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

Second order time accuracy

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 29, 2006, 01:11
Default Second order time accuracy
  #1
Aditya
Guest
 
Posts: n/a
A second order Space discretization reduces the damping and give a high amplitude and high frequency solution.

What should I expect from Second order time discretization such as crank nicolson method over the first order discretization solution

Thanks aditya
  Reply With Quote

Old   September 29, 2006, 11:25
Default Re: Second order time accuracy
  #2
agg
Guest
 
Posts: n/a
You should expect an improvement in your solution, unless you are solving a steady problem in which case I'm not sure if there is a big improvement
  Reply With Quote

Old   September 30, 2006, 00:34
Default Re: Second order time accuracy
  #3
ganesh
Guest
 
Posts: n/a
Dear Aditya,

Second order temporal discretisation does not offer much for steady state problems, because you are driving your temporal terms to zero. However, for time -dependent flows where your require time accurate computations, the temoral order of accuracy becomes equally important as the spatial order of accuracy. The easy way to view the advantage is to have an analogy with the higher order spatial discretisation procedure. Second order time discretisation procedure do to the temporal scale what second order spatial discretisation procedures do to the spatial scale. The choice of the temporal scheme also depends on its stability. Thus, for a typical unsteady problem involving pitching airfoils or moving shocks, second order temporal discretisation such as the Crank Nicholson or the Three point Backward difference is employed. If you want to visually get an idea of how time accurate computations are important, you can see for yourself that in case of a pitching airfoil, a first order time accurate scheme would not predict the hysterisis loop correctly, while a second order accurate scheme does, and for aeroelastic problems where flutter predictions are of concern, first order temporal accuracy would result in erroneous predictions.

Hope this helps

Regards,

Ganesh

  Reply With Quote

Old   October 2, 2006, 13:16
Default Re: Second order time accuracy
  #4
HelpfulSoul
Guest
 
Posts: n/a
If you want to visually get an idea of how time accurate computations are important, you can see for yourself that in case of a pitching airfoil, a first order time accurate scheme would not predict the hysterisis loop correctly, while a second order accurate scheme does, and for aeroelastic problems where flutter predictions are of concern, first order temporal accuracy would result in erroneous predictions

Not strictly true. Provided the time step is small enough the first order scheme will be just as good but more expensive (provided the solution is time step converged). But generally speaking, for a given time step (rather than a time-step converged solution) we would expect better accuracy.

  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
Order of accuracy: 1st or 2nd order? fisch OpenFOAM Running, Solving & CFD 2 July 6, 2011 04:37
calculation diverge after continue to run zhajingjing OpenFOAM 0 April 28, 2010 04:35
PostChannel maka OpenFOAM Post-Processing 5 July 22, 2009 09:15
Modeling in micron scale using icoFoam m9819348 OpenFOAM Running, Solving & CFD 7 October 27, 2007 00:36
CFL number and time accuracy for LES Li Yang Main CFD Forum 2 August 1, 2002 06:11


All times are GMT -4. The time now is 02:04.