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

How to model the NR eqns in a domain with empty space

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 13, 2009, 12:14
Default How to model the NR eqns in a domain with empty space
  #1
New Member
 
Join Date: Apr 2009
Posts: 17
Rep Power: 16
Vasilis is on a distinguished road
I am trying to solve the NR eqns in a domain which surrounds an empty space. To make my work a little easier I have created a mesh for the entire domain. So, I have velocity and pressure unknowns in the empty space. Now, I am not sure about the boundary conditions that I should use on the boundaries of the empty space. Certainly, the velocity will be zero, but what about the pressure.

I am solving the NR eqns with the FEM, and the fluid is incompressible.

For the moment, I am only setting the velocity to zero at these boundaries, but I believe that the solution is not very accurate. I believe that the correct way to solve this problem is to modify the code so that the continuity equation on the void boundaries does not have any contribution from the void. In this way, I am having two domains, and there is no interaction between the void and the domain of interest.
Unfortunately, if I do this, the Newton-Raphson scheme does not converge.

Does anybody have an idea about how to model this problem. I would like to say here that I am not interested in a solution which does not consider the empty space, i.e., I do not want to construct a mesh which goes around the empty space.

I thank you in advance for your time.
Vasilis is offline   Reply With Quote

Old   April 14, 2009, 05:35
Default
  #2
New Member
 
Join Date: Apr 2009
Posts: 17
Rep Power: 16
Vasilis is on a distinguished road
Newton Raphson would diverge because I had forgotten to update the residuals.
Now, it converges within a couple of iterations.
Vasilis is offline   Reply With Quote

Reply

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
CFX domain error message about multiphase model Jane CFX 0 March 5, 2009 11:30
Reynolds transport, turbulence model, etc Beginner Main CFD Forum 1 January 7, 2009 06:36
LES and combustion model Margherita Cadorin CFX 0 October 29, 2008 06:24
How can I increase Heat Transfer at Domain Interf? B.Simon CFX 3 October 28, 2008 19:53
Concentric tube heat exchanger (Air-Water) Young CFX 5 October 7, 2008 00:17


All times are GMT -4. The time now is 05:52.