# Question about extracting volume averaged pressure value

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November 28, 2012, 03:56
Question about extracting volume averaged pressure value
#1
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Meimei Wang
Join Date: Jul 2012
Posts: 494
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Hi,

May I ask, in cfx-post, how to extract the volume averaged pressure value of a cylinder shape volume(like in the attached picture) from my fluid domain?

Shall I still go 'Insert -> Location - Volume'?

Thank you very much!
Attached Images
 untitled.bmp (67.6 KB, 9 views)
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Best regards,
Meimei

Last edited by Anna Tian; November 29, 2012 at 04:25.

 November 28, 2012, 07:10 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,808 Rep Power: 107 The image was not attached.

November 29, 2012, 04:25
#3
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Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 9
Quote:
 Originally Posted by ghorrocks The image was not attached.
The picture is already attached. It is just a small cylinder. And I only need to know the averaged pressure value in this volume. Thanks!
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Best regards,
Meimei

 November 29, 2012, 05:03 #4 Senior Member   Lance Join Date: Mar 2009 Posts: 610 Rep Power: 14 A search in the manual on volume average would give you: volumeAve()@ In your case it would be something like volumeAve(Pressure)@cylinder

November 29, 2012, 10:32
#5
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Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 9
Quote:
 Originally Posted by Lance A search in the manual on volume average would give you: volumeAve()@ In your case it would be something like volumeAve(Pressure)@cylinder
The problem is my fluid domain is not cylindrical. I need to put a cylinder there by myself so that I can extract only the value inside the cylinder. But how to put a cylinder into my fluid domain?
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Meimei

 November 29, 2012, 12:27 #6 Senior Member   Bruno Join Date: Mar 2009 Location: Brazil Posts: 279 Rep Power: 14 1. Take the equation of your cylinder, such as2. Create an expression for the radiusradius = sqrt(x^2 + y^2) 3. Create a other expressions to check whether you're inside the cylinder:insideCylinderZdir = if(radius < , yourvariable, 0)insideCylinder = if( zCylinderInf < z && z < zCylinderTop, insideCylinderZdir, 0 )where 'zCylinderInf' and 'zCylinderTop' are the extreme positions of your cylinder in it's axial direction. 4. Create an expression to average 'insideCylinder' over your entire domain:cylAve = volumeAve(insideCylinder)@domainThat should do it. Cheers.

November 29, 2012, 12:47
#7
Senior Member

Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 9
Quote:
 Originally Posted by brunoc 1. Take the equation of your cylinder, such as2. Create an expression for the radiusradius = sqrt(x^2 + y^2)3. Create a other expressions to check whether you're inside the cylinder:insideCylinderZdir = if(radius < , yourvariable, 0)insideCylinder = if( zCylinderInf < z && z < zCylinderTop, insideCylinderZdir, 0 )where 'zCylinderInf' and 'zCylinderTop' are the extreme positions of your cylinder in it's axial direction. 4. Create an expression to average 'insideCylinder' over your entire domain:cylAve = volumeAve(insideCylinder)@domainThat should do it. Cheers.

Where should I add these expressions?
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Meimei

 November 29, 2012, 12:55 #8 Senior Member   Bruno Join Date: Mar 2009 Location: Brazil Posts: 279 Rep Power: 14 They should be added as CEL Expressions. CFX has lots of tutorials that address how to use them.

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