The Wavelet Digest Homepage
Return to the homepage
Search the complete Wavelet Digest database
Help about the Wavelet Digest mailing list
About the Wavelet Digest
The Digest The Community
 Latest Issue  Back Issues  Events  Gallery
The Wavelet Digest
   -> Volume 4, Issue 2


Preprint: Partitioning eddy motion using Lorentz wavelet filtering
 
images/spacer.gifimages/spacer.gif Reply into Digest
Previous :: Next  
Author Message
Brani Vidakovic
Guest





PostPosted: Mon Dec 02, 2002 5:42 pm    
Subject: Preprint: Partitioning eddy motion using Lorentz wavelet filtering
Reply with quote

Preprint: Partitioning eddy motion using Lorentz wavelet filtering

Preprint available:

The partitioning of attached and detached eddy motion in the
atmospheric surface layer using Lorentz wavelet filtering

By Gabriel Katul and Brani Vidakovic

via anonymous ftp: ftp.isds.duke.edu
/pub/brani/papers/
as
-rw-r--r-- 1 119 33 1996900 Feb 9 10:40 turbulwave.ps
or
-rw-r--r-- 1 119 33 574818 Feb 9 10:41 turbulwave.ps.Z


Abstract:

Townsend's (1976) attached eddy hypothesis states that the
turbulent structure in the constant stress layer can be decomposed
into attached and detached eddy motion. This paper
proposes and tests methodology for
separating the attached and detached eddy motion from time series
measurements of velocity and temperature.
The proposed methodology is based on the time-frequency
localization and filtering capabilities of the orthonormal wavelet
transforms. Using a relative entropy statistical measure, the
optimal wavelet basis is identified first. The turbulence time
series measurements are then transformed into the wavelet domain
where the contribution of specific events in the time-frequency
domain are identified. The filtering scheme utilizes a recently
constructed Lorentz thresholding methodology that successfully
eliminated all wavelet coefficients associated with the detached
eddy motion. While this filtering scheme lacks the compression
efficiency of the classical Donoho and Johnstone's universal
thresholding model, it conserves the higher-order statistics and
important turbulence interactions related to the Reynolds stresses.
Following the filtering scheme, the attached eddy motion time
series is re-constructed by an inverse wavelet transform of the
non-zero wavelet coefficients. The proposed partitioning
methodology for attached and detached eddy motion is tested using
$56 Hz$ triaxial sonic anemometer velocity and temperature
measurements above a uniform dry lake bed in Owens valley,
California, for a wide range of atmospheric stability conditions.
Validation that the wavelet filtered time series represented the
attached eddy motion is also discussed in the context of
conservation of turbulence energy and surface fluxes.
All times are GMT + 1 Hour
Page 1 of 1

 
Jump to: 
 


disclaimer - webmaster@wavelet.org
Powered by phpBB

This page was created in 0.025018 seconds : 18 queries executed : GZIP compression disabled