CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

Switching between open and closed boundary conditions in a transient solution

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 10, 2013, 16:33
Default Switching between open and closed boundary conditions in a transient solution
  #1
New Member
 
Joseph Tipton
Join Date: Jun 2010
Posts: 27
Rep Power: 15
jtipton2 is on a distinguished road
Hello all,

I am looking at modeling an air intake for an automotive application. From what I've come to understand, it is important to use acoustic resonance to enhance the pressure of the flow when the inlet opens.

I would like to use CFX to model this as a transient problem. The domain would be the manifold and intake header up to the inlet valve.

Would it be possible to oscillate between a wall and pressure outlet conditions at the inlet depending on time? How could I achieve this? I've seen some posts by Glenn H. about doing this at an interface, but this is a domain boundary.

Any guidance would be much appreciated.

Best Regards,

Joseph Tipton
jtipton2 is offline   Reply With Quote

Old   October 10, 2013, 18:31
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,631
Rep Power: 142
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
A better way of modelling the inlet valve is to define it as a mass flow condition and give it the mass flow versus time curve. You generally know the mass flow better than the pressure anyway, as you have to get the total mass flow correct (to get the correct volumetric efficiency) and that is difficult with a pressure boundary. When the valve is shut this mass flow is obviously zero. There is no need to define a wall when the flow is zero, just defining zero mass flow is good enough.

This approach works fine and I have used it many times to model inlet and exhaust manifolds. You cannot model the coupling of the volumetric efficiency with the inlet manifold wave with this approach, that is quite a bit harder to model as you need a full engine model.
ghorrocks is offline   Reply With Quote

Reply

Tags
transient bc

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Boundary conditions for water jet into air in a closed chamber vishal_s OpenFOAM Running, Solving & CFD 0 August 20, 2013 04:27
Help UDF to Boundary Conditions in Closed Loop Pipe Blader Fluent UDF and Scheme Programming 2 May 14, 2012 10:48
Problems with boundary conditions - velocity and pressure not zero M_Flodin FLUENT 0 April 1, 2011 10:32
Change boundary conditions during transient simulation ZenCef FLUENT 0 February 6, 2011 17:10
Boundary conditions in CFX-Pre Saikat CFX 2 February 10, 2005 08:22


All times are GMT -4. The time now is 14:16.