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

Help to plot variation of absolute pressure Vs time in transient problem

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 21, 2012, 07:04
Question Help to plot variation of absolute pressure Vs time in transient problem
  #1
New Member
 
Chirag
Join Date: Feb 2012
Posts: 18
Rep Power: 5
Chirag2302 is on a distinguished road
Hello,

I am analyzing a oscillatory flow in channel. I am using 2D,Pressure based solver, Transient model. I want output at a one point.

I had defined a surface monitor at that particular point for Area weighted absolute pressure Vs flow time....I think it is right but my output is as shown in fig.

Can anyone help me to correct this???????


Thanks......
Attached Images
File Type: jpg Absolute pressure Vs time at point after stack.jpg (81.9 KB, 25 views)
Chirag2302 is offline   Reply With Quote

Old   April 21, 2012, 17:27
Default
  #2
Member
 
banty
Join Date: Mar 2012
Posts: 52
Rep Power: 5
banty is on a distinguished road
U are getting constant pressure (101325 Pa) but the graph looks strange. should be parallel to time axis ?
banty is offline   Reply With Quote

Old   April 21, 2012, 17:41
Default
  #3
Senior Member
 
Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 605
Rep Power: 12
LuckyTran is on a distinguished road
Quote:
Originally Posted by Chirag2302 View Post
Hello,

I am analyzing a oscillatory flow in channel. I am using 2D,Pressure based solver, Transient model. I want output at a one point.

I had defined a surface monitor at that particular point for Area weighted absolute pressure Vs flow time....I think it is right but my output is as shown in fig.

Can anyone help me to correct this???????


Thanks......
Use one of the two: vertex minimum, or maximum. Do not use vertex average, and also do not any of the weighted averages. If you use vertex minimum/maximum it will simply output the min/max of all values. If your monitor is a single point it will output only that point. If you use one of the weighted averages it will start to compute the quantities (and introduce small errors, such as the vertex area). It is simply better to use one of the vertex options.

Other than that, it seems (at least your plot) is outputting correctly. If it was a transient simulation I would expect stronger pressure oscillations, but it seems your pressure is fairly constant with small oscillations (these are probably introduced by the averaging scheme). You are also plotting against time-step so it may be hard to judge.
LuckyTran is offline   Reply With Quote

Old   April 21, 2012, 23:54
Default Thanks
  #4
New Member
 
Chirag
Join Date: Feb 2012
Posts: 18
Rep Power: 5
Chirag2302 is on a distinguished road
Quote:
Originally Posted by banty View Post
U are getting constant pressure (101325 Pa) but the graph looks strange. should be parallel to time axis ?
Thank you....Banty
Chirag2302 is offline   Reply With Quote

Old   April 22, 2012, 00:01
Default
  #5
New Member
 
Chirag
Join Date: Feb 2012
Posts: 18
Rep Power: 5
Chirag2302 is on a distinguished road
Quote:
Originally Posted by LuckyTran View Post
Use one of the two: vertex minimum, or maximum. Do not use vertex average, and also do not any of the weighted averages. If you use vertex minimum/maximum it will simply output the min/max of all values. If your monitor is a single point it will output only that point. If you use one of the weighted averages it will start to compute the quantities (and introduce small errors, such as the vertex area). It is simply better to use one of the vertex options.

Other than that, it seems (at least your plot) is outputting correctly. If it was a transient simulation I would expect stronger pressure oscillations, but it seems your pressure is fairly constant with small oscillations (these are probably introduced by the averaging scheme). You are also plotting against time-step so it may be hard to judge.
Thank you.......LuckyTran

I had also monitored with respect to flow time but the output is same. and you are right strong pressure oscillation is expected with amplitude approximately near to 7500 to 8500 Pascals with oscillation frequency of 614 Hz.
Chirag2302 is offline   Reply With Quote

Reply

Tags
plot pressure vs time

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
Moving mesh Niklas Wikstrom (Wikstrom) OpenFOAM Running, Solving & CFD 122 June 15, 2014 06:20
calculation diverge after continue to run zhajingjing OpenFOAM 0 April 28, 2010 04:35
Could anybody help me see this error and give help liugx212 OpenFOAM Running, Solving & CFD 3 January 4, 2006 19:07
what the result is negatif pressure at inlet chong chee nan FLUENT 0 December 29, 2001 06:13
unsteady calcs in FLUENT Sanjay Padhiar Main CFD Forum 1 March 31, 1999 12:32


All times are GMT -4. The time now is 13:03.