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

negative densities

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

Reply
 
LinkBack Thread Tools Display Modes
Old   January 11, 2002, 11:53
Default negative densities
  #1
Sabatini
Guest
 
Posts: n/a
hay People

how i can ileminate the negative densities in my model thanks
  Reply With Quote

Old   January 11, 2002, 17:11
Default Re: negative densities
  #2
James
Guest
 
Posts: n/a
1. lower under-relaxation factor for pressure and/or velocity

2. enhance the number of sweeps

3. Have a look at the answers posted here in former times

  Reply With Quote

Old   January 14, 2002, 23:42
Default Re: negative densities
  #3
ckuo
Guest
 
Posts: n/a
If this came with unreasonable high velocity and at very beginning of iteration, you may never get rid of it with your target flow rate. Maybe, one way to get around it (I assume your mesh is OK) is to reduce your start-up flow rate to lower initial velocity. Once flow pattern developped to reasonable and stable, ram up flow rate to approach targe B.C.
  Reply With Quote

Old   January 15, 2002, 21:43
Default Re: negative densities
  #4
star-user
Guest
 
Posts: n/a
Perhaps just keeping the density constant for a few 100 iterations may help.
  Reply With Quote

Old   January 31, 2002, 09:06
Default Re: negative densities
  #5
stephen
Guest
 
Posts: n/a
Make sure you are using a bounded differencing scheme such as UD or MARS. In fact don't ever use a differencing scheme that isn't UD or MARS (and only use UD as a last resort)

Stephen
  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
negative densities john CD-adapco 0 March 19, 2008 07:32
negative densities Riyaz Ahamed CD-adapco 2 August 14, 2007 01:47
Negative Densities Chris CD-adapco 4 June 25, 2007 08:39
negative densities CMB CD-adapco 4 January 4, 2004 03:41
negative densities. Mihir CD-adapco 4 December 9, 2002 22:04


All times are GMT -4. The time now is 15:24.