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

Defining time step size

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

Reply
 
LinkBack Thread Tools Display Modes
Old   November 27, 2003, 10:11
Default Defining time step size
  #1
kilcoo316
Guest
 
Posts: n/a
OK, this is a simple problem, that I haven't got my head round,

I have a test case to model, which has a characteristic height 0.066m (as used for E in K-E). For running the URANS sims for vortex shedding, in kelvin-helmhotz (K-H) form. I have taken the size of the first K-H instability, and calculated the time the free-stream velocity takes to pass over it, gave it 30 steps over the motion, which results in a timestep of 0.000006 sec. Is that too small?

The Cd and Cl traces are extremely unsteady, varying between 10 and 0 for Cl( high as 30 - -15 near start) and 5 and 0 for Cd (30 - -5 near start).

Length of 1st K-H approx = 0.005423m (0.000180 sec/periodic motion) Length of test case = 0.371m vel = 30m/s (Re approx 9*10^5)

Thanks for any advice.
  Reply With Quote

Old   December 1, 2003, 12:07
Default Re: Defining time step size
  #2
kilcoo316
Guest
 
Posts: n/a
is this the right way to go about it? anyone?
  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
How to write k and epsilon before the abnormal end xiuying OpenFOAM Running, Solving & CFD 8 August 27, 2013 15:33
Time step size, number of time steps and max iterations per time step guido_88 FLUENT 4 August 30, 2012 14:49
Orifice Plate with a fully developed flow - Problems with convergence jonmec OpenFOAM Running, Solving & CFD 3 July 28, 2011 05:24
Problems in compiling paraview in Suse 10.3 platform chiven OpenFOAM Installation 3 December 1, 2009 08:21
Transient simulation not converging skabilan OpenFOAM Running, Solving & CFD 12 September 17, 2007 17:48


All times are GMT -4. The time now is 04:33.