CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Main CFD Forum

2d NS supersonic BC

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 2, 1999, 13:36
Default 2d NS supersonic BC
  #1
thampy
Guest
 
Posts: n/a
hi,

Could anyone tell me as to what are the flow parameters that i need to specify as my exit BC when i'm simulating 2d NS supersonic flow ?

thanking you thampy
  Reply With Quote

Old   September 2, 1999, 13:58
Default Re: 2d NS supersonic BC
  #2
John C. Chien
Guest
 
Posts: n/a
(1). In supersonic flow, the local solution depends on the upstream condition or solution. It is controlled by the characteristics network. (2). So, you can give it a rough number at eixt B.C., it is not going to affect the interior points solution at all, as long as the flow is supersonic.
  Reply With Quote

Old   September 2, 1999, 14:26
Default Re: 2d NS supersonic BC
  #3
stephane baralon
Guest
 
Posts: n/a
If your flow is axially supersonic, then all characteristics goes out of the domain: you don't need to specify anything.

If your flow has a Y velocity component and also is not axially supersonic(M>1 but Mx<1) then you need to specify one information (one characteristic propagates inside the domain). Usually the pressure.

If your flow has a Y velocity component and also is axially supersonic, then again you don't need to specify anything.

  Reply With Quote

Old   September 2, 1999, 14:56
Default Re: 2d NS supersonic BC
  #4
Hongjun Li
Guest
 
Posts: n/a
Good point! To make it more general, you may say that if the Mach number component in the direction normal to the boundary surface is great than 1 (Mn > 1), then the exit BCs are not needed. The boundary values can be extrapolated from the upstream grid point. If Mn<1, although Mtotal is greater than 1, the exit boundary is still treated as subsonic. In that case, (if 2-D) three variables should be extrapolated from the upstream, and one variable must be specified at the exit.
  Reply With Quote

Old   September 3, 1999, 11:44
Default Re: 2d NS supersonic BC
  #5
clifford bradford
Guest
 
Posts: n/a
the above are correct but you have to be careful if you have a boundary layer or wake exiting your domain the flow in that region will/may be subsonicin which case you'll need one exit BC. in which case the pressure is usually appropriate
  Reply With Quote

Reply

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
Probelm with supersonic exhaust to ambient newj CFX 2 August 9, 2012 18:01
Flow in Supersonic MHD Channel Antanas CFX 6 February 13, 2012 15:49
CFX problems with supersonic inlet condition - Inlet values in CFX-Post are wrong jannnesss CFX 5 February 25, 2011 17:24
Supersonic flow abishek FLUENT 3 July 28, 2008 06:07
CFD code for supersonic flows hedy Main CFD Forum 9 April 16, 2007 10:56


All times are GMT -4. The time now is 05:38.