碩士 / 國立臺灣大學 / 工程科學及海洋工程學研究所 / 102 / The bathymetry and strong oceanographic variability in shallow water area can contribute to horizontal refraction. A wavefront obliquely incident upon an ocean front can be refracted in a direction dependent upon the angle of incidence and the modal phase speed which is determined by the horizontal wavenumber of the mode. This refraction on the horizontal plane causes convergence or spreading of acoustic energies and characterizes as the 3D effect. In this thesis, a hybrid underwater acoustic propagation model (Three-Dimensional acoustic propagation model of horizontal Gaussian Beam and Vertical Normal Mode, abbreviated as 3DGBM-M) based on the approach of horizontal rays and vertical modes is developed to interpret the horizontal refraction. The horizontal rays are calculated by the Gaussian beam method, in another word, the Gaussian beam method is used to calculate the modal amplitudes of vertical local modes. The Pekeris waveguide case is used as the benchmark to verify this hybrid model (3DGBM-M) for 2D propagation. The shallow water regions with sand dunes are modelled by adding sinusoidal variation to the ocean bottom in a Pekeris waveguide, and the underwater acoustic propagation in this region are calculated with 3DGBM-M and compared with the results calculated by wide-angle version of FOR3D. This hybrid model, 3DGBM-M, offers an robust solution to three-dimensional underwater acoustic propagation with improvement in spatial resolution, a result of using the Cartesian coordinates instead of the cylindrical coordinates, and high computing efficiency.
| Identifer | oai:union.ndltd.org:TW/102NTU05345038 |
| Date | January 2014 |
| Creators | Yu-Chen Cheng, 鄭郁蓁 |
| Contributors | Chi-Fang Chen, 陳琪芳 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 56 |
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