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

Pressure outlet

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 12, 2006, 00:01
Default Pressure outlet
  #1
Vidya
Guest
 
Posts: n/a
Hi,

I want to retain my outlet Boundary Condition to be specified as being at atmospheric pressure. For this, I chose the face that is to be the outlet, went to BC in Fluent, selected the PRESSURE OUTLET option, and just selected OK to whatever the default was. Isn't the default set to atmospheric pressure? then why does Fluent give error messages?

Since the deafult gage pressure is zero, the pressure is atmospheric. So what could be the problem?

Thanks.
  Reply With Quote

Old   July 12, 2006, 14:37
Default Re: Pressure outlet
  #2
Vivek
Guest
 
Posts: n/a
There shouldn't be any problem. What error message did u get?
  Reply With Quote

Old   July 12, 2006, 15:11
Default Re: Pressure outlet
  #3
Vidya
Guest
 
Posts: n/a
It just gave a value of zero velocity at every point in the flow domain, which is absolutely meaningless. Also, all other parameters like pressure etc were either zero, when it actually shouldn't be, or sometimes goes to zero, which is again absurd.

Will specifying pressures at both the inlet and outlet help solve the problem?

Thanks
  Reply With Quote

Old   July 12, 2006, 16:08
Default Re: Pressure outlet
  #4
Vivek
Guest
 
Posts: n/a
whats ur inlet boundary condition now? what problem are you trying to solve?
  Reply With Quote

Old   July 12, 2006, 18:10
Default Re: Pressure outlet
  #5
Vidya Raja
Guest
 
Posts: n/a
I gave a steady input velocity of 0.175 m/s at the inlet. I want to retain the outlet at atmospheric pressure. The flow is laminar, and I'm trying to model blood flow.

Is it possible to specify pressure BCs at both inlet and outlet? Then the inlet pressure is very small..... about 1.5 mm Hg. That's why I want to use the velocity at the inlet. I also have to run the case using an unsteady velocity.

  Reply With Quote

Old   July 13, 2006, 13:00
Default Re: Pressure outlet
  #6
Vivek
Guest
 
Posts: n/a
You could do it either way. There shouldn't be any problem at all. Just make sure if there is an internal suface which you forgot to change from the default wall boundary condition. Its typically the reason for zero velocities
  Reply With Quote

Old   July 13, 2006, 14:20
Default Re: Pressure outlet
  #7
Vidya Raja
Guest
 
Posts: n/a
I made that change, but the residuals never converge. However, the trends for all the residuals (continuity, x,y,z velocities) appears to be the same. Even after 17,000 iterations, the solution doesn't converge.

What could be wrong now?

Thanks, Vidya

  Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Problems in pressure when using mass flow rate outlet rafiktharwat CFX 11 January 2, 2014 18:21
pressure oscillation near pressure outlet boundary kino Main CFD Forum 5 April 13, 2011 12:03
Pressure Outlet setting CoG STAR-CCM+ 4 June 9, 2010 22:47
what actually is the 'zero pressure outlet b. c.' hwe001 CFX 4 June 7, 2010 16:22
Backflow occuring at a pressure outlet? Dave FLUENT 1 August 12, 2004 18:39


All times are GMT -4. The time now is 19:24.