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

Turbulent length scale

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

Reply
 
LinkBack Thread Tools Display Modes
Old   February 22, 2017, 19:33
Default Turbulent length scale
  #1
Senior Member
 
Join Date: Aug 2014
Posts: 129
Rep Power: 5
MissCFD is on a distinguished road
Can somebody confirm me that the turbulent length scale that we need to input as a inlet condition (with the turbulent intensity) corresponds well to integral scale l which is the size of the largest eddies and which is also to be found in this formula:

\eta/l=Re^{-3/4} where \eta is the Kolmogorov scale.

The reason I ask is that there is a lot of notation for turbulent length scale: l, l_t, L, L_t, etc.

Thank you for your help !
MissCFD is offline   Reply With Quote

Old   February 23, 2017, 02:12
Default
  #2
Senior Member
 
piu58's Avatar
 
Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
Posts: 271
Rep Power: 4
piu58 is on a distinguished road
l is the length of the large eddies. It should not be larger than L (the size of the problem) of course. l can be guessed.

For pipe flows:

l=0.038 d

d is the hydraulic diameter, which is identical the diameter for round pipes. For rectangular ones:

d = 2 \frac{ab}{a+b}

For flow around / past bodies:

l = 0.07 L

L is the size of the problem, for cylinders and spheres the diameter, for other bodies the diameter of the flow directed area.
__________________
Uwe Pilz
--
Sie ahnen nicht, wieviel Poesie in der Berechnung
einer Logarithmentafel enthalten ist (Carl Friedrich Gauß)
piu58 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
Calculation for Turbulent Length Scale aqib CFX 4 December 14, 2010 06:24
Turbulent Length Scale aqib FLUENT 0 December 11, 2010 02:53
turbulent length scale Cathy FLUENT 1 July 9, 2003 07:13
Von Karman Integral Length Scale Txingurri Main CFD Forum 0 May 2, 2002 12:05
Length scale was zero chris Siemens 2 September 10, 2001 09:12


All times are GMT -4. The time now is 03:41.