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

time step size

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

Reply
 
LinkBack Thread Tools Display Modes
Old   July 31, 2005, 06:39
Default time step size
  #1
Sham
Guest
 
Posts: n/a
Hi all,

Does anyone know how to calculate a time step size? I am modelling a cylinder in water. I use a time step size of 0.005 and the solution takes more than 48 hours to iterate. Is this normal?

Thanks.

Sham.
  Reply With Quote

Old   July 31, 2005, 07:12
Default Re: time step size
  #2
Swarup
Guest
 
Posts: n/a
Calculate characteristic time scales of processes (momentum, mass and heat transfer and reaction rate)involved in your problem. you should use a time step smaller that the smallest characteristic time you have. this method properly resolves the fatsest and slowest of the processes. however, if you are only interested in obtaining a steady state solution and are not bothered about temporal accuracy of solution, then you should take advantage of unconditional stability of implicit method and use larger time step. also, if you are not encountering high velocities, then using segregated solver will definitely improve speed of computation. another thing you may look at is whether your mesh is very fine. Hope some of these things will help in reducing time of computation.

Best of Luck,

Swarup.
  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
critical error during installation of openfoam Fabio88 OpenFOAM Installation 21 June 2, 2010 03:01
Modeling in micron scale using icoFoam m9819348 OpenFOAM Running, Solving & CFD 7 October 27, 2007 00:36
Transient simulation not converging skabilan OpenFOAM Running, Solving & CFD 12 September 17, 2007 17:48
natural convection - time step size co2 FLUENT 7 June 3, 2004 21:56
how to increase time step size? co2 FLUENT 6 May 17, 2004 07:25


All times are GMT -4. The time now is 01:36.