# Which type of boundary conditions ?

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

 September 22, 2011, 16:11 Which type of boundary conditions ? #1 New Member   Corrado Join Date: Mar 2009 Posts: 11 Rep Power: 8 Hi all, I'm analyzing a wind tunnel like duct; air is moved by a fan placed a the exit with a given mass flow rate. At inlet I have environment pressure and zero velocity. I wonder which are the correct boundary conditions for such case. Help is appreciated. Thank you

 September 23, 2011, 03:11 #2 Senior Member   Mohammad Join Date: Feb 2010 Location: Shiraz, Iran Posts: 108 Rep Power: 7 hi, if you have a duct, you cant have zero velocity at the inlet. zero velocity is for infinitely upstream condition. I dont know what is you problem and domain but if you know the pressure drop between inlet and outlet of duct(just before the fan) you can use pressure inlet and outlet. but if not, if you know mass flow rate, use mass flow inlet and pressure outlet. also if the problem is incompressible and the inlet is far enough from the body in the tunnel, you can use velocity inlet at inlet with V=Q/A and a boundary layer would appear and grows at the beginning of the duct. yours, mohammad

 September 23, 2011, 05:04 #3 New Member   Corrado Join Date: Mar 2009 Posts: 11 Rep Power: 8 mohammad, thank you for your reply. The domain is very simple: a tube and ,as I said, you can think about it like a windtunnel. Since the flow is driven by a fan placed at the end (outlet) of the tube, I suppose that at the inlet I have the following condition: -flow is at rest at inlet - pressure at inlet equals pressure of environement. I know the mass flow rate at the fan and on the basis of conditions above I need to evaluate the flow speed at some section along the tube. But I'm a little confused about which boundary condition , available in Fluent, I can use. Mass flow rate is available at inlet and not at outlet as I would like..

 September 23, 2011, 06:37 #4 Senior Member   Mohammad Join Date: Feb 2010 Location: Shiraz, Iran Posts: 108 Rep Power: 7 hi, by continuity it is obvious that mass flow rate at outlet is exactly equal to mass flow rate at inlet. so at inlet there is no rested air. as I previously said rest is for infinitly upstream, not for inlet. simply use "mass flow inlet" for inlet and "pressure outlet" for outlet yours, mohammad

 September 23, 2011, 07:50 #5 New Member   Corrado Join Date: Mar 2009 Posts: 11 Rep Power: 8 I will proceed on the basis of your suggestion. Your help is appreciated very much. Corrado

 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 Attesz CFX 7 January 5, 2013 04:32 Wolle OpenFOAM 2 April 11, 2011 07:32 mehrdadeng CFX 10 February 25, 2011 06:25 daniel_mills OpenFOAM Running, Solving & CFD 44 February 17, 2011 18:08 Pankaj CFX 9 November 23, 2009 05:05

All times are GMT -4. The time now is 21:33.

 Contact Us - CFD Online - Top