Recorded presentation12B.2
Curvature Imaging of Breaking Wind-wave Characteristics in the Laboratory
Brian K. Haus, Univ. of Miami/RSMAS, Miami, FL; and T. Hara
The amount of momentum flux induced by breaking waves is thought to contribute significantly to air-sea exchanges in high wind conditions. Recent models of these transfers incorporate parameterizations based on the breaker length, speed and the amount of coverage of breaking waves. To provide guidance on the appropriate values for these terms over a range of wind speeds a series of laboratory measurements were conducted. The capabilities of the Air-Sea Interaction Saltwater Tank (ASIST) at the University of Miami were exploited to observe breaking waves in winds ranging from 2-25 m/s. The tank has a 15 m long by 1 m wide test section that was filled to a height of 0.42m with fresh water. Innovative optical imaging techniques using convergences/divergences of light, which were related to local curvature were found to provide useful information on breaking wave crests. Stress and velocity profiles and wave slope spectra were also observed at two fetches for the same range of conditions. The height of the constant stress layer in the tank at a fetch of 5.95 m increased from 0.02 m to 0.14 m approximately linearly with wind speed. The proportion of light intensities that fell below selected curvature thresholds were closely related to the percent of breaker coverage. Breaker speeds were extracted by tracking the propagation of regions of small curvature radii. The breaker speeds and percent coverage were both observed to increase proportionally with wind at low speeds, as the winds became stronger the dominant wave scale also became important.
Session 12B, Laboratory studies of air-sea exchange processes
Thursday, 15 January 2009, 8:30 AM-9:45 AM, Room 128B
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