# CFX Boundary condition

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

 August 20, 2013, 02:29 CFX Boundary condition #1 New Member   Rameez Join Date: May 2013 Posts: 19 Rep Power: 6 Hello buddies, I am trying to simulate a flow over an axial turbine whose rpm is low around 500 rpm. I know only the pressure drop across the turbine and volumetric flow rate. Fluid medium is ideal gas air. Using vol. flow rate,i could identify my inlet boundary condition as normal speed or mass flow inlet, but I'm very confused with the outlet boundary condition. Please help.

 August 20, 2013, 06:24 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,310 Rep Power: 110 Then your outlet will be some form of pressure boundary. Read the CFX documentation on recommendations on boundary conditions for tips on exactly what sort pf pressure boundary, and the best practises guide for turbomachinery (also in the CFX documentation).

 August 20, 2013, 06:54 #3 New Member   Rameez Join Date: May 2013 Posts: 19 Rep Power: 6 Yeah i have practised the tutorials, here what i wanted to ask is, Can i specify pressure outlet as 0 Pa, keeping reference pressure as 0 Pa too Or i should calculate the inlet pressure and then as i know pressure drop, subtract it from inlet pressure to specify the pressure outlet ? Or should i simply keep the outlet open to atmosphere

 August 20, 2013, 07:09 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,310 Rep Power: 110 I was not referring to the tutorials. I was referring to the CFX documentation which contains a lot of information about how to use the software effectively. No, your outlet pressure is not going to be absolute zero pressure. If it is atmospheric pressure (1 bar absolute) then use 1 bar reference pressure and 0 bar pressure on the outlet.

 September 4, 2013, 01:02 Vice Versa #5 New Member   Rameez Join Date: May 2013 Posts: 19 Rep Power: 6 Can we do vice versa? 0 bar as reference pressure and outlet as 1 bar because if i specify 1 bar as reference, it may effect my inlet condition. Thanks

 September 4, 2013, 02:57 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,310 Rep Power: 110 You do not seem to understand. If your inlet is 2 bar absolute and the outlet is 1 bar absolute then use a reference pressure of 1 bar, an inlet of 1 bar and an outlet of 0 bar. All pressures are relative to the reference pressure. So if you change the reference pressure you change all pressures in the simulation.

 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 volo87 CFX 5 June 14, 2013 17:44 murali CFX 5 August 3, 2012 08:56 jannnesss CFX 5 February 25, 2011 17:24 CFD XUE FLUENT 0 July 9, 2010 02:53 Pankaj CFX 9 November 23, 2009 05:05

All times are GMT -4. The time now is 22:35.