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

high pressure boundary condition

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 10, 2012, 14:25
Default high pressure boundary condition
  #1
New Member
 
Join Date: Apr 2012
Posts: 3
Rep Power: 5
fragzilla is on a distinguished road
Hello, im currently working on simulating some channels in an hydralic pump, but I got some problems with the boundary conditions due the high pressure.

The problem consist of a 90 degree bending pipe, I've been trying to use a normal velocity around 20m/s for the inlet boundary condition and for the outlet i've been trying diffrent kind of pressure conditions, with 'relative pressure' equal set to 220 bar. The domains referense pressure is set to 1 atm.
the reasons of my problem could be that I use the standard water model instead of oil?
and another strange thing is that the models works fine every time i run it with relative pressure equal to 0...

The thing im investigating is the pressure loss in the channel for a flow of 20m/s and a exiting pressure of 220bar
fragzilla is offline   Reply With Quote

Old   September 10, 2012, 18:27
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,931
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Is the fluid incompressible? Is the exit boundary pressure the only place pressure is set at?
ghorrocks is offline   Reply With Quote

Old   September 13, 2012, 15:38
Default
  #3
New Member
 
Join Date: Apr 2012
Posts: 3
Rep Power: 5
fragzilla is on a distinguished road
I want the outlet to have the pressure of 220 Bar, its supposed to be hydralic oil,

I solved the problem with outlet and average static pressure, and did use upwind and then high resolution and got a solution

Thanks anyways ghorrocks
fragzilla is offline   Reply With Quote

Old   September 13, 2012, 19:22
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,931
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
You have not answered my questions. Is the flow incompressible? Is the exit the only place the pressure is set at?

If this is the only place the pressure is set then you would be better off to use a boundary condition pressure of 0 bar, and a reference pressure of 220bar. This will reduce round off errors.
ghorrocks is offline   Reply With Quote

Old   September 14, 2012, 01:13
Default
  #5
New Member
 
Join Date: Apr 2012
Posts: 3
Rep Power: 5
fragzilla is on a distinguished road
yes, the flow is assumed to be incompressible and i've only used pressure boundary conditions at the end. the case i basicly to what the pressure need to be in start to get 220bar out,
fragzilla is offline   Reply With Quote

Old   September 14, 2012, 02:40
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,931
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
In that case set the reference pressure to 220 bar and the outlet pressure to 0 bar. This will reduce round off errors and make convergence easier.
ghorrocks is offline   Reply With Quote

Reply

Tags
boundary conditions

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 boundary condition C-H Kuo Main CFD Forum 10 August 26, 2015 07:45
pressure outlet boundary condition liladhar STAR-CCM+ 6 May 12, 2012 05:09
Pressure Boundary condition abishek FLUENT 1 July 28, 2008 08:14
Boundary condition in pressure equation Paolo Lampitella FLUENT 0 February 21, 2008 07:30
Question about pressure inlet boundary condition. Alina FLUENT 1 November 30, 2007 08:39


All times are GMT -4. The time now is 15:38.