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

incompressible NS equation

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 22, 1999, 09:04
Default incompressible NS equation
  #1
laliong
Guest
 
Posts: n/a
Hello,

I'm trying to solve incompressible NS equations. However, the pressure equation is a laplacian equation with Neumann boundary condition. Does anybody know how to solve this equation since the matrix of the system of linear equations is a singular matrix ?

Thanks a lot.

  Reply With Quote

Old   April 22, 1999, 12:15
Default Re: incompressible NS equation
  #2
Jim Park
Guest
 
Posts: n/a
If I remember this correctly, the singularity indicates that the pressure can be determined to within a constant value. In other words, your solution will be adequate to correct the velocity field to insure continuity but you won't actually know the pressure level.

The folks at the Los Alamos Nat'l Lab who invented this approach (MAC, SMAC, ICE, ...) solved the LaPlace eqn iteratively, by over-relaxation. As an alternative, I think you can specify the pressure at one point, making the matrix non-singular so it can be solved by elimination, etc. But your solution is still only known to within a constant (the value you specified).

Good Luck!
  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
Calculation of the Governing Equations Mihail CFX 7 September 7, 2014 06:27
Constant velocity of the material Sas CFX 15 July 13, 2010 08:56
Viscosity and the Energy Equation Rich Main CFD Forum 0 December 16, 2009 15:01
mass flow in is not equal to mass flow out saii CFX 2 September 18, 2009 08:07
continuity equation Rafal Main CFD Forum 4 November 29, 2006 10:27


All times are GMT -4. The time now is 15:18.