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

strange observations: 2

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 2, 2003, 23:42
Default strange observations: 2
  #1
kenn
Guest
 
Posts: n/a
Hi, I wrote a small 2-D code using projection finite difference on staggered mesh for a N-S problem in a periodic square--means a square with periodic BC and periodic body force. I wrote the first version three years ago in Matlab and based on classnotes which were carefully examined by the intructor, classmates and me. now,I wrote a C++ version almost independent from the previous version but based on the same trustable formulation.

as we know, when delaing with a high Re, upwinding or something like is needed unless mesh resolution is resolved.

however, I use forward time and central difference and very course mesh for any Re situations, and I didn't observe what people claim(and I also believe). instead, both version of codes always give me at least qualitative convincing results.

I am pretty puzzled, does anyone want to shed a light?
  Reply With Quote

Old   March 4, 2003, 05:25
Default here is the my explanation, could be wrongk
  #2
kenn
Guest
 
Posts: n/a
here is my explanation which could be nonsense.

in the pivotal idea under upwinding is: when the convection wins over diffusion, the downstream point should not involve to interpolate the upstream point.

if such a rule is violated, the lesser we get inaccurate solutions, the more severely we could end up with a qualitatively wrong solution.

however, the periodic is a spacial situation. the downstream is also upstream somewhere.
  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
Strange Flamelet Generation Problem tar FLUENT 11 March 22, 2014 12:52
Strange Nut behaviour with K-OmegaSST nicolarre OpenFOAM 8 April 3, 2013 09:48
A Strange Problem in making Parallel (Ansys/CFX 12) a.sarami CFX 13 October 7, 2010 02:33
Strange Problem With updating the library farhagim OpenFOAM 0 August 10, 2010 13:34
strange observations: 1 kenn Main CFD Forum 0 March 2, 2003 23:33


All times are GMT -4. The time now is 22:45.