CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

pressure outlet BC for Boussinesq with Fluent

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

LinkBack Thread Tools Display Modes
Old   October 19, 2007, 09:38
Default pressure outlet BC for Boussinesq with Fluent
Posts: n/a

I'm trying to solve a time dependent problem with Fluent using the boussinesq approximation. I have a velocity inlet and a pressure outlet (outflow is not good if the density is not constant). if I keep a constant gauge pressure at the outlet, after a certain time a gradient of pressure appears at the outlet creating a high velocity and there is divergence. I ve written an udf with a linear profile of pressure as well and used it at the outlet BC but it doesnt work either. So i'm wondering about the settings at the outlet.

thanks in advance, stéphane
  Reply With Quote

Old   October 20, 2007, 07:09
Default Re: pressure outlet BC for Boussinesq with Fluent
Posts: n/a
Have you tried using no outlet b/c?

It may be better to set a pressure condition in your entering flow, as an initial condition.

I have found that setting the incorrect exit b/c in many simulations - especially pipe & duct flows - is seen by the flow field as a constraint. The unconstrained 'free exit' (do-nothing b/c) leaves the flow to decided what it wants to do.

Be careful of placing restraints where they may not be required. This can be one of the reasons for solver divergence via a so-called 'pressure blow-up'.

An exiting fluid will react differently in terms of pressure wave return sign, depending on the b/c used.


<> <> <>

  Reply With Quote


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
UDF for pressure at outlet mireis FLUENT 0 August 12, 2010 06:19
Pressure Outlet setting CoG STAR-CCM+ 4 June 9, 2010 21:47
Pressure Rise Error emueller CFX 0 May 5, 2009 11:08
pressure outlet BC for incompressible flow khaiching Main CFD Forum 6 October 15, 2005 02:58
Fluent 5.2, UDF and Pressure BC's Alfonso Ferrandez FLUENT 0 May 4, 2000 07:02

All times are GMT -4. The time now is 10:18.