# Outlet boundary condition

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 May 12, 2005, 09:38 Outlet boundary condition #1 CN Guest   Posts: n/a Sponsored Links Dear Fluent Users, I've a question regarding the outlet boundary condition. Fluent Manual states that the Outlet BC is "appropriate where the exit flow is close to a fully developed condition". If my inlet B.C. (e.g. inlet velocity) changes with time, i.e. unsteady, the outlet condition cannot be fully developed. Is there any BC at outlet which I can use? Thanks a lot.

 May 12, 2005, 14:14 Re: Outlet boundary condition #2 tucker Guest   Posts: n/a Why don't you use a pressure outlet BC?

 May 12, 2005, 16:41 Re: Outlet boundary condition #3 CN Guest   Posts: n/a hi, the conditions at the outlet (i.e. velocity and pressure) are dependent on the flow conditions in the interior, and this is best described by the outlet boundary condition, except that Fluent requires the flow at outlet to be fully developed. If I were to pre-determine the outlet condition using the pressure outlet BC, the simulation would not be modelling the actual experimental conditions. Any advice on how to go about doing this? Perhaps, would this problem be solved by other CFD software? I'm quite new to CFD. THANKS!!

 May 12, 2005, 17:05 Re: Outlet boundary condition #4 Jason Guest   Posts: n/a What is it you are modeling? One of the possibilities would be to extend your computational domain... for example if you were modeling a tube the exits into a room, then you could create a large volume at the exit of your area of interest and then apply the constant (ambient) pressure to this area. At some point your experiment has to "dump" to a constant pressure, so figure out where that is and model it. Either that, or the flow loops back around (like a continuous flow wind tunnel). Either way, it seems like you're going to have to extend your domain and take the hit on the size of the mesh in order to properly model what it is you've got. Hope this helps, and good luck, Jason

 May 18, 2005, 00:51 Re: Outlet boundary condition #5 venugopal Guest   Posts: n/a You can use outflow boundary condition also. The important thing you have to follow is you have to extend your domain. so the the flow will not disturb the outlet conditions. Try to extend your computational domain at the exit. Hope it will work. VenuGopal. S

 May 22, 2005, 02:03 Re: Outlet boundary condition #6 pratap behera Guest   Posts: n/a how to extend the computational domain.... pl help i am quite new with cfd

 May 22, 2005, 09:37 Re: Outlet boundary condition #7 venugopal Guest   Posts: n/a can you explain me about your geometry.

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post cfdfsi Fluent UDF and Scheme Programming 3 July 21, 2017 12:30 natantyt FLUENT 0 September 27, 2010 15:30 Pankaj CFX 9 November 23, 2009 05:05 siamak1424 OpenFOAM 2 August 15, 2009 11:14 YY CFX 7 April 20, 2008 22:04