Eddy Taxonomy Methodology around a Submerged Barb Obstacle within a Fixed Rough Bed
Publication: Journal of Engineering Mechanics
Volume 131, Issue 10
Abstract
Past research in environmental hydraulics has established the consideration that small- and large-scale turbulent eddy structures correspond to fast and slow fluctuations within a velocity time series measured at a fixed location. This work embraces this concept and develops an eddy taxonomy methodology to classify the prominent small- and large-scale eddies in the vicinity of an obstacle within a fixed rough bed. The previously documented visual interpretation technique is used in conjunction with a novel technique, which utilizes the statistical skew parameter, to quantify the moving-average time step at which large-scale eddies may be isolated from small-scale eddies. Thereafter, triple decomposition theory is employed and prominent spatial and temporal scales (i.e., integral length scales and periodicity) of small- and large-scale eddies are calculated. The eddy taxonomy methodology is implemented using acoustic Doppler velocimeter time-series measurements captured in the vicinity of an experimental model of a submerged barb obstacle—a hydraulic structure used for bank protection and increasing aquatic diversity. Implementation of the eddy taxonomy methodology using the streamwise velocity time series and streamwise-vertical Reynolds stress time series provide similar results for the time step necessary to decompose large- from small-scale eddies. Eddy taxonomy results indicate the presence of large-scale, macroturbulent eddies throughout the barb test section with periodicity and length scales that agree with literature reported values. Additionally, small-scale bed derived eddies are most pronounced in the deflected flow regions where the barb obstacle has less influence upon the flow, while multiple small-scale eddies, including ejection, wake, and Kelvin–Helmotz associated eddies, persist in the downstream overtopping and wake regions of the barb obstacle.
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Acknowledgments
This research was funded by the Washington State Department of Transportation (Hydraulics Group) under WSDOT Grant No. UNSPECIFIEDT2696-03 to Washington State University. The writers would like to acknowledge the help/input provided by the WSDOT engineers Rose Peralta and Matt Witecki.
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Information & Authors
Information
Published In
Journal of Engineering Mechanics
Volume 131 • Issue 10 • October 2005
Pages: 1082 - 1101
Copyright
© 2005 ASCE.
History
Received: Jul 18, 2003
Accepted: Dec 7, 2004
Published online: Oct 1, 2005
Published in print: Oct 2005
Notes
Note. Associate Editor: Michelle H. Teng
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