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

LES correlation and turbulent energy spectrum

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 13, 2005, 14:21
Default LES correlation and turbulent energy spectrum
  #1
Fabian
Guest
 
Posts: n/a
Hi,

I want to calculate the turbulent kinetic energy spectrum from my LES data to do one step in the validation process, but I am little bit confused about it.

There are two choices, one is to create a energy spectrum in space, where I have to find a homogenous direction, and the other to create a spectrum in time, where I have to choose a certain point in domain.

The problem is, which variant should I use and esp. which plane for the spectrum in space and which point in a surface-mounted cube simulation?

To calculate the spectrum I have to caculate the autocorrelation or cross-correlation, depending on the choice space/time. There exist an octave/matlab function 'xcorr' which can do that, but I would like to do that without using that function and without the use of FFT.

Would be nice if anybody has an idea!

Fabian

  Reply With Quote

Old   October 13, 2005, 18:07
Default Re: LES correlation and turbulent energy spectrum
  #2
sss
Guest
 
Posts: n/a
For space: invoke Taylor's frozen field hypothesis, For time: simply take FFT of the velocity signal
  Reply With Quote

Old   October 17, 2005, 01:32
Default Re: LES correlation and turbulent energy spectrum
  #3
Fabian
Guest
 
Posts: n/a
Hi,

thanks, do you have an idea which point (time) or plane (space) I should choose for a surface mounted cube calculation. I mean, I could try to find the best point which gives me Kolmogorovs -5/3 slope...

Fabian
  Reply With Quote

Old   October 17, 2005, 05:13
Default Re: LES correlation and turbulent energy spectrum
  #4
Lionel Larchevêque
Guest
 
Posts: n/a
In order to have a chance to find a -5/3 slope generally related to a wall-free turbulence at equilibrium, I suppose that the measurement point should be located in the wake and a few cube length away from the aft wall.
  Reply With Quote

Old   October 18, 2005, 02:04
Default Re: LES correlation and turbulent energy spectrum
  #5
Fabian
Guest
 
Posts: n/a
Hi Lionel,

thanks for the information. I see how this works.

Greetings! Fabian
  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
Ansys CFX 13, Turbulent flame speed correlation by Bradley ovechkin CFX 0 July 27, 2011 09:49
calculating of velocity auto correlation of solid particles in a turbulent flow mazdak Main CFD Forum 0 December 29, 2009 07:34
Can I add a correlation for turbulent Prandtl No. ? ananta Phoenics 3 November 10, 2009 05:35


All times are GMT -4. The time now is 01:26.