碩士 / 國立臺灣海洋大學 / 河海工程學系 / 99 / The CBEM numerical model is used to calculate the changes in hydrodynamic characteristics (KD) of the harbor and the surrounding body of water, by analyzing the types of forward incident waves (regular and irregular waves) passing through offshore breakwater. The results are compared and presented at plane and cross-section. Offshore breakwater is composed of five impermeable and porous concentric cylinders, and irregular waves are simulated to Bretschneider, P-M, and JONSWAP spectra, which are separated by energy, frequency, and exponent methods. The variables are the distance of harbor basin export to offshore breakwater, and the dissipating parameter of the harbor boundary.
Impermeable offshore breakwater may be more effective than permeable offshore breakwater in reducing wave energy into the harbor. However, it is harder for the wave reflect caused by the impermeable offshore breakwater to get out of the harbor. Therefore, the wave energy might be accumulated in the harbor. For the surrounding water body, the wave height is lower when using impermeable offshore breakwater.
When regular waves forward inject, using impermeable offshore breakwater at the front of the harbor is tranquilest when it is 0.5 times of wave-length, whereas it is 0.75 times of wave-length for permeable offshore breakwater. For the tranquilest of harbor, there is no certain position and type of offshore breakwater when irregular waves forward inject, because it’s changed with different wave spectra and method of separate. The most suitable choice is the porous concentric cylinder, placed at the front of the harbor about 0.5 times of significant wave-length. Because the proportion of a longer period wave is greater than others when the JONSWAP spectrum is separated by the exponent method, the wave height in the harbor is higher than the others, and the harbor causes resonance when using impermeable offshore breakwater.
The wave height in the harbor is reduced when using dissipating parameter of harbor boundary, especially when using impermeable offshore breakwater. The dissipating parameter of harbor boundary can also reduce the problem of harbor resonance.
| Identifer | oai:union.ndltd.org:TW/099NTOU5192050 |
| Date | January 2011 |
| Creators | Chi-Hen Lee, 李其衡 |
| Contributors | Ching-Yun Yueh, 岳景雲 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 137 |
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