CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > CFX

Question about extracting volume averaged pressure value

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   November 28, 2012, 03:56
Question Question about extracting volume averaged pressure value
  #1
Senior Member
 
Anna Tian's Avatar
 
Meimei Wang
Join Date: Jul 2012
Posts: 473
Rep Power: 6
Anna Tian is on a distinguished road
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
File Type: bmp untitled.bmp (67.6 KB, 7 views)
__________________
Best regards,
Meimei

Last edited by Anna Tian; November 29, 2012 at 04:25.
Anna Tian is offline   Reply With Quote

Old   November 28, 2012, 07:10
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,665
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
The image was not attached.
ghorrocks is offline   Reply With Quote

Old   November 29, 2012, 04:25
Default
  #3
Senior Member
 
Anna Tian's Avatar
 
Meimei Wang
Join Date: Jul 2012
Posts: 473
Rep Power: 6
Anna Tian is on a distinguished road
Quote:
Originally Posted by ghorrocks View Post
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!
__________________
Best regards,
Meimei
Anna Tian is offline   Reply With Quote

Old   November 29, 2012, 05:03
Default
  #4
Senior Member
 
Lance
Join Date: Mar 2009
Posts: 522
Rep Power: 11
Lance is on a distinguished road
A search in the manual on volume average would give you: volumeAve(<var|Expression>)@<Location>

In your case it would be something like volumeAve(Pressure)@cylinder
Lance is offline   Reply With Quote

Old   November 29, 2012, 10:32
Default
  #5
Senior Member
 
Anna Tian's Avatar
 
Meimei Wang
Join Date: Jul 2012
Posts: 473
Rep Power: 6
Anna Tian is on a distinguished road
Quote:
Originally Posted by Lance View Post
A search in the manual on volume average would give you: volumeAve(<var|Expression>)@<Location>

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?
__________________
Best regards,
Meimei
Anna Tian is offline   Reply With Quote

Old   November 29, 2012, 12:27
Default
  #6
Senior Member
 
Bruno
Join Date: Mar 2009
Location: Brazil
Posts: 236
Rep Power: 12
brunoc is on a distinguished road
1. Take the equation of your cylinder, such as
x^2 + y^2 = r^2
2. Create an expression for the radius
radius = sqrt(x^2 + y^2)

3. Create a other expressions to check whether you're inside the cylinder:
insideCylinderZdir = if(radius < r, 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)@domain
That should do it.

Cheers.
brunoc is offline   Reply With Quote

Old   November 29, 2012, 12:47
Default
  #7
Senior Member
 
Anna Tian's Avatar
 
Meimei Wang
Join Date: Jul 2012
Posts: 473
Rep Power: 6
Anna Tian is on a distinguished road
Quote:
Originally Posted by brunoc View Post
1. Take the equation of your cylinder, such as
x^2 + y^2 = r^2
2. Create an expression for the radius
radius = sqrt(x^2 + y^2)
3. Create a other expressions to check whether you're inside the cylinder:
insideCylinderZdir = if(radius < r, 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)@domain
That should do it.

Cheers.

Where should I add these expressions?
__________________
Best regards,
Meimei
Anna Tian is offline   Reply With Quote

Old   November 29, 2012, 12:55
Default
  #8
Senior Member
 
Bruno
Join Date: Mar 2009
Location: Brazil
Posts: 236
Rep Power: 12
brunoc is on a distinguished road
They should be added as CEL Expressions. CFX has lots of tutorials that address how to use them.
brunoc is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pressure Outlet Guage pressure Mohsin FLUENT 34 January 12, 2012 06:45
mass flow in is not equal to mass flow out saii CFX 2 September 18, 2009 08:07
On the damBreak4phaseFine cases paean OpenFOAM Running, Solving & CFD 0 November 14, 2008 22:14
what the result is negatif pressure at inlet chong chee nan FLUENT 0 December 29, 2001 06:13
Hydrostatic pressure in 2-phase flow modeling (long) DS & HB Main CFD Forum 0 January 8, 2000 16:00


All times are GMT -4. The time now is 00:09.