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

Steady vs Unsteady

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 8, 2010, 10:39
Default Steady vs Unsteady
  #1
New Member
 
Join Date: Jan 2010
Posts: 4
Rep Power: 7
Steff54 is on a distinguished road
Hello,

I have a question, maybe stupid, but I really need answers.
I am running a simulation in 3D, with constant boundary conditions and I am particularly interested in the flow (recirculation, eddy, etc.). Since all the variables are constants, does it make any sense to run an unsteady simulation?

SteffB
Steff54 is offline   Reply With Quote

Old   April 8, 2010, 15:13
Default
  #2
New Member
 
Fidel Arzola
Join Date: Mar 2010
Location: Venezuela
Posts: 5
Rep Power: 7
farzola is on a distinguished road
Quote:
Originally Posted by Steff54 View Post
Hello,

I have a question, maybe stupid, but I really need answers.
I am running a simulation in 3D, with constant boundary conditions and I am particularly interested in the flow (recirculation, eddy, etc.). Since all the variables are constants, does it make any sense to run an unsteady simulation?

SteffB

Hello,
In my opinion yes!, for instance, I simulated the hydrodynamic of a cavitating vortex in the draft tube of a Francis turbine, called Vortex Rope in the field of hydroturbines, just imposing a constant and symmetric velocity profile (taked from 2D LDV measurements) in the inlet and then pressure fluctuactions were very well computed and I never used a rotor-stator simulation. But I was sure that that phenomenon is time-dependant and transient simulations were necesary. Transient phenomena are also dependent of geometry, boundary conditions, numrical scheme, time and spatial resolution, etc...

A final suggestion, used a converged steady simulation to start a transient one with a well-defined time step and give enought time to capture expected physical time-dependant phenomena.
__________________
Thanks,
Fidel
farzola is offline   Reply With Quote

Old   April 9, 2010, 05:59
Default think "NATURE"
  #3
New Member
 
Amin Feizi
Join Date: Apr 2010
Posts: 8
Rep Power: 7
AminFeizi is on a distinguished road
Hi,

There is no inconvenience in running an unsteady simulation whith steady BCs .
But it is better to think "NATURE", sort of speaking.
There is no instant changes in boundaries in the reality.
So the best results are obtained with unsteady BCs if you know them.

Good Luck,
Amin
AminFeizi is offline   Reply With Quote

Old   April 9, 2010, 10:12
Default
  #4
New Member
 
Join Date: Jan 2010
Posts: 4
Rep Power: 7
Steff54 is on a distinguished road
Hi,

Thanks for your answer guys, it was very useful.
Steff54 is offline   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
Steady and unsteady solves kospan FLUENT 3 October 28, 2008 09:15
Steady needs unsteady. nico Main CFD Forum 0 September 21, 2007 04:50
shifting from Unsteady to steady Abhinav FLUENT 0 July 29, 2007 22:53
Turbulent: Steady or Unsteady: confusion prem FLUENT 0 March 30, 2006 10:40
steady or unsteady? (in dpm) winnie FLUENT 1 April 28, 2003 11:30


All times are GMT -4. The time now is 08:40.