Plot swirl number along length of a tube

Pacca · October 24, 2014, 08:57

Hello everybody,

I'm doing some simulations with CFX of a swirling flow in a tube. After obtaining a solution, i defined in CFD-Post the swirl number as:

Code:

areaInt(Density*(X^2+Y^2)*sqrt(Velocity w^2)*sqrt((Velocity u^2)+(Velocity v^2)))@Plane 2/(maxVal(sqrt(X^2+Y^2))@Plane 2*areaInt(Density*(sqrt(X^2+Y^2))*Velocity w^2)@Plane 2)

where Plane 2 is a plane perpendicular to the axis direction Z
Now I'm trying to plot the variation of this variable along the length of the tube, creating a user defined variable SN. But I don't know how to plot it using different planes from Plane 2, because now if i plot SN I have only the same value along the length.
I searched some tutorial or doc but I can't understand how to do this...
I hope that someone can help me

ghorrocks · October 26, 2014, 05:58

You will probably have to export this from CFX (using file/export and specifying your line as the object and your variable as the output variable) and plot it in something else like excel, matlab, python or whatever you flavour of graphing software is.

Pacca · October 26, 2014, 06:24

Thank you for your answer!
The problem is that the variable SN is defined with the expression i wrote in the first post. In this expression there is the geometrical place @Plane 2, and so also exporting the data gives me only the value at that plane. Instead I want the plane to move along the Z axis to calculate the different values of SN...
I have to create one plane where evaluate the SN for every point of my plot or there is a way to do this automatically?

ghorrocks · October 26, 2014, 06:28

I fear you will have to create a plane at each location. Use a session file to make this easier. You get bonus points if you use a perl script looping structure. I only have a small brain which avoids perl whenever possible so I would just generate a text file which contains the full session file.

Pacca · October 26, 2014, 06:37

I have to admit that I'm new with this kind of stuff, I don't know how to make session files...do you now where I can find some help documents on this topic? Or do you know how to make this tipe of sesion file?
Again, thank you very much!

ghorrocks · October 26, 2014, 16:20

The best way to learn is to open up CFD-Post, and start recording a session file from the top menu. Do the operations you want to repeat and have a look at the text file it generates. Then edit the text file to do what you want and replay it the generate your data.

Pacca · October 27, 2014, 14:42

Thank you very much! I solved my problems

October 24, 2014, 08:57	Plot swirl number along length of a tube	#1
Pacca New Member Join Date: Oct 2014 Posts: 12 Rep Power: 11	Hello everybody, I'm doing some simulations with CFX of a swirling flow in a tube. After obtaining a solution, i defined in CFD-Post the swirl number as: Code: areaInt(Density(X^2+Y^2)sqrt(Velocity w^2)sqrt((Velocity u^2)+(Velocity v^2)))@Plane 2/(maxVal(sqrt(X^2+Y^2))@Plane 2areaInt(Density(sqrt(X^2+Y^2))Velocity w^2)@Plane 2) where Plane 2 is a plane perpendicular to the axis direction Z Now I'm trying to plot the variation of this variable along the length of the tube, creating a user defined variable SN. But I don't know how to plot it using different planes from Plane 2, because now if i plot SN I have only the same value along the length. I searched some tutorial or doc but I can't understand how to do this... I hope that someone can help me

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October 26, 2014, 05:58		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You will probably have to export this from CFX (using file/export and specifying your line as the object and your variable as the output variable) and plot it in something else like excel, matlab, python or whatever you flavour of graphing software is.

October 26, 2014, 06:24		#3
Pacca New Member Join Date: Oct 2014 Posts: 12 Rep Power: 11	Thank you for your answer! The problem is that the variable SN is defined with the expression i wrote in the first post. In this expression there is the geometrical place @Plane 2, and so also exporting the data gives me only the value at that plane. Instead I want the plane to move along the Z axis to calculate the different values of SN... I have to create one plane where evaluate the SN for every point of my plot or there is a way to do this automatically?

October 26, 2014, 06:28		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	I fear you will have to create a plane at each location. Use a session file to make this easier. You get bonus points if you use a perl script looping structure. I only have a small brain which avoids perl whenever possible so I would just generate a text file which contains the full session file.

October 26, 2014, 06:37		#5
Pacca New Member Join Date: Oct 2014 Posts: 12 Rep Power: 11	I have to admit that I'm new with this kind of stuff, I don't know how to make session files...do you now where I can find some help documents on this topic? Or do you know how to make this tipe of sesion file? Again, thank you very much!

October 26, 2014, 16:20		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	The best way to learn is to open up CFD-Post, and start recording a session file from the top menu. Do the operations you want to repeat and have a look at the text file it generates. Then edit the text file to do what you want and replay it the generate your data.

October 27, 2014, 14:42		#7
Pacca New Member Join Date: Oct 2014 Posts: 12 Rep Power: 11	Thank you very much! I solved my problems