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

Outlet Boundary Condition

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

Reply
 
LinkBack Thread Tools Display Modes
Old   December 30, 2001, 12:41
Default Outlet Boundary Condition
  #1
Arash
Guest
 
Posts: n/a
i want to know in defining at oulet boundary condition which parameter must be defined if we know nothing about it. i use finite volume simple method. thanks arash
  Reply With Quote

Old   December 31, 2001, 09:32
Default Re: Outlet Boundary Condition
  #2
Peter
Guest
 
Posts: n/a
If you are running incompressible flow, you don't need to prescribe a pressure profile at the outlet. Usually one specifies that velocities and pressure do not vary in streamwise direction, du/dx=dv/dx=dp/dx=0. If you are using staggered structured mesh, this can be easily implemented in your momentum equation system by adding the term where the velocity is known to the coefficient vector. For the pressure correction equation, no information for the correction term is needed in the boundary, so the corresponding matrix coefficient is equal to zero. Check the book of Patankar for details: Numerical Heat Transfer and Fluid Flow. Page 129.
  Reply With Quote

Old   December 31, 2001, 13:56
Default Re: Outlet Boundary Condition
  #3
John
Guest
 
Posts: n/a
dp/dx ca not be zero - just look at simple channel or pipe flow where dp/dx is constant even at outlet boundary
  Reply With Quote

Old   January 1, 2002, 20:41
Default Re: Outlet Boundary Condition
  #4
Thomas P. Abraham
Guest
 
Posts: n/a
Hello Arash,

You could apply a constant pressure at the outlet. This boundary condition holds good in the region where the flow is fully developed. So, you need to make sure that there is no recirculation in the region where you intend to apply this constant pressure boundary condition.

Even in the fully developed regime, dp/dx is not zero but a constant. Static pressure continues to go down as the flow tries to overcome the viscous forces.

Thanks,

Thomas
  Reply With Quote

Old   January 4, 2002, 09:41
Default Re: Outlet Boundary Condition
  #5
Steven Jachec
Guest
 
Posts: n/a
In modeling shallow water waves in the marine environment, there are times when one does not know the pressure head nor the velocity at an open (unforced) bonundary. In these cases, I use a radiating BC that allows the solutions to be determined on the boundary, as well as allows the waves (including flow) to propagate out of the domain without reflection (Orlanski, 1976. "A Simple Boundary Condition for Unbounded Hyperbolic Flows." Jrn. of Comp. Physics v. 21 (251-269)). Hope this gives you some answers.

Steven Jachec
  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
Outlet Pressure-flow coupled boundary condition (Windkessel) cfdfsi Fluent UDF and Scheme Programming 1 October 12, 2011 10:01
Boundary Condition outlet natantyt FLUENT 0 September 27, 2010 15:30
RPM in Wind Turbine Pankaj CFX 9 November 23, 2009 05:05
inlet and outlet boundary condition for turbomachinery solution siamak1424 OpenFOAM 2 August 15, 2009 11:14
Outlet boundary condition CN FLUENT 6 May 22, 2005 09:37


All times are GMT -4. The time now is 01:58.