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

Turbulence length scale

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   August 7, 2014, 16:44
Default Turbulence length scale
  #1
Senior Member
 
Join Date: Aug 2014
Posts: 160
Rep Power: 10
MissCFD is on a distinguished road
Hello,


I donít understand very well the notion of turbulence length scale. Is anybody can help me on this?



I must set the turbulence length scale for my inlet boundary condition in a circular pipe just after an elbow. I have a turbulent flow. I ask me if the turbulence length scale that I indicate for my inlet boundary condition will be the maximum length scale of eddies in the whole domain or just in the inlet of pipe ? I tend to say that it is just valid at the inlet of pipe because the thickness of the boundary layer increase and so it will generate larger structure, no ?


Also, can I say that more the turbulent velocity profil is full and more the maximum turbulence length scale is small because shear is only very important on a short height of my boundary layer relative to turbulent velocity profil less full, no ?


Thank you for your help
MissCFD is offline   Reply With Quote

Old   August 7, 2014, 18:32
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,365
Rep Power: 139
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
http://www.lmgtfy.com/?q=turbulence+length+scale

Turbulence length scale is a field variable just like velocity, pressure or temperature. This means it can take different values at different locations or times. So the inlet will have its own value of length scale determined by the flow at that location.

Length scale versus wall height: I recommend you read a turbulence modelling textbook to answer this. "Turbulence modelling for CFD" by Wilcox is a good textbook on the area.
ghorrocks is offline   Reply With Quote

Reply

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
turbulence length scale estimation stacey FLUENT 0 August 24, 2013 08:45
specify the turbulence intensity and the turbulence length bennoman75 Main CFD Forum 0 May 15, 2013 05:36
3D figures for 2D axisymmetric cases and length scale romantico Main CFD Forum 4 June 7, 2010 10:39
How to evaluate length scale for a pipe flow kb FLUENT 3 August 21, 2007 13:14
Length scale separation in LES Ray Main CFD Forum 1 June 7, 2002 08:50


All times are GMT -4. The time now is 21:55.