Observations of the spatial distribution of bubbles generated by breaking waves
| dc.contributor.author | Crawford, Gregory Blair | en_US |
| dc.date.accessioned | 2024-08-13T18:16:20Z | |
| dc.date.available | 2024-08-13T18:16:20Z | |
| dc.date.copyright | 1985 | en_US |
| dc.date.issued | 1985 | |
| dc.degree.department | Department of Physics | |
| dc.degree.department | Department of Physics and Astronomy | |
| dc.degree.level | Master of Science M.Sc. | en |
| dc.description.abstract | This thesis represents a study of the spatial distribution of sub-surface bubbles generated by breaking wind waves. Observations of bubbles were obtained using an upward-pointing acoustic transducer mounted on a submarine. Experiments were carried out about 10km off the coast of Monterey, California at wind speeds of about 3ms-l to llms-1. For the first time, estimates of the concentration of bubbles, N, have been determined from acoustic backscatter levels. The measurements are also unique in that they represent two-dimensional profiles of N, indicating both vertical and horizontal dependence. At low wind speeds, few identifiable patches of bubbles were observed. At higher wind speeds, the concentration of bubbles was observed to increase. In addition, the depths to which bubbles penetrate increased with wind speed. Mean vertical profiles of N indicated an exponential dependence on depth, which is consistent with a simple one-dimensional diffusion model. The mean bubble concentration at the surface, N, was found to increase with wind speed u10 as N0~U10(3.0±0.3). Estimates of thee-folding scale, ze, increased in general with wind speed, but the level of convective turbulence also influenced the values of ze. The bubble plumes were found to be more columnar when the air-sea temperature difference was more negative (i.e. when the level of convective turbulence was greater). Ratios of the horizontal extents of bubble plumes, as measured at different angles to the wind direction, were found to be consistent with the ratio of the horizontal scales over which waves break on the ocean surface. A data set collected while travelling in the downwind direction was found to have a spectral peak corresponding to a separation of 45m between bubble plumes, consistent with the expected spacing between breaking events on the surface. These results provide evidence that the bubble plumes are directly related to breaking waves on the ocean surface. | |
| dc.format.extent | 118 pages | |
| dc.identifier.uri | https://hdl.handle.net/1828/17549 | |
| dc.rights | Available to the World Wide Web | en_US |
| dc.title | Observations of the spatial distribution of bubbles generated by breaking waves | en_US |
| dc.type | Thesis | en_US |
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