CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

time averaged unsteady versus steady solution

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

LinkBack Thread Tools Display Modes
Old   June 27, 2008, 02:55
Default time averaged unsteady versus steady solution
CFD - NewBe
Posts: n/a
Which time averaging technics are used for unsteady solutions and where are the differences to a steady calculation?

If somebody can give a comprehensive answer, that would be great.

Thankful, CFD-NewBe
  Reply With Quote

Old   June 27, 2008, 04:17
Default Re: time averaged unsteady versus steady solution
Posts: n/a
RANS models are for the time averaging steady solution. For unsteady solution the equation will be changed to Unsteady-RANS (URANS) by participating the time derivative. The techniques of RANS and URANS can be different, related to the simulation approach. It is possible to contribute the time derivative for RANS and reach the steady solution by time marching. But in this case the simulation becomes slower. It is the case many programmers ignore the time derivative and solve it iteratively. If you consider the time derivative, the phenomena, and also the geometry will determine your final solution, either steady or unsteady. If the final solution is steady, you will have a RANS solution. But it is not always possible to have an steady solution. For example the vortex shedding behind a cylinder is always unsteady, and the solution must be done by considering the time term.
  Reply With Quote


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
calculation diverge after continue to run zhajingjing OpenFOAM 0 April 28, 2010 04:35
Transient simulation not converging skabilan OpenFOAM Running, Solving & CFD 12 September 17, 2007 17:48
13 versus 14 steady unsteady and moving meshes lr103476 OpenFOAM Running, Solving & CFD 15 July 16, 2007 10:47
AMG versus ICCG msrinath80 OpenFOAM Running, Solving & CFD 2 November 7, 2006 16:15
unsteady calcs in FLUENT Sanjay Padhiar Main CFD Forum 1 March 31, 1999 12:32

All times are GMT -4. The time now is 14:20.