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Breaking wave turbulence in the surf zone /

by Sweeny, Margaret E.; School (U.S.), Naval Postgraduate

Abstract (Summary)
An increasingly exercised and precarious region of the maritime battlefield is the surf zone. Wave properties and turbulence dissipation from breaking waves in the surf zone were calculated from data collected during the 2001 RIPEX/ Steep Beach Experiment. Wave characteristics, such as current velocities, period, significant wave and sea surface height, and tide were examined. The tide was shown to have the major influence on the breadth and the location of the surf zone from the shoreline. Video imaging time series were geometrically transformed into plan views of pixel brightness related to wave breaking intensity. Surf zone boundaries were generated using both a computer algorithm and manual manipulation. Two methods were examined for calculating breaking wave dissipation rates for particularly robust days (110.5 -114.5). Velocity data were acquired using two electromagnetic current meters over the vertical mounted on a tower at mid-surf zone. The first method identified individual bores, which were ensemble averaged by phase over 30 minute records to obtain wave number spectra invoking Taylor's frozen turbulence hypothesis. Maximum dissipation rates underneath the bore cycle were shown to lag behind the sea surface elevation. The second method used 30 minute ensemble averaged spectra to obtain dissipation after Trowbridge and Elgar (2001). Dissipation rates calculated underneath each bore segment were orders of magnitude smaller when compared to the ensemble averaged technique.
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School:The United States Naval Postgraduate School

School Location:USA - California

Source Type:Master's Thesis

Keywords:ocean waves turbulence

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