Rep Power: 143	You can get u' from the Reynolds stresses. Or are you asking how to post process it? Just put a plane across the flow at the required location and you can use that plane to display variables or extract data.

January 10, 2016, 04:08		#3
Marcoroccia New Member Marchetto Join Date: Jan 2016 Posts: 2 Rep Power: 0	Thank you for the aswer. I created three planes in which calculate the u' v'. But, in particular, what is the function in tab espressions that i have to use? ......?.....(reynolds stress u)@plane The same problem with the search of y plus around the square section : ......?.....(y+)@wallsection

January 10, 2016, 16:56		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,708 Rep Power: 143	You will have to define your own variable to calculate it. It is not a variable in CFX by default. y+ only exists at the walls. If your plane goes through the middle of the domain there will be no value for it in the middle of the flow and it will only exist at the walls.