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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Water engineering : Estimate of lagrangian integral scales in shallow tidal water using high resolution gps-tracked drif...
Estimate of lagrangian integral scales in shallow tidal water using high resolution gps-tracked drifters
Author : KABIR SUARA(1)a, RICHARD BROWN(1)b CHARLES WANG(1)c, MICHAEL BORGAS(2) & YANMING FENG(1)d
ABSTRACT
In estuaries and natural water channels, the estimate of velocity and dispersion coefficients is critical to the knowledge of
scalar transport and mixing. This estimate is rarely available experimentally at sub-tidal time scale in shallow water
channels where high frequency is required to capture its spatio-temporal variation. This study estimates Lagrangian
integral scales and autocorrelation curves, which are key parameters for obtaining velocity fluctuations and dispersion
coefficients, and their spatio-temporal variability from deployments of Lagrangian drifters sampled at 10 Hz for a 4-hour
period. The power spectral densities of the velocities between 0.0001 and 0.8 Hz were well fitted with a slope of 5/3
predicted by KolmogorovĄ¯s similarity hypothesis within the inertial subrange, and were similar to the Eulerian power
spectral previously observed within the estuary. The result showed that large velocity fluctuations determine the
magnitude of the integral time scale, TL. Overlapping of short segments improved the stability of the estimate of TL by
taking advantage of the redundant data included in the autocorrelation function. The integral time scales were about 20 s
and varied by up to a factor of 8. These results are essential inputs for spatial binning of velocities, Lagrangian stochastic
modelling and single particle analysis of the tidal estuary.
File Size : 1,003,600 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Water engineering
Date Published : 18/08/2015
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