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

Temporal accuracy

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 29, 2008, 06:32
Default Temporal accuracy
  #1
ganesh
Guest
 
Posts: n/a
Dear Friends,

I am trying to establish the order of accuracy of the time discretisation procedure for my unsteady code. I use a BDF3 scheme so my design accuracy has to be 3. The test problem is the Sod shock tube problem in 2D and care is taken that the left and right boundaries do not come into play (in terms of reflections). I am having problems getting the design accuracy even on static grids. Specifically, I have the following questions.

1. BDF3 is not self--starting and therefore I used CN (Crank--Nicholson) for the first two iterations and start off BDF3. CN is second order accurate, what effect does this have on the temporal accuracy studies ? I have already tested CN2 for second order accuracy both on static/moving grids.

2. What is the best way to start-up BDF3 ?

3. Instead of any special start--up if the initial values are themselves used until values at the time level become available, will there be a detrimental effect on time accuracy ?

It is known that a single step with a large local error could be dominant over all the other steps taken to reach upto final time in an unsteady simulation, and I would like to know the opinion of those who have had experiences with BDF for unsteady flows.

Regards and thanks in advance,

Ganesh

  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
Grid refinement study for Order of accuracy and GCI Chander CFX 5 May 3, 2011 20:13
Accuracy and convergence pawan1989 FLUENT 5 April 15, 2010 18:17
effect of order of temporal accuracy zonexo Main CFD Forum 4 August 14, 2006 01:36
accuracy of Discontinuous Galerkin Qu Kun Main CFD Forum 0 September 6, 2004 10:19
time accuracy test nat Main CFD Forum 0 April 2, 2003 00:24


All times are GMT -4. The time now is 00:48.