CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

Timescale convergence?!

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 15, 2016, 07:45
Default Timescale convergence?!
  #1
New Member
 
Tim
Join Date: May 2014
Posts: 8
Rep Power: 12
Schwimmy is on a distinguished road
Hi guys,

I'm running a NACA0015 profile at low reynolds numbers (10000-1000000) with steady sst including gamma-theta transition model. I varied my timescale to become a converged (steady state) solution. But I found out, that in some cases both decreasing and increasing the timescale from my converged timestep gives me an oscillating (transient) result.

My question is, does the "good" timescale maybe damp transient effects so the solution can convergate?

Cheers
Schwimmy is offline   Reply With Quote

Old   April 15, 2016, 13:57
Default
  #2
Senior Member
 
Join Date: Jun 2009
Posts: 174
Rep Power: 16
turbo is on a distinguished road
at what AOA?
turbo is offline   Reply With Quote

Old   April 16, 2016, 04:44
Default
  #3
New Member
 
Tim
Join Date: May 2014
Posts: 8
Rep Power: 12
Schwimmy is on a distinguished road
AoA=0, critical Re from 10000 til 100000. above 100000 it's ok.
Schwimmy is offline   Reply With Quote

Old   April 16, 2016, 06:42
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,727
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
If the flow is not in the gross separated flow regime (which I suppose it is not at AOA=0), then this is probably a laminar separation bubble. They tend to be unstable and jiggle about quite a bit. If the bubble is small it probably does not affect things much but at low-moderate Re (50k-200k for many airfoils) the separation bubble can be large. It might be important in this Re range.
ghorrocks is offline   Reply With Quote

Reply

Tags
steady, timescale, transient

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Convergence Centurion2011 FLUENT 48 June 14, 2022 23:29
Timescale and convergence of steady state simu with CFX Mason liu CFX 7 December 25, 2015 22:12
Is this convergence real? Chander CFX 8 October 21, 2011 19:59
Force can not converge colopolo CFX 13 October 4, 2011 22:03
Convergence of CFX field in FSI analysis nasdak CFX 2 June 29, 2009 01:17


All times are GMT -4. The time now is 18:23.