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

what is fully developed turbulence?

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 23, 2006, 16:24
Default what is fully developed turbulence?
  #1
sarah_ron
Guest
 
Posts: n/a
Dear all,

I am now confusing about the fundamental concepts of turbulence.

What's fully developed turbulence? Surely we could see the Re is high enough, but we don't know the exact value for the word "high" for a given complex flow. There should exist some criteria to determine the flow state. I have found some one use turbulent energy spectrum to judge whether it is fully developed turbulence or not based on -5/3. I don't know whether this is a general method.

Any comment is welcome, if possible please give the references. thanks a lot!

regards, sincerely, sarah
  Reply With Quote

Old   October 23, 2006, 17:13
Default Re: what is fully developed turbulence?
  #2
Mani
Guest
 
Posts: n/a
Fully developed turbulence seems synonymous to "fully turbulent" as opposed to transitional or intermittent turbulent/laminar. The question is not, if the turbulence level is high or low, it's whether the flow at a given location is turbulent at all times or intermittent. Fully turbulent flow will typically show the -5/3 power in the energy spectrum, if there is a wide enough cascade of scales. I don't have a definite reference, but try any book on turbulence, e.g. "Turbulent Flows" by S. Pope.
  Reply With Quote

Old   October 24, 2006, 08:10
Default Re: what is fully developed turbulence?
  #3
mar
Guest
 
Posts: n/a
in order to clear the question you can think at a flow on flat plate.

In the nearby of the leading edge the flow is laminar because the Rex (the Reynolds number based on the abscissa) is small. Proceding forward the REx increases and the flow become transitional when the Rex is approximately 500.000.

Going further the flow becomes more and more turbulent.

When the statistics of the turbulence don't vary at all and reach a defined decaying (energy transfer between eddies) the flow is fully turbulent.

The same things happen in time for a given location when there is a variable boundary condition.

  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
Fully developed flow in Star-cd SMM STAR-CD 3 September 9, 2011 16:54
Discussion: Reason of Turbulence!! Wen Long Main CFD Forum 3 May 15, 2009 10:52
what is fully developed turbulence? sarah_ron FLUENT 0 October 23, 2006 16:25
Help: what is fully developed turbulence? sarah_ron Main CFD Forum 1 January 9, 2005 09:09


All times are GMT -4. The time now is 20:11.